Intelligent materials are the materials possessing the following function in themselves such as the sensing function which detect the environmental change or their inner anomaly, the processor function which can judge the situation to lead the conclusion, and actuating function that the materials themselves can take action or give instruction. The structural and functional materials simply utilize the native properties and functions of their own. On the other hand, the intelligent materials are based on a new concept where the information science will be united with their own properties and functions. The intelligent materials can be very important and useful in many fields and their interdisciplinary fields such as the medicine, pharmacy, bioengineering, polymer, metalugy, semiconductor, ceramics, electronics, machinery. It is also extremely important in the human engineering, safety engineering, environmental study and study on the resources. In this report, the category of the intelligent material and the recent activities of researches on the intelligent materials are discussed.

Engineering structures and systems such as transportation vehicles are made of structural materials which generally only have a passive function. All sensing, control and actuation required to make these vehicles move has originated from biological creatures. Human beings have always kept the major role of sensing and control while animals have initially been mainly selected to take over the actuation part. This fundamental fact, which is based on the nature to survive, has been the driver for all following technological development.

An old-rooted endeavour of man, i.e. fabrication of material and structures taking inspiration from nature, is again actively pursued under a renewed name: biomimesis. This approach, once belonging to the realm of biological sciences, is based on the observation that, when one tries to embody our recognition criteria for biological organisms in an explicit list, nothing can be found on that list that cannot be mimicked by some inorganic system. Hence, a large variety of artifacts can be made, all possessing, to some extent, life-like features. Biomimetic arguments are today common reasoning in experimental studies about `origin-of-life' and in `advanced robotics'; a relatively new entry pertains to the area of `material science'.

Considerable research attention has been focused recently on materials which change their structure and properties in response to external stimuli. These materials, termed `intelligent materials', sense a stimulus as a signal (sensor function), judge the magnitude of this signal (processor function), and then alter their function in direct response (effector function). Introduction of stimuli-responsive polymers as switching sequences into both artificial materials and bioactive molecules would permit external, stimuli-induced modulation of their structures and `on-off' switching of their respective functions at molecular levels. Intelligent materials embodying these concepts would contribute to the establishment of basic principles for fabricating novel systems which modulate their structural changes and functional changes in response to external stimuli. These materials are attractive not only as new, sophisticated biomaterials but also for utilization in protein biotechnology, medical diagnosis and advanced site-specific drug delivery system.

New materials have been emerging in the industry for several decades. Recently, the research into materials has spread; the development of university and industrial laboratories, the use of physic and chemistry for their design give a new impetus to this research. A material apparently as common as concrete is no exception to this general trend. However, the economic aspect of research much always be kept in mind and performance objectives selected with discernment.

Intelligent materials may simply feature structural integration of sensing, infonnation processing and actuatmg capabilities, although they have been described in various manners from different viewpoints'. The conventional design concept of focused on the structure-function cofrelation to realize unit-function. Several material designs have been aimed at multi-functionality by hybridizing atid compositin elemental materials. Built-in functions, however, have never been coordinated within thematerial. In contrast, the concept of intelligent materials is to install software capability for coordinating or to integrate such unitfunctions as sensing and actuating.

Nanoscale layers of conducting polymers were prepared around redox enzyme molecules on electrode surfaces and were applied to electric interfaces to perform the smooth electron transfer between the redox proteins and electrodes. The interface design might be useful to bind the functions of both biocatalysts and electronic materials and to develop intelligent devices.

A nonequilibrium version of the charge-conformational interactions is presented in order to substantiate the synergetic modes of the functioning of biological charge transport systems as molecular switches, processing fluxes of charges.

The effect of phase transition of a thermosensitive matrix on temperature dependencies of observed activity, equilibrium, and kinetic constants of the enzymatic reaction was studied using (alpha) -chymotrypsin immobilized into thermosensitive poly-N-isopropylacrylamide gel as a model system. The behavior of the system is determined by the properties of the enzyme at temperatures less than critical temperature corresponding to phase transition of the polymeric gel but by the properties of the thermosensitive polymeric matrix at temperatures higher than that critical temperature. The phase transition of the thermosensitive gel was shown to affect weakly temperature dependencies of equilibrium parameters of enzymatic reactions. All reversible effects of the reduction of the enzymatic activity at high temperature are exclusively due to the changes in temperature behavior of kinetic parameters of the enzymatic reaction.

We present first results on thin film metal deposition on the regular bacterial surface layer of Sporsarcina urea by pulsed laser deposition. To prevent structural damage of the biological specimen a recently developed cross beam technique is applied providing an effective filtering of the most energetic plasma particles. The deposited films are examined by low voltage scanning electron microscopy. The surface profile of the S-layer adsorbed onto mica substrate was investigated by atomic force microscopy. A lattice constant of 13.2 nm has been measured. The lattice parameters and the structural appearance of the protein layer is in reasonable agreement with the results of an electron microscopical 3D structural analysis.

Two different kinds of collagen assembly have been studied: the reconstitution of type I collagen to fibrils and the formation of 2D networks on surfaces. The kinetics of fibril assembly are influenced by polyaspartate, as measured turbidimetrically. Addition of polyaspartate increases the fibril diameter. The reconstituted fibrils are imaged by atomic force microscopy and scanning electron microscopy. The preparation of thin collagen films on highly oriented pyrolytic graphite leads to networks or tree like structures depending on the collagen concentration in the precursor. The results presented are of interest for the development of new bone-like implant materials and the covering of bone grafts with a biocompatible layer.

In contrast to the unsuccessful efforts of many investigators to reduce underwater drag by the use of thin compliant coatings designed to simulate dolphin skin, it was suggested in prior publications in this series that the dolphin's delay in the onset of boundary layer turbulence and reduced drag results from the `intelligent' properties of the thick blubber underlying its skin. The blubber is supposed to have viscoelastic properties such that the dolphin acts as a compliant layer load of mechanical shear impedance, Z_L, which matches the impedance, Z_G, of incipient boundary layer turbulence acting as an equivalent shear force generator. Under this matched condition maximum power transfer and energy absorption in the blubber then quenches continued boundary layer turbulence and restores laminar flow. A gel-foam composite with frequency variations of complex shear compliance and shear modulus close to those of dolphin blubber is described, and suggested as a composite system for use in thick compliant material coatings for drag reduction.

Health monitoring of composite materials would give improved durability and safety of composite structures. Much effort has been performed in the past to obtain information on the health of e.g. aircraft structures. However, it can yet not be foreseen which monitoring technology will be used. This paper will give an overview on same selected technologies available, with a special emphasis on electrical methods.

Thinking about intellectualization of nondestructive inspection, the author found that maintenance inspection was the most beneficial one of applying health-monitoring concept. The goal of this new smart maintenance inspection is; continual monitoring and self-, automatic-inspection and warning, instead of inspection periodical and by many hands and slow-results obtaining today. On this new, smart maintenance inspection, the author presents a method and its problems.

A brief overview of the qualitative nondestructive evaluation techniques developed at the Center for Intelligent Material Systems and Structures is presented. The principal goal of the three techniques (impedance-based, laser Doppler vibrometer-based, and particle tagging) is to detect, on-line, incipient damage before the structural integrity is affected. By providing a better assessment of the structure, these real-time health monitoring will significantly reduce maintenance costs.

Frequency dependent dielectric measurements (FDEMS) provide a sensitive, automated in situ sensor for intelligent processing and an in situ means for monitoring durability, that is degradation of polymers during use. FDEMS in situ sensors can be designed and calibrated to monitor changes in processing properties during fabrication and changes in mechanical or electrical service life properties of polymer materials during use. With a proper understanding of the type of polymer and the use environment, the sensor output can be related to changes in modulus, maximum load and elongation at break. The FDEMS technique has advantages over other monitoring techniques: nondestructive; accuracy/reproductivity; sensitivity; in situ capability; remote sensing; automated.

This paper presents a concept for a built-in diagnostic system for detecting impact damage in in-service composite structures. The proposed system consists of two major diagnostic processes: passive sensing diagnosis (PSD) and active sensing diagnosis (ASD). The PSD utilizes the sensor measurements to determine the impact force and predict the location of the impact. The ASD generates diagnostic signals from the actuators to estimate the size of the impact damage resulting from the impact. In PSD, a computer code, `IDIMPACT,' has been developed for identifying impact force and location using distributed sensor measurements for both metallic and composite plates. For active sensing diagnosis, current work is focused on developing diagnostic methods based on the propagating waves. A key development for this work is to construct appropriate diagnostic waves for effectively detecting impact damage.

Recent high visibility aviation accidents have led to increased research into the use of sensor technology for monitoring aircraft structural integrity. To this end this paper describes applications to crack growth, multiple interacting flaws, and composite repairs.

Specific characteristics of Lamb waves, and more particularly their ability to propagate over long distances, make them a promising technique for health monitoring of composite structures using piezoelectric transducers bonded on the surface or embedded inside the material. In order to evaluate the possibilities of the technique, a theoretical dispersion model for the Lamb waves propagation has been realized for a carbon-epoxy composite material, and the control parameters, incidence angle, emission mode and frequency, have been fixed. The technique has then been experimented in a transmission mode with contact conversion mode transducers. The propagation over long distance and the detection of delaminations have been put in evidence. Then, optimized transducers have been manufactured in order to instrument, first, monolithic composite structures using surface bonding, and second, sandwich structures with embedded elements in the bulk. Experimental results show that a large network could be envisaged. This technique presents serious interests compared to conventional ultrasonic techniques, testing at a point, or passive measurements of local stress and strain modifications due to the delamination.

Recently, smart composites have appeared as new materials. But, these materials require the integration of functional elements within the composite structure which generates some problems. This paper demonstrates how carbon fibers are not only the reinforcement but also the sensor to detect in-situ damages in CFRP laminates. (+/- 45 degree(s)) laminates were subjected to monotonic and creep tests under three-point bending conditions. The in-situ monitoring of electrical resistance variation and AE activity allowed the detection and the identification, at different stages, of various types of damage mechanisms (not only fiber fractures but also matrix cracks, debondings and delaminations).

Localized stress/strain measurements in polymer based composites can now be made using a laser Raman sensor. In this case the stress sensor is the reinforcing fiber of the composite and the detector is the Raman spectrometer. Measurements can be conducted in reinforcing fibers near the surface of laminates. For measurements in the bulk of composites, the exciting laser light has to be transported to the reinforcing fibers via an embedded fiber optic cable. The backscattered light is transmitted through the same fiber optic and is sent to the Raman spectrometer for analysis. The effect of the direction of the fiber optic cable with respect to the axis of the reinforcing fibers is examined. Finally, the relationships between the local fiber stress or strain obtained from the Raman sensor and the far field stress or strain measured conventionally, are established.

Lamb waves are used in the non destructive evaluation of composite materials as they can propagate over long distances. The usual method of generation relying on a transducer that can not be reduced to a low thickness (oblic incidence transducer), the development of a thin transducer using a comb-like array of piezoelectric elements has been investigated. It requires a deep understanding of the dispersion relations in the material, in order to determine its geometrical parameters for a set of frequencies. Then, a prototype designed to work on surface is presented and Lamb waves generation is compared with classical oblic incidence sensors.

The piezoelectric implant method has demonstrated its efficiency to monitor the mechanical properties of polymer based materials and in particular to follow in situ curing and ageing phenomena. From the electrical impedance of a piezoelectric plate inserted in the material to be tested and using an optimization algorithm, we have shown previously that it is possible to determine two acoustical parameters of the material: the attenuation and the velocity of the ultrasonic waves. This paper deals with the influence of different defects (non parallelism and debonding) on the validity of these results. Thanks to a model, and using the Kramers-Kronig relations, the defect that does not disturb the correct use of the identification process were evaluated.

Theoretical considerations show that the electrical impedance of a piezoelectric element depends on the physical and geometrical properties of the element and also on the viscoelastic characteristics of the different media surrounding it. According to a dynamic model, an original technique has been developed by inserting a piezoelectric ceramic in the composite structure when processed. The electric signal, after signal processing and numerical treatments, gives access to the viscoelastic properties of the external medium. This method is an excellent indicator to display the curing kinetics of the resin as well as the post-curing phase of the composite structure process. Moreover, a further application of this non destructive method is the monitoring of the hydrolytic degradation of the composite structure. The evolution of the electrical impedance of the piezoelectric sensor is presented here as a function of water exposition time for different polymer-based composites and compared to classical ultrasonic and rheological measurements.

Two self-forming and repair polymer cementitious composites were developed over a decade apart by the author. Both relied on a nature based paradigm as a model for building, in particular bone formation, repair, and degradation. For the first composite, the proposed material accreted from the ocean, made from a fluids based chemistry, that of seawater. The land based system was not built in-situ but relied on a man made supply of materials which were self-forming, self-repairing and dissolving. But in both cases a fluid based chemistry was necessary for self-building, repair and recycling of a bone-like composite material.

Glass reinforced plastic (GRP) and carbon fibre reinforced plastic (CF'RP) laminates are durable, versatile and light-weight materials which are progressively replacing metals traditionally used in aerospace, automobile, rail, gas-storage and many other industries. If these composite structures were to debond, fracture or seriously degrade whilst in-service, public injury or catastrophic failure could result. Therefore, in-service condition monitoring techniques for composite structures are most significant and are of immediate importance.

The concept of intelligent material/structure, largely debated for a few years, is generally applied to systems able to react to internal stimuli (selfcontrol) and external ones (adaptation to environmental conditions) in order to realize in the best way the function for which they have been designed. These systems include, in the most general case, sensors, actuators, bonded to the surface or integrated in the bulk of the structure, and a control unit. ONERA (Office National d'Etudes et de Recherches Aerospatiales), as other research institutes for aeronautics and aerospace, has undertaken for years important studies on intelligent vibration control of structures, at the Structures Department. More recently, at the Physics Department, we started investigations on the smart non destructive evaluation of composite aeronautical structures, typical materials being laminates carbon/epoxy, a few millimeters thick. As the sensors we intend to use are either optical fibers or piezoelectric ceramics, we have had to study their integration in the material. If the incorporation of optical fibers has been the object of numerous investigations, on the contrary, the integration of piezoelectric elements has been rarely tackled. The objective of this paper is to present the study we have started in this field, which we consider to be a critical one, and on which depends the future development of intelligent/smart structures. After a short bibliography, we give first a brief description of the integration of optical fibers, carried out at our laboratory and, second, a more detailed study of the embedment of piezoelectric elements in a stratified composite, including a technological part and a theoretical part.

A technique for easy installation and usage of optical fiber strain sensors is presented. This technique allows reliable and accurate fiber positioning by means of a resin support in which optical sensing leads are embedded. Static and dynamic behavior of the optical strain gauge is investigated and its performance is compared to similar optical sensing systems either directly surface mounted on the structure or embedded into composite laminates. Comparisons to values derived from a semiconductor electrical strain gauges are also made.

A new dual wavelength digital spatial domain multiplexing technique for optical fiber sensor array is reported. It can integrate a large number of sensing fibers and as well as dual- wavelength method into a simple, robust and low cost system. It greatly enhances the capacity of tracing fast varying measurands and the absolute measuring range of strain with the digital spatial domain multiplexed sensor system. Preliminary experiments have shown the feasibility of the technique.

Simple fiber-optic sensor for temperature measuring, based upon the temperature-dependent bend losses in plastic clad silica optical fibers, is being proposed. The quantity of light energy transmitted along the fiber depends on the numerical aperture of the fiber, i.e. the refractive index difference between the silica core (n₁) and the plastic cladding (n₀). On the one hand, the refractive index of polymer cladding n₀ for plastic clad silica optical fibers exhibits considerably temperature dependence. On the other hand, local aperture in fiber bend region also changes at strong curvature, which reduces the number of guided modes and respectively decreases the transmitted light power. Interaction of these two effects produces great dependence of light output energy on temperature. High sensitivity over a wide temperature range (at least from -20 degree(s)C to +60 degree(s)C) can be obtained.

Embedded fiber-optic sensors offer an attractive method for real-time in-situ characterization of composite materials. The present work is directed toward the development of an appropriate optical waveguide and sensing technique for high temperature ceramic applications. The waveguide consists of a sapphire optical fiber core and polycrystalline alumina cladding. The sensing technique is based on spatial intensity modulation induced within multimode optical fibers. This paper presents a brief description of the optical waveguide fabrication, a theoretical model for spatial intensity modulation (SIM) and experimental verification of SIM in sapphire fibers.

The concept of using embedded sensors based on optical fibre technology for condition monitoring in fibre reinforced composites is no longer novel. Extensive literature is available on the topic, and several development programmes have demonstrated concept feasibility. No routine service application has yet been reported. An interdisciplinary team in Israel, comprising industry and academic partners, has been developing various aspects of the technology, with the ultimate aim of real time monitoring of aircraft structural components during flight. Aspects studied have included optical signal processing and analysis, optical signal correlation with mechanical loading, micromechanical modelling of composites containing optical fibres, optical fibre to composite matrix stress transfer and techniques for embedding optical fibres during conventional composite manufacturing processes.

The bending deformation and matrix cracking were investigated by conducting a four-point bending test for a cross-ply composite beam with an embedded fiber optic Michelson sensor. The fiber optic Michelson interferometric sensor was constructed and embedded in the composite beam. The failure of composite beam, due to the matrix cracking, was successfully detected by the fiber optic sensor and the matrix crack in the composite beam was confirmed by an edge replica method. The characteristics of the failure signals from the fiber optic sensor were studied. The strain and failure signals of the composite beam were separated by digital filtering of the signal from the fiber optic sensor. The failure was obviously detectable by the failure signal filtered from the optical signal.

The effect of embedded optical fibers on the static and fatigue interlaminar shear strength of a glass reinforced polyester laminate is evaluated. Seventy identical specimens with and without embedded optical fibers were tested researching more than 500,000 cycles in some cases. It was found that the optical fiber does not have a negative influence on the laminate, neither static nor in fatigue. These tests were included into a project to develop smart wind turbine blades.

One of the most important tasks in achieving a reliable performance of embedded optical fiber sensors in aircraft health monitoring and usage systems is to clarify their function reliability. In this study the limit of reliable sensor function is addressed for a number of loading conditions at room temperature. For static tensile loading the function strain limit for EFPI- sensors was approximately 0.20%, whereas the function limit of embedded Bragg grating sensors was above the strain level (0.4 - 0.5%) for initiation of matrix cracking in the laminate. In compression the function of the EFPI-sensor was unimpaired to a strain level which was about four times larger than that in tension. In constant amplitude fatigue loading the function strain limit of the EFPI-sensor was similar to that in static tensile loading, i.e. 0.20% at 10⁵ cycles. The silica glass/polyimide coating interface in the EFPI-sensor was identified as the sites where failure was initiated. The finite element analysis showed that the effects of curing stresses and moisture in laminates have significant influence on the function reliability of sensors. The stress concentrations on the interface caused by the cavity in the EFPI-sensor are the main reason for the lower reliability obtained for the EFPI-sensor than for embedded Bragg grating sensors.

An optic fiber sensor based on the intermodal interference principle was integrated in a composite material structure to detect impacts and vibrations. Six fibers were integrated at the top of a carbon/epoxy composite panel and arranged to form a regular network on the structure. A series of impacts at various positions on the plate were performed using an instrumented hammer. The spectral responses of the optic sensors were compared to a reference piezoelectric accelerometer. Moreover a determination of the impacts position was performed with the arrival times measure of the generated acoustic wave front to the optic sensors. These tests proved the great sensitivity of this type of sensor, its integration easiness and the possibility to localize an impact on composite structures with a very simple device.

The phenomenon of core crush encountered in the aerospace industry during manufacture of co-cured composite panels has been explained. An experimental program which relied on direct measurement of pressure within the honeycomb core using an optical sensing technique has been used in conjunction with experimental observation and numerical modeling to determine the sequence of events which lead to this costly problem. Having understood the issue, it is now possible to take steps to reduce or eliminate the occurrence of core crush.

Society's demand for the development of new types of information gathering systems is very strong, and corresponds in part to intelligent sensors, containing systems for the numerical treatment of information using sensitive elements composed of intelligent materials. The relational difficulties that exist between fundamental research and different socio-economic environments on the one hand, and those existing between scientific disciplines on the other hand significantly limit creativity in this extremely promising area. The implementation of a science of structural relations favoring interdisciplinarity is the only possible guarantee of the establish of dynamic research in this field, which is at the interface between fundamental science, engineering sciences and technology.

The solid state memory effect, known as persistent photoconductivity is described in terms of electronic configurations of impurity centers in narrow-gap semiconductors. The studies of resistivity and magnetic susceptibility of compensated bulk single crystal PbTe:Ga present strong evidence that the dopant centers produce two types of electronic states: a shallow and delocalized paramagnetic level associated with the normal substitutional site configuration and a more localized non-magnetic level arising from a lattice distortion at or near the donor. The metastable properties of the impurity centers suggest a redistribution of electrons, 2Ga⁰ Ga⁺ + Ga^-, where, rather than all donors being neutral, half the Ga atoms have two electrons and become negatively charged whereas the other half have none and are positively charged. The potential areas of application of these intelligent materials are discussed.

The germanium (Ge) films of nanostructures deposited at 300 and 77 K by the cluster-beam evaporation technique are found to consist of small nanostructures. The crystal structure of the films is not the ordinary diamond but tetragonal structure. The Ge film deposited at 77 K exhibits photo-oxidation and blue-light emission when it is exposed to UV light. It may be said that the material possesses an ability to sense the environment and change in response to a change in the environment, which is one of the functions of intelligent materials. It, however, never restores itself even if an external stimulus (UV light in this case) is removed. Nevertheless, because of the unique crystal structure and optical properties of the Ge films, there is a possibility that further study may reveal their potential for intelligent materials.

A new type of photodetector is proposed in which the size and configuration of its photosensitive surface, as well as its sensitivity to the detected optical signal, are controlled by a special sensitizing light flux.

A Linear array Thin Film Position Sensitive Detector (LTFPSD) based on hydrogenated amorphous silicon (a-Si:H) is proposed for the first time, taking advantage of the optical properties presented by a-Si:H devices we have developed a LTFPSD with 128 integrated elements able to be used in 3D inspections/measurements. Each element consists on a 1D LTFPSD, based on a p.i.n. diode produced in a conventional PECVD system, where the doped layers are coated with thin resistive layers to establish the required device equipotentials. By proper incorporation of the LTFPSD into an optical inspection camera it will be possible to acquire information about an object/surface, through the optical cross- section method. The main advantages of this system, when compared with the conventional CCDs, are the low complexity of hardware and software used and that the information can be continuously processed (analogue detection).

A new concept for silicon microsensors based on porous EIS (Electrolyte-Insulator- Semiconductor) structures is presented. The porous sensor was prepared by anodic etching of n-doped silicon and subsequent deposition of a dielectric layer of SiO₂. Experimental conditions were investigated to realize a well-defined macroporous formation of the porous silicon. To compare the chemical sensor properties with similar built-up planar Si/SiO₂ structures, C/V (Capacitance-Voltage) measurements have been performed. The porous EIS structures have been characterized by SEM (Scanning Electron Microscopy), XPS (X-ray Photoelectron Spectroscopy) and cyclic voltammetry. This solid-state technology allows the preparation of transducer materials for pH microsensors.

The practical applications of chemical sensors based on ceramic sensing elements is strongly limited by the problems inherent to their sensing mechanisms. For gas sensors, the main problems of semiconducting oxides are the insufficient gas selectivity, the inability to detect very low gas concentrations, and changes in sensing properties caused by surface contamination. For humidity sensors, the factor which limits the market diffusion of porous ceramics is the progressive drift in sensor resistance, which makes a heat-cleaning treatment of the sensing elements necessary for the recovery of sensor performance. The problems encountered in using the conventional ceramic materials as chemical sensors are strictly related to their sensing mechanisms. Give that, the strategy to eradicate the problems is the exploitation of innovative sensing mechanism. Novel detection principals for chemical sensors can be obtained by materials having intelligent properties. Examples of multiphase systems for humidity and gas sensors are reviewed.

In this work, we propose solutions based on engineering of III-V heterostructures to develop new types of semiconductor magnetic sensors. These micro-Hall sensors use the properties of a 2D electron gas and the benefit of pseudomorphic material, in which both the alloy composition and the built-in strain offer additional degrees of freedom for band structure tailoring, to exhibit high magnetic sensitivity, good linearity, low temperature coefficient and high resolution. With the growth optimization which is described, two pseudomorphic In_0.75Ga_0.25As/In_0.52Al_0.48As heterostructures were grown on a semi- insulating InP substrate by molecular beam epitaxy. To understand better the influence of the heterostructure design on its electronic properties, a model involving the self-consistent solution of the Poisson and Schrodinger equations using the Fermi-Dirac statistics has been developed. These results have been used to optimize the structure design. A magnetic sensitivity of 346 V/AT with a temperature coefficient of -230 ppm/ degree(s)C between -80 degree(s)C and 85 degree(s)C has been obtained. The device show good linearity against magnetic field and also against the supply current. High signal-to-noise ratios corresponding to minimal magnetic field of 350 nT/Hz^1/2 at 100 Hz and 120 nT/Hz^1/2 at 1 kHz have been measured.

We constructed an ultrasonic carbon-fiber and investigated its characteristics for its application to electronic devices. That is, in the first part of this paper, are dealt with the construction of ultrasonic carbon-fiber and such ultrasound transmission characteristics as propagation speed, attenuation characteristics and phase. The second part contains the carbon-fiber gyro-sensor and its experimental results. It is found that judgement of revolution direction can be made possible by the prototype gyro-sensor, with relatively high sensitivity.

The increased utilization of various optoelectronic systems has generated interests in optoelectronic logical circuits with photoconducting (PC) and electroluminescent (EL) thin film devices. They are frequently applied as logical gates, amplifiers of weak light signals, and because of the optical feedback in such system, they can work as memory cells.

We present two new effects related to intelligent fluids. The first one is the control of the transmission of a laser beam by using the change of turbidity of an electrorheological fluid in the presence of an electric field. The second one is the control of the aggregation of non magnetic particles by a magnetic field in order to change the viscosity of the fluid. This fluid is made of non magnetic particles in suspension in a high magnetization ferrofluid.

An effective design methodology for ER devices requires reliable data to characterize the behavior of the ER fluid as distinct from the test device. In this paper the authors describe a technique they have used for generating ER fluid data so that it can be used to predict the performance of different types and sizes of device operating with the test fluid. The application of the technique is then illustrated using a problem of current industrial interest: namely the dynamic modeling of a controllable vibration damper for vehicle suspension applications.

Three new magnetic fluids, that haven't been previously reported, were chemically synthesized by improving the hydrothermal techniques. The fine particles ferrites were produced by coprecipitation and treated further in order to obtain stable ionic sols. Highly concentrated magnetic fluids (25% volume fraction) can be prepared by following the procedure described here. Characterization was performed using X-ray diffraction techniques.

Magnetic resonance is used to investigate magnetic interaction in magnetic fluids and magnetic agglomerates. Magnetic dipole-dipole interaction between monodomain particles accounts for the magnetic resonance data in magnetic fluids. In magnetic agglomerates however an anisotropic interaction between spins in the agglomerate and spins in the magnetic monodomain dominates the magnetic resonance behavior.

The magnetic anisotropy constant of magnetic fluids is obtained from the angular dependence of the magnetic resonance field. The sample was frozen below room temperature under the action of a steady magnetic field of 1.45 Tesla. Magnetic anisotropy of the order of -5.4 X 10⁴ erg/cm³ at 150 K and -5.1 X 10⁴ erg/cm³ at 200 K was obtained for a water-based MnFe₂O₄ magnetic fluid sample with average particle diameter of 10.7 nm.

Effects of waveform and frequency of electric fields applied to electro-rheological (ER) fluids are investigated on structural damping of a CFRP composite beam containing ER fluids. As the experimental results, the rectangular waveform is more effective for control of ER effects than the sinusoidal one. In vibration analysis, a simplified mass-spring-damper system is adopted to feature the first flexural mode of the cantilevered composite beam, where the damping factor is changed in time as a function of waveform which is applied to electric fields.

The unique properties of electrorheological fluids offer much promise both for the improvement of existing processes and for the development of a new generation of `smart' technologies and devices.

We have developed an electrically-driven chemomechanical system which shows quick responses with fish-like motility. Behaviors and principle of electrically-driven motion of the polymer gel have been studied. The principle of motility of this system is based upon an electrokinetic molecular assembly reaction of surfactant molecules on the hydrogel caused by both electrostatic and hydrophobic interactions. The cooperative binding of a linear as well as a cross-linked polyelectrolyte with surfactants has been theoretically analyzed. The general formulas derived on the basis of the free energy minimum principle predicted that the cross- linking enhances the initiation process but strongly suppresses the cooperativity due to the osmotic pressure in the network domain. The theoretical results showed fairly good agreement with the experimental data, confirming the essential features of the theory.

We have discovered that cross-linked polymer gels with hydrophobicity swollen in organic solvent undergo spontaneous motion when immersed in water. The mode of motion largely depends on the shape of the gel: a disc-shaped gel exhibits translational motion while a triangular or a square-shaped one exhibits rotation. The velocity and duration of gel motion are strongly associated with its size and chemical structure. The larger the gel, the longer the gel can keep motion. The mechanism of the gel motion on water has been investigated and we have found that the driven force of motion is from the surface spreading of organic solvent on water surface.

Lumped parameter models of non-electrolyte and electrolyte polymer gel based on the energy method are presented. Emphasis is placed on developing model that is simple enough for real time control implementation, yet able to capture essential inter-domain energy coupling effect. The dynamics of quasistatic polymer gel system are translated to bond graph representation.

Chemomechanical transformations are used to produce a mechanical force from a reversible chemical reaction in order to generate artificial muscular contraction, on the model of the biological muscle. The design and experimentation of an original artificial muscle using an ion-exchange polymer which reacts inside a soft envelope, derived from research on pneumatic artificial McKibben muscle, is presented. Then a chemomechanical actuator constituted of two artificial muscles has been conceived: first results are shown on position control in open-loop mode.

An electrochemomechanical device formed by a bilayer polypyrrole-non conducting polymer one side tape was studied in different concentrations of LiClO₄ aqueous solution. The artificial muscle was submitted to a constant anodic current of 15 mA or constant potential of 1000 mV vs. SCE. Chronoamperograms and chronopotentiograms were recorded meanwhile the free end of the bilayer crossed over an angle of 90 degrees. The consumed charge was constant whatever the electrical or chemical conditions were. The electrical energy consumed by the device movement decreased, at increasing concentrations of electrolyte, under galvanostatic control. The consumed energy remains constant under potentiostatic control but times required to cross over the 90 degrees decrease from 20 seconds to 6 seconds.

Several porous material systems (e.g.. hydrogels, conducting polymers, electrorheologic fluids) make possible a control of their properties in response to an appropriate stimulus (and viceversa) and therefore. they belong to the class of intelligent materials. In the present paper we propose a first classification of intelligent porous systems dividing them in three main classes: porous material as semi-permeable media, as reservoir and delivery systems and as biphasic composites with large interfacial area between solid and fluid phases. Then we present a continuos model to describe the passive mechanical behaviour of a generic porous conducting polymer saturated by a fluid. The model is solved for a stress-relaxation test and it is verified in the specific case of a doped polypyrrole porous matrix saturated by an electrolytic solution. The goodness of fit between experimental date and theoretical data confirms the validity of the model.

The electrical resistivity of polymer composites is studied as a function of temperature. The initial resistivity (rho) of thermoplastic or thermoset containing a metallic filler is in the range of 1 - 10 (DOT) 10^-2 (Omega) (DOT)cm. Around curing temperature of epoxies, the resistivity increases by eight to twelve orders of magnitude. For thermoplastic polymers, however, the transition temperature is related to the melting temperature at which a strong volume increase occurs. Hence, the choice of polymer and its processing determine the transition temperature from a conducting state to an insulating state. For a variety of polymers we have observed transitions between 80 degree(s)C and 200 degree(s)C. Due to a sharp and strong transition at a predetermined temperature, such materials can be used as temperature sensors. Since the resistivity of the cold state is low, they can also carry rather high currents. The balance between heating and cooling determines then a critical value for the current. Thus, the materials can also serve as a current sensors.

The stability of non-stoichiometric interpolyelectrolyte complexes (IPECs), which contain relatively long poly(methacrylate anion)s and relatively short poly(N-ethyl-4-vinylpyridinium cation)s, with respect to their dissociation into constituent polyelectrolytes in water-salt media was studied by fluorescence quenching and velocity sedimentation techniques. The dissociation of IPECs was found to begin at a certain critical salt concentration and to proceed by a gradual release of polycations from IPECs. The effects of polyion chain length and polyion charge density on the stability of IPECs were examined.

The composite material based on polyaniline and magnetite with magnetic loading up to 50 wt. % has been obtained. Nanometric size of magnetic particles leads to superparamagnetism of the composite. Analysis of the spectral characteristics indicates the existence of interaction between composite components.

Optical resolution of (alpha) -amino acids such as Tryptophan (Try) were carried out either by membranes or temperature-responsive polymeric adsorbents. Higher ordered supramolecular structures of polymers were recognized to be quite important for optical resolution by membranes. Optically active and temperature-responsive polymers derived from N-isopyropylacrylamide could be applied for optical resolutions of racemic Try by using dissolution-precipitation behaviors of the temperature-responsive polymeric adsorbents.

In consideration of the development of large area displays with improved electro-optical properties new functional materials were prepared based on polymeric supramolecular hydrogel networks. The highly ordered aqueous gel system is provided with particular properties for carrier material of electrically switchable polymerdispersed liquid crystals as well as for optical valve without assistance.'

The purpose of this paper is to describe and examine properties of light flux control materials. Indeed, intelligent light flux control is necessary not only to improve everyday visual convenience but also in an economical point of view in order to reduce global home energetic cost. Several types of materials are good potential candidates for such functions: (1) The most well-known investigations concern inorganic materials such as tungsten or molybdenum oxides in which an electrochrom layer darkens when enriched in ions, and looses its color when impoverished. Unfortunately, at the moment, there is no convenient way to realize correct ions suppliers. Moreover, other drawbacks arise, such as poor reversibility, reactive interferences or a sensitivity of the material to its environment. These systems only need a low voltage level to work. But, their dynamic response, which is correlated to the component surface, is quite long. (2) At the present time, another attractive issue seems promising. More and more studies concern micro-composite liquid crystal films. For first, we shall remind their principles as well as their way of preparation. After having talked about their main advantages as intelligent materials, we shall discuss their control, their light flux adaptability, or their memory capabilities.

The hypothetical structures of macromolecules with direct one-way excitonic conductivity have been examined. The dependence of excitonic current value on number of polymer's cell has been obtained for macromolecules of optimal energetical structure. Some compounds with direct exciton conductivity were designed and synthesized. Such compounds may be used as exciton convectors in nanoelectronics.

Theoretical approach to the fundamentals of write-read memory elements based on strain induction in optical materials and the basis of fotoelasticimetry is given. Manufacturing concept of the memory element with induced strain on polycarbonate and its realization is presented. We presented some earliest results in this domain. Applicability of the strain inducted memory is discussed.

The thermomechanical properties of a thin film of shape memory polymer of polyurethane series were investigated experimentally. The results are summarized as follows. (1) Modulus of elasticity and yield stress are high below glass transition temperature T_g and low above T_g. The value of loss tangent is large in the vicinity of T_g. (2) The stress-strain curves vary significantly in the early cycles but slightly thereafter under cyclic deformation above T_g. (3) During the heating process after loading above T_g followed by unloading below T_g, strain recovers in the vicinity of T_g. (4) Shape fixity with loading after T_g followed by unloading below T_g does not vary under thermomechanical cycling. Several applications of the polymer are introduced.

Dielectric spectroscopy is employed to study the dependence of the molecular dynamics of liquid-crystalline polyacrylates on the mesophase structure. The temperature dependence of the rate of the (beta) -relaxation which was assigned to rotational fluctuations of the mesogenic unit around its long axis can be described by an Arrhenius equation. Both the preexponential factor and the activation energy increase with the order of the mesophase which is discussed in the frame of the cooperativity of the (beta) -relaxation. It is shown that the activation parameters of this process correlate to lateral distance of mesogenic groups. The (alpha) - relaxation is related to the dynamic glass transition. Its independence on the mesophase structure is interpreted in terms of microphase separation. The rate of the (delta) -relaxation caused by rotational fluctuations of the mesogenic unit around its short axis is reduced by that of the (alpha) -process. The temperature dependence of this ratio is related to that of a molecular order parameter.

An aqueous polymer water gel as well as a microemulsion based gel (MBG) can be used as carrier material for dispersed thermotropic liquid crystals (LC). The LC droplet size in an aqueous water gel was dependent upon the emulsifying power. In a MBG the LC droplet size depends on the nature of the surfactant and the co-surfactant. Gel dispersed LC samples between two electrodes with a cell gap of 25 micrometers or 100 micrometers showed a scattering effect dependent upon application of an electric field.

Polymer Dispersed Liquid Crystals (PDLC) are materials formed by dispersions of liquid crystal (LC) droplets in a polymer matrix (1)• These materials are electro-optical active films which can be switched from a light scattering state (off state) to a transparent state (on state) by the application of a voltage (2)• The embedded mesophase within the droplets can be nematic (N), cholesteric (N*), chiral smectic C (SC*), or antiferroelectric (SCA*) (2)

This paper would like to draw the attention to the possibilities of tuning shape memory alloys for optimal use in smart materials. The importance of processing, transformation temperatures, hysteresis, texture is discussed. Finally, it is explained how the microstructure, by means of the presence of precipitates, can lead to dramatic but interesting changes in the E- modulus behavior during the martensitic transformation.

The thermomechanical properties of shape memory effect and superelasticity due to the martensitic transformation and the R-phase transformation of TiNi shape memory alloy were investigated experimentally. The transformation stress, transformation line and fatigue property due to both transformations were discussed for cyclic deformation. The thermomechanical properties due to the R-phase transformation were excellent for deformation with high cycles.

An extensive study of the effect of deformation, temperature and rate of deformation on the superelastic behavior of NiTi shape memory alloys wires was undertaken. This paper presents the first results. The temperature effect is to shift the stress-strain curve upward. It is generally believed that the strain rate sensitivity, sometime observed, is more a temperature effect due to the exo-endothermic transformations. In this research, the strain rate sensitivity of the transformation is demonstrated. Some interactions between the different variables are also shown.

Shape memory effect and intrinsic damping capacity (amplitude dependent internal friction ADIF) of Ti-50.6 wt.%Ni alloy have been investigated in different structural states (cold- worked, polygonizing and recrystallization, quenching). Relationship between `normal' plastic deformation due to the dislocation motion and deformation due to martensite transformation are discussed.

Among the different kinds of Smart Materials one of the more promising materials are the Shape Memory Alloys (SMA) because of their ability to perform two different tasks: "sensing and actuating" [1 ,2]. The thermomechanical properties of SMA with view of their use as smart materials have been recently reviewed [2,3]. Nowadays, three kinds of applications (active shape control, active modal modification and active strain energy tuning) based specifically on shape memory alloys are being developed [4,5]. Besides, in order to fulfil the increasing demand of smart materials with a large range of working temperature, several systems of SMA with higher transformation temperatures (until 240°C) are being explored, such as Ni-Al, Cu-Ni-Al, Fe-Mn-Si-X, Ti-Ni-Pd (see [6] for a review). Among them, Cu-Al-Ni shape memory alloys are firm candidates for applications between 100°C and 240°C because of their low cost, relatively easy processing and good shape memory properties. Nevertheless, due to their high elastic anisotropy (A13) and large grain size, the Cu-Al-Ni alloys are brittle, and in general show poor mechanical properties that should be improved in order to fulfil the requirements for practical applications. This improvement is usually accomplished through the addition of grain refiners such as Zr, Ti, B [7] to obtain a grain size lesser than 1OOm in diameter.

This paper analyzes briefly the different approaches to solve the problem of stresses generated by different thermal expansion coefficients, in brasing joints used to assemble high density electronic devices to printed circuit boards. While retaining certain ideas from some of the promising approaches, a novel approach to solve this problem is proposed in this report which involves developing a new composite solder paste containing superelastic alloy particles. Preliminary results obtained on Ni-coated NiTi wires embedded in a standard SnPb paste are reported which indicate that while the coated wires are wetted by the matrix, the adhesion between the coating and NiTi is poor. The behavior under tensile stresses have been simulated for NiTi particles incorporated composite pastes, each having a different particle volume fraction. Low strain value results show the decrease of the mean equivalent stress value when the volume fraction is increased.

The fatigue of TiNiCu and CuZnAl thin wires has been investigated during stress assisted two way memory effects thermal cycles. The influences of the number of thermal cycles and of the applied stress have been measured, and Wohler type curves are plotted. The evolution of the high and low temperatures shapes during the thermal cycling is also compared for the two alloys.

Due to an unusual macroscopic behavior, the shape-memory alloys lend themselves to innovative applications. Recently, a 3D constitutive model able to simulate the superelastic behavior has been proposed. The implementation of such a model within a finite-element framework is used here to perform the analysis of two shape-memory-alloy structures: a beam under four-point bending and a microstructure for the treatment of hollow-organ or duct- system occlusions (stent).

Among the potential materials for embedded actuators in composite smart structures, shape memory alloys are good candidates in many applications. Indeed they are able to produce large deformations and stresses. However, due to the complex and non linear behavior of these alloys, their use is often made by empirical way. The present paper gives some general results for the use of shape memory alloys in actuators.

A shape memory membrane actuator has been developed, which consists of stress-optimized microfabricated NiTi beam-cantilever devices of 100 micrometers thickness. For stress- optimization, the lateral widths of the beams have been designed for homogeneous stress distributions without local stress maxima, allowing a maximum use of active material for bending actuation. As a result, higher work outputs for a given stress level and smaller hystereses are obtained compared to non-optimized actuators with parallel beam-cantilever devices. Thus, improved hysteresis control is possible and better lifetime characteristics are expected. For a strain limit of 2% the achieved work output is about 24 (mu) Nm.

The most important actuator materials in adaptive structures are shape memory alloys, piezoelectric and magnetostrictive materials and electrorheological fluids. However, no such material is available which would produce rapid and large strokes with high forces. Shape memory alloys exhibit large strokes and forces but their response is slow. Piezoelectric materials and magnetostrictive intermetallics are rapid, but the strokes are small. In the present study, employment of magnetic control of shape memory effect as a principle for rapid large stroke actuator materials is discussed. In such materials, detwinning is controlled by an external magnetic field. Twins in favorable orientation to the magnetic field grow at the expense of other twins and cause a shape change of the actuator. Strokes can be as high as those in shape memory alloys, but response times are short due to magnetic control. Another method which may be applied in actuators is inducing the martensitic transformation and controlling the growth of the martensite plates by magnetostrictive distortions of giant magnetostrictive particles embedded in the shape memory alloy matrix. Magnetostrictive inclusions can also be used as stress sensors in shape memory materials. In pre-stressing and fastening applications, materials which exhibit large strokes and high recovery stresses are required. Nitrogen alloyed shape memory steels, developed for actuators for those applications, is the second topic of this study. In nitrogen alloyed shape memory steels, yield strengths over 1100 MPa and tensile strengths even 1600 MPa were attained. Recoverable strains can be over 4% and recovery stresses 330 MPa. Stresses over 700 MPa were achieved in fasteners at room temperature. Nitrogen alloyed shape memory steels possess good corrosion properties, machinability and weldability (even the welds exhibit shape memory effect). They are economical to manufacture and use and they are expected to have applications in many fields of engineering.

A fundamental model has been developed which allows to predict the complex thermomechanical behavior of smart materials composed of matrix materials with embedded shape memory elements. This model is based on a generalized thermodynamic analysis of the thermomechanical behavior of shape memory alloys. The mathematical approach and the assumptions in this model are selected in such a way that the calculation yield close approximations of the real behavior and that the final mathematical equations are relatively simple. Therefore, the modeling can be easily incorporated in a computer program. By several illustrations it is shown that this model can be used to calculate the thermomechanical behavior of complex cases.

The use of shape memory alloy fiber actuators to modify the natural vibration frequencies of a composite beam is investigated. A model system composed of an epoxy matrix with prestrained shape-memory-alloy fibers is used. The natural frequencies of vibration of the beam are measured in a clamped configuration. When electrically heated, the fibers undergo a reverse martensite-to-austenite transformation. Since the geometry of the fibers during the transformation is restrained by the constraints of both the matrix and the clamping device, a recovery force is generated. This force leads to an increase in the natural vibration frequency of the whole composite beam. The transformation behavior of the composite is compared to that of the neat fiber.

Bi-directional Environmentally Responsive Composites (ERC) composed of Ti-Ni alloy effectors and CFRTP (Carbon Fiber Reinforced Thermoplastic) were created in order to investigate the temperature responses and a method of responsive shape control of the ERC. Environmental responsiveness was defined as the responsiveness rate and the recovery rate corresponding to the change of environmental temperature. Responsive shape control was done by the controlling for the curvature of ERC, namely, when the mechanical properties and the initial curvature of the effectors were given and the curvatures of ERC at the low and high temperature were set, the equations were derived in order to calculate the initial curvature and flexural rigidity of the matrices. As a result, it was found that a bi-directional responsive ERC has superior performance could be made by appropriately choosing the properties, the geometries and volume fractions of effectors and matrices. The ratios of experimental and calculating values are very close on 1.0, the numerical results were fairly satisfactory ones.

Adaptive hybrid composites are materials in which actuators are embedded into polymer matrix composites. One particular class of these actuators are shape memory alloys. Thin wires ((phi) equals 200 micrometers ) of Nickel-Titanium-Copper (nitinol) were incorporated into a glass-epoxy unidirectional laminate during lay-up. Then the whole structure was subjected to different curing procedures. The interfacial shear strength between the matrix and the nitinol wires in various structural states was determined by a micromechanical test involving the interface directly--the drop test. Clamped-free (cantilever) beam method was used to evaluate the effect of actuation by heating the nitinol wires embedded into the composite. The comparison between the different composites points out first the leading role of the interfacial shear strength. On the other hand, it can be noted the occurrence of a self-trained two way shape memory effect.

This paper presents the first results obtained on a smart material element made of a shape memory alloy Ni-Ti fiber (without previous deformation) embedded in a resin epoxy matrix. When an electrical current is applied in the Ni-Ti wire, infrared camera permit to measure the surface temperature lateral faces. The integration of heat equation in a finite element code allows to obtain the local temperature of the resin and so predict its behavior. In the future for technological reasons (change of sample shape or resonance frequencies), the local stress- strain-temperatures fields will be obtained when heating a predeformed Ni-Ti wire embedded in resin produces recovery stress.

In his two papers Kafka (1994,1994a) presented a new approach to explanation and to mathematical modelling of shape memory effect and of pseudoelasticity. This approach was based on his general concept of modelling inelastic processes in heterogeneous media (Kafka 1987) and it was shown that this concept can successfiilly be applied even in the case where the heterogeneity under study is on the atomic scale, i.e. in the case of binary alloys and their shape memory behaviour. In the second quoted paper (Kafka 1994a) quantitative comparisons with experimental data received with samples ofNiTi alloy were shown and it was demonstrated that the unified mathematical model is able to quantitatively describe the shape memory effect as well as the pseudoelastic processes under different temperatures.

Piezoelectric 1-3 composites are being considered for sensor and actuator applications in smart structures. For the coverage of large surfaces, low-cost fabrication techniques for producing these new materials in large size panels were developed. In-air electromechanical characteristics and in-water acoustical properties of these new 1-3 piezocomposite panels were evaluated to assess the effects of temperature, pressure and underwater explosive shock on their acoustical performance.

The fluoridation of anionic sites in the perowskite lattice ABO₃ can greatly stabilize the remanent polarization under high stresses level. The dielectric losses are smaller than oxygen deficient materials. The mechanism for stabilization is always allocated to sites which can act either as electron donors or acceptors. The charge transfer induces a polarization which is sufficient to cancel the distribution of bound charge ((rho) equals -divP) in the poled phase. The B³⁺ - F^1- couples constitute dipoles which have a better stability than the B³⁺ - V₀ couples only present in perowskite ceramics with oxygen vacancies.

This study concerns the fabrication of a `soft' lead zirconate titanate (PZT) thick films on a Platinum substrate (5 X 15 mm size, 0.25 mm thickness) by the screen printing method. Various parameters connected with the screen printing (rheological characteristic of the ink, firing conditions of the layer) as well as those concerning the active powder used (grain size, grain distribution) are studied. The screen printed specimens characterized from their dielectric properties and their hysteresis loop show a diminution compared to the bulk ceramic, which may be attributed to the less than completely densified films. A study of the displacement versus an a.c. electric field of the piezoelectric film on a platinum substrate is also achieved by a laser doppler vibrometry technique. A comparison with a machined down ceramic pasted on this same Pt substrate is carried out.

This paper describes a fabrication approach for producing high-sensitivity low-cost accelerometers. This approach offers the potential for intrinsically combining accelerometers as a dense array within an actuator. Hence sensing and actuation functions can be combined into one co-formed inexpensive transducer array. Results are presented which show that the combined transducer has predictable properties and is well suited for use in sensing, actuation, and active-control applications.

The diffusivities of oxygen along the grain boundary in the PTCR-samples were greater than those in non-PTCR samples. The grain boundary diffusion characteristics drastically changed at the oxygen partial pressure of appearing the PTCR effect. On the other hand, the volume diffusivities of oxygen ions in both samples have the same value. These results lead that the structural change at grain boundary in polycrystalline barium titanate occurred at the oxidizing prossece and enhanced oxygen grain boundary diffusion. The origin of the barrier layer of the PTCR effect is considered to be same.

The measurement of shear stresses in the hydrodynamic boundary layer required high sensitivity sensors. A floating element type sensor using the piezoelectric effect is proposed. It is constituted of a composite material with high shear stress sensitivity. The evolution of the sensor characteristics with the PZT volume fraction is analyzed. The experimental results show a good agreement with the Finite Element Modeling predictions.

The dielectric nonlinear properties of ferroelectric materials are the main reason for their technical application. There is a wide variety of materials, e.g. liquid crystals, thin layers and even bulk-materials, that have these properties. One problem that must be solved before the technical application is to determine these properties to forecast the dynamical behavior. However, so far these parameters were determined in the case of zero excitation. This is a draw-back, because for the application of ferroelectric materials the large signal behavior is important. We want to solve a new way for determining the dynamical nonlinear properties of ferroelectric materials. We present a simple dynamical system, the dielectric nonlinear series resonance circuit, that can be used for studying the large signal behavior of the mentioned materials. With the help of a macroscopic model which contains the linear and nonlinear material-coefficients and a method that we developed recently, these parameters can be determined from experimentally recorded time-series.

The characterization work is an important step when studying a piezoelectric materials, it allows to link the mechanical characteristics to the electrical ones. Nevertheless for high excitation levels, significant changes in piezoelectric properties occur. They result in a performance limitations for high power transducers. A better understanding of this nonlinear behavior is needed to optimize heavy duty transducers. We chose to study a symmetrical Langevin transducer close to its resonance frequency, so under high stress and strain, and we elaborated a transducer model based on nonlinear piezoelectric constitutive equations. Simulation results fit nicely with experimental data. Moreover, introduction of nonlinear terms leads to a new explanation of the dissipated power in heavy duty transducers and correlation between model and experiments gives an estimation of the nonlinear parameters.

Local control of an acoustic projector or boundary can, in principal, be accomplished using large area locally-controlled actuators with an imbedded or intimately bonded sensor arrays. However in practice the marriage of an actuator and sensor array is not straightforward. In a basic research study, this paper considers the design and performance of a generic smart actuator for underwater acoustic applications. Both surface pressure and surface velocity sensing are included. Models are presented for understanding the importance of some of the mechanisms and construction issues involved, and for predicting the resulting system transfer functions. The predictions are compared with freefield experimental results.

Piezoelectric solid-state actuators continue to gain in technical and economic significance for a great variety of applications such as quick fine-positioning tasks, control of structural stability and active noise and vibration control due to the high driving forces, short reaction times and compact construction of these actuators. Microelectronics and signal processing must be combined intelligently to form `smart actuators' in order to do justice to the growing demand for precision, miniaturization, efficiency and cost. Energy transducers with piezoelectric PZT ceramics (PZT: lead-zirconate-titanate) simultaneously possess actuator and sensor capacities. An important requirement for the construction of smart actuators is fulfilled by separating the sensor information (charge approximately external force) from the actuator control quantities (elongation approximately electric field strength). A closed-loop control structure with digital signal processing and a voltage controlled power amplifier were developed to enable nearly load-independent linearization of the actuator's response characteristic (elongation-voltage curve) even under dynamic operating conditions by making use of the `self-sensing' effect and without using extra force or displacement sensors. The effectiveness of the developed approach for realizing smart actuators was verified and specified with the help of a computerized large-signal measurement set-up using a low-voltage piezoelectric ceramic stack as an example.

Piezoelectric materials (PZ-PT 50-50, PMN-PT 65-35) and electrostrictive materials (PMN- PT 90-10) are potential candidates for the future integrated micro-systems because of their high dielectric constant and elastic modulus. They can be used in a cantilever laminated structure for active vibration control, smart acoustic sensors and agile transducers. The first stage of the study has been made with screen printed thick films: modeling of transfer functions of sensor and actuator is made by analytical methods and experimentation of closed loop regulation is shown on a 15 mm long device. The second stage is the miniaturization of the device on silicon substrate by using sol-gel deposition, microlithography and wet etching. The modeling of a 10 times smaller device is made with data coming from experimental measurements on thin films. Expected deviations and sensitivities are calculated with the same model as above.

A piezoelectric ZnO layer is used to set thin silicon membrane into vibrations. The possibility to apply this micromechanical structure as an ultrasonic transducer is studied. High vibration modes are characterized with a considerable ultrasonic radiation. The application of the structure for ultrasonic nebulization is discussed.

This paper deals with a 2D (x-y) actuator using multimode degeneration of bending vibrations - B₂₁,B₂₁' modes - and a radial vibration - (R,1) mode-excited in a piezoelectric ring vibrator. This actuator is aimed for not so large movement such as the one of a camera lens. The operating principle and the driving methods for movements of the actuator are presented. Degeneration conditions of the modes are considered by applying F.E.M., and the construction and characteristics of a prototype actuator are shown. It was found that the 2D (x- y) actuator can be made possible using the multimode ring vibrator proposed here.

Ultrasonic motors have very interesting features as high torque at low speed and low inertia. The principle of such motors is based on a double energy conversion. This paper deals with the measurements required to characterize these conversions. Experimental results on some structures investigated in our laboratory are proposed.

A new structure of a multi-mode piezoelectric motor is proposed and uses two longitudinal actuators and a mechanical coupler. The basic principle is first presented and the corresponding modeling based on numerical tools and electromechanical circuits is performed to design a first prototype. Preliminary measurements indicates the reliability of the principle, a good agreement with predictions and interesting motor performances.

A variational model of the nonlinear response of a magnetostrictive actuator to applied magnetic fields and loads, taking into account the complex behavior of the underlying domain patterns, is discussed. Magnetostriction curves for a Terfenol-D-like material in a 2D geometry are calculated exactly, and compared with experimental measurements for Terfenol- D, suggesting an explanation for the observed behavior.

Aim of the present paper is to analyze and compare two different models used to study the axial vibration problem of a beam structure actuated by piezoelectric layers bonded to it. Crawley and de Luis [4] have recently set up a distributed dynamic model for both the axial and the flexural dynamic of an actuaded beam structure. Rogers has explored the possibility of describing the dynamic interaction between piezoelectric actuators and a beam structure by means ofa lumped model [5]. In the first section of this paper a completely lumped parameters model will be presented and discussed; the results wiil be compared in the second section with the ones obtained for a distributed model.

This paper presents the methodology to design and optimize a feasibility demonstrator for low- frequency active vibration control of a composite plate. An original approach has been achieved and several problems due to the behavior of the piezoceramic explained and solved.

The use of passive and active damping techniques which employ viscoelastic materials as the damping medium is discussed. The importance of identifying the correct material properties is described and certain problems which can occur at high frequencies are mentioned. A comparison is drawn between active damping (AD) and active constrained layer damping (ACLD) using PZTs as the actuators and it is shown that for the examples studied, ACLD offers advantages. The paper finishes with comments on the future directions for damping studies.

The forced vibration of a cylindrical shell is controlled using the distributed piezoelectric actuators and hybrid control method. The shell is constructed from a polyester film in the middle surface and two piezoelectric films, one on each side. The electrodes on the surfaces of the piezoelectric films are divided into several parts and two parts on the films are used as actuators. The shell is vertically mounted on a vibration table and excited by the horizontal motion of the table. The hybrid control method which is a combination of (mu) -synthesis control and disturbance cancellation method is used. Simulation and experiment were carried out and the results show that the hybrid control is more effective than each individual control method.

A smart solution to vibration suppression in form measuring machines is presented in which the machine's vibrations are counteracted actively. For this purpose, the machine was equipped with a sensing system, an active interface, and a special controller. This new concept has been successfully tested on a real form measuring machine.

Multi-modal vibration control of laminated composite plates using collocated piezoelectric sensor/actuator is analyzed theoretically and verified experimentally for various fiber orientations. The modal damping (2(zetz) (omega) ) is chosen as a performance index rather than the damping ratio ((zetz) ) for the vibration suppression in the structure. The active modal dampings of the first bending and the first torsional modes are measured experimentally and are in good agreement with those of finite element analysis.

By including piezo-materials into a light structure, it is possible to convert a part of its vibrational energy into electrical energy. When this electrical energy is addressed to a dissipative impedance, a damping effect is obtained. The achievable performances for various kinds of dissipative impedances are derived from modeling results. It is shown how the used dissipative impedance acts on the structure (mechanical equivalence) and how the obtained performances are related to a non-dimensional coupling factor. Finally numerical and experimental results from a case study are presented.

A method to increase the usable bandwidth of shape memory alloy (SMA) actuators for structural control is investigated. Because the change in material properties exploited in SMA components requires significant temperature variation, usually achieved through resistive heating, the response time of SMA actuators is ultimately limited by heat transfer in many applications. Typically, very rapid heating can be achieved but the time needed for cooling is long compared to the vibratory period of a mechanical or civil structure. By using several actuators in parallel and energizing subsets of these during successive cycles of structural motion, an effective bandwidth can be achieved that is greater than the bandwidth possible with a single actuator. This is demonstrated here for an active structural system comprised of SMA wires embedded in the outer laminae of a composite beam specimen. The beam was mounted as a cantilever and its first and second modes of vibration were excited by energizing the embedded wires.

During the last five years, the Dept. of Aeronautical Engineering of the University of Naples, has carried out a lot of work, especially on the experimental side, focused on assessing the feasibility of an active vibration and noise control approach, based on the use of piezoceramic actuators and sensors bonded to different structural elements. This paper concerns an application of this technique relative to a partially curved stiff frame of a medium civil transport jet aircraft. The general procedure, as previously assessed on different test articles, requires as first step, the dynamic characterization of the test article, to best point out the target of control procedure in terms of deformed shapes relative to the frequency of most interest. The use of PZT piezoactuators to be bonded on the structure guarantee at the same time high actuators forces in front of a low weight increment. The hearth of the MIMO (Multi Input Multi Output) feedforward control algorithm that is usually applied, is then represented by an ANN (Artificial Neural Network) control algorithm that use the evaluation of experimental FRF as measured by reference accelerometer, to calculate the optimum control forces to be applied to the actuators to minimize a target cost function. Experimental results provided over 32 dB of overall vibration level reduction in a single controlled mode shape, without any spillover effect.

"Design to Noise" is one of the new aspects considered during the planning phase of new aircraft, for different political, economical and enviromental reasons. In the low frequency range, active control seems to give the right answers to the needs. In propeller aircraft, active systems based on microphones-loudspeakers architectures5 have overtaken the classical methods based on the use of the Dynamic Vibration Absorbers.7 The problems of weight, cost and so on, could be solved by the application of "Smart Structures" , well summarised in many works and publications (e.g. C. Fuller6). Further work is being carried out at CIRA, on the use of piezoceramic devices as vibration actuators inside system architectures based on the approach known as Acousto Structural Active Control ( ASAC9'10). Recently, the attention of the aeronautical research world has been directed towards helicopters, where the acoustic problems are greater with respect to aeroplanes: extremely low frequencies involved, little noise insulation, etc. . . In addition, the inherent structural demands present some peculiarities, such as the use of large, flexible, composite elements, etc. .

The application of piezoceramics/CFRP composites for active control of aerospace structures was investigated in a laboratory scale. Exemplary results are presented for active vibration damping of CFRP plates with integrated PZT sensors and actuators as well as for shape control of an antenna reflector shell using piezoelements.

In this paper, we describe a nonlinear constitutive relation for magnetostrictive materials that includes coupling between temperature, applied loads, and magnetic field strengths. The model is used to predict the magnetic field requirements for actuating a control flap to reduce the vibrational loads in a rotorcraft system. This prediction is based on the force/displacement requirements presently available in the literature for a particular flap. Results indicate that reasonable changes in the ambient temperature and centrifugal forces generated by the rotating blade strongly influence magnetic field requirements.

This paper describes the achievement of active control headset protector using piezoceramic actuators leading to a noise attenuation of about 20 dB within a 1 kHz frequency span located at around 1 to 2 kHz. To this end, several types of piezoceramic transducers or actuators have been designed and tested. They are based on flexural modes of bimorphs constituted by a thin piezoelectric ceramic disk cemented on a metallic plate. The main problems encountered are the spurious frequency regenerations which mask the noise reduction in the expected frequency range. Thus only a few of them meet the above specifications and can be used for reducing the noise inside the headset protector.

An active system which improves the absorbent properties of a porous material sample in free field is presented. The method, which is based on the `(lambda) /4 resonance absorber' principle, associated active and passive means: a pressure minimization is achieved at the rear face of a porous layer to realize an impedance matching between its surface and the acoustic incident waves. The performances of a system including a single secondary loudspeaker, then a 3 X 3 array, are presented under normal and oblique incidence, for low frequencies under 1000 Hz.

Freeform fabrication is a family of techniques for preparing solid objects from a 3D computer- based design. The best known method is stereolithography. To date, freedom fabrication has been mainly applied to making prototypes and molds. Similar techniques can be applied to make functional parts of a range materials, including metals and ceramics as well as polymers. In collaboration with Advanced Ceramics Research Corp. of Tucson, Arizona, we have been developing a reactive extrusion method where a part is built up by extrusion of a material stream through a fine needle. A curing reaction at the deposition site allows solid components to be formed. This approach can be readily modified to deposit several materials in the same part and hence to fabricate intelligent materials containing embedded sensors and actuators. This paper describes the application of this method to an epoxy part containing an optical fiber sensor and the response of embedded polyvinylidenefluoride piezoelectric films.

Recently material processing with intiligency has been interested. Self-formation and alignment of quatum dots structure on semiconductor surface are a typical example. In this case no lithgraphic technique which is conventionally used for fabricating such a ultra fine structure is necessary. Another typical intelligent material processing is atomic layer manipulation with self-limiting process in which exact one monolayer layer-by-layer stacking or etching is automatically achieved. Atomic layer manipulation - layer-by-layer addition (Atomic layer epitaxy) and/or subtraction (Atomic layer etching) of atomic layer of a crystal - is a promising technology for future nano-device fabrication. In atomic layer manipulation, a source gas or an etching gas is alternatively fed into a reactor and self-limiting mechanism is realized. In self-limiting mechanism, source gas or etchantrecognizes automaticallyan one molecularlayer addition or subtraction of crystal and the growth or etching is automatically stopped just after one molecular layer addition or subtraction of the crystal.

The research project on Nano-Space Laboratory and related topics are reviewed. This project has been funded by the Special Coordination Funds for Promoting Science and Technology since 1994. The project is classified into three major topics: (1) materials development by atom lab, (2) materials development by molecular lab and (3) development of theory and basic technology for nano-space research. The paper describes progress of the research with emphasis placed especially on new process technologies.

Gas cluster ion beam techniques have been developed for nanoscale surface processing. Bombarding process fundamentals are distinctly different than those produced by conventional monomer ion irradiation. The unique characteristics of gas cluster ion bombardment are low energy and high current effects. Multiple collision during the bombardment solid surface produces complicate nonlinear effects. Very shallow ion implantation, low damage and high rate lateral sputtering and low temperature thin film formation are suggested application fields and have been experimentally demonstrated.

The low energy cluster beam deposition technique (LECBD) is used to produce nanostructured materials with original structures and properties. In this technique, clusters do not fragment upon impact on the substrate leading to the formation of granular films by nearly random stacking of incident clusters. Both nanostructured films and films of clusters embedded in various matrices are produced using this technique. The production and deposition of controlled size distributions of free clusters are briefly described as well as the specific nucleation and growth process characteristic of the LECBD. In the second part of the paper are presented some characteristic examples of novel materials prepared by this technique. The formation and properties of films of covalent materials (C, Si) and metallic materials (Fe, Co, Ni) are presented to emphasize the memory effect of the free cluster structure in the first case and the effect of the nanocrystalline film structure through the magnetic properties in the second case.

The design and testing of a new two-temperature metal vapor source for ionized cluster beam (ICB) method are described. The vaporized materials (Ag, atoms and clusters) from a crucible with vapor superheating is partially ionized by electrons at the crucible exit where the vapor has its highest density then accelerated in electric field (5 divided by 10 keV) and deposited on substrate of HTSC Y-Ba-Cu-O films. Very thin (100 divided by 200 nm) metal films with high density and low-resistance contacts Ag/Y-Ba-Cu-O (10^-5 divided by 10^-8 Ohm(DOT)cm²) were fabricated by ICB. The surface of the films was analyzed by SEM (SE, BSE) with computer analyzer. The application of two-temperature sources in technologies allows one to produce atomic or cluster beams, control the gas dynamic flow and product high-quality metal thin films as a result.

We have investigated the electronic structures of GaAs/Al(Ga)As and GaAs/AlAs quantum wells by resonance effects of second-harmonic generation. Second-harmonic generation signals manifest themselves in two-photon resonance with the confined 1S and/or 2P excitons in GaAs/Al(Ga)As and ZnSe/ZnS quantum wells. The assignment of the resonance is directly determined from comparison to the results of one-photon and two-photon absorption data. From the energy splitting of the 1S and 2P exciton levels, the exciton binding energies can be determined. There is a significant increase in the binding energy as compared to that in bulk materials. This increase is caused by the exciton confinement effect.

Numerous GaAs epitaxial microcrystals were fabricated on a sulfur-terminated GaAs substrate by sequentially supplying Ga and As molecular beam. The process consists of forming Ga droplets on the inert surface and reacting the droplets with As to produce GaAs microcrystals. This method termed droplet epitaxy is thought to be a promising growth method for fabricating the GaAs quantum dot structure, especially coupled quantum dot structure.

Formations of organic-inorganic hetero nanostructure consisting copperphthalocyanine, C₆₀, TiO_x and SiO₂, have been reported, and Basic information on the formation of hetero nanostructures by vacuum thin film technology was discussed. Optoelectronic functions in organic-inorganic hetero nanosystems have been demonstrated and discussed from the viewpoints of carrier generation at the interface, size effects, the difference of dielectric constance between organic and inorganic solids, and molecular orientation.

Modern approaches to the growth of high quality gallium nitride (GaN) thin films have focused on the use of organometallic vapor phase epitaxy (OMVPE). One of the keys to obtain the high quality thin film was the use of a thin buffer layer between the sapphire substrate and the growth film. Thin films of GaN were successfully prepared by our atmospheric pressure OMVPE system using GaN buffer layer over basal plane (0001) sapphire substrates. The present study will discuss the role of buffer and the influence of the temperature and ammonia/trimethylgallium (NH3/TMG) mass flow ratio in controlling morphology of GaN thin films. Normarski differential interference contrast optical microscopy and scanning electron microscopy reveal the surface and cross-section morphologies of different growth conditions. To the best of our knowledge the `volcanic cone-like' hillock structure describe here is the first reported the morphology for single crystal GaN thin films.

We propose a new systematical method to control Schottky barrier heights of metal/semiconductor interfaces by controlling the density of the interface electronic states and the number of charges in the states. The density of interface states is controlled by changing the density of surface electronic states, which is controlled by hydrogenation. We apply an establishing hydrogen termination technique for the hydrogenation using a chemical solution, pH controlled buffered HF or hot water. The density of interface charges is changeable by controlling a metal work function. When the density of interface states is completely hydrogenated, the barrier height is determined simply by the difference between a work function of a metal (phi) _m and an electron affinity of a semiconductor (chi) _s. In such an interface with zero density of interface states, an Ohmic contact with a zero barrier height is formed when we select a metal with (phi) _m < (chi) _s. We have already demonstrated controlling Schottky and Ohmic properties by changing the hydrogenation on silicon carbide (0001) surfaces.

A new concept `Frontier Ceramics' is proposed to proceed a new research project on advanced ceramics. The key lies in understanding of 2D structure such as boundaries or interfaces. The research project is to tailor the ceramic interface through controlling the structure and composition at interface with novel processing techniques to achieve the desired properties. Establishing an advanced model for the interface is certainly the fundamental step in this research.

The use of sol-gel technique to fabricate functionally graded ceramic matrix composites reinforced with woven fibers is illustrated with composites made by alternating dielectric and conducting layers (microwave absorbent) or by alternating materials that have high hardness and good corrosion resistance. Emphasis on the preparation of multiscale reinforced composites is given according to the idea of biomimetic materials.

The chemical potentials of electrons (holes), oxide ions and cations have been analyzed to clarify the mass transfer across/along grain boundaries. We have adopted two ways of (1) examining the mass transfer in grain boundaries in an analogous way to bulk phenomena and of (2) examining the chemical potential properties intrinsic to grain boundaries. For the first purpose, interesting bulk phenomena have been examined and analogous phenomena in grain boundaries are discussed in terms of a similar diffusion mechanism. For the second purpose, the non-equilibrium nature in grain boundaries are focused.

Some multi-component photorefractive crystals exhibit wide variations in their properties associated with the nonstoichiometry of the constituent cations. In order to grow single crystals with high quality and high homogeneity under nonstoichiometry control, a double crucible Czochralski method has been developed. In this method, the melt was divided into two parts by a double structure (two chamber system) crucible. The crystal was grown from the inner melt, and a powder with the same composition as the growing crystal was supplied to the outer melt. The powder was supplied continuously and smoothly at the rate of weight increase of the growing crystal. This rate was automatically controlled to match the weight increase of the growing crystals as monitored by a load cell. As an example, LiNbO₃ single crystals with a composition close to stoichiometric were grown, and their photorefractive properties were compared with those of Nb-rich congruent LiNbO₃ crystal. As the result, it turned out that the stoichiometric LN crystal exhibited higher efficiency and faster responsivity than the congruent crystal.

An example of structural control of organic thin films by self-organization is described. Equally spaced parallel atomic step arrays exist on polished sapphire (1012) surface. Dibenzo [b, t] phthalocyaninato-Zn (II) (ZnDBPc) molecules deposited by UHV molecular- beam deposition on this surface stack themselves to form columnar crystal grains. Since the direction of these columns is parallel to the atomic step direction, thin films of ZnDBPc grown on the sapphire (1012) surfaces show unidirectional in-plane ordering over the entire substrate. The direction and spacing of the parallel atomic step arrays are directly related to the misorientation direction and angle of the polished surface from the exact (1012) surface. Therefore the ordering direction of the ZnDBPc thin film has no relation to the crystallographic axes of the sapphire, which is totally unlike ordinary epitaxial growth. Since the step spacings can be controlled over a wide range, we can expect to be able to improve the ordering by adjusting the step spacings to the lattice spacing of organic crystals.

In a transmission electron microscope, we have shown that an amorphous boron filament can be obtained by Vapor-Liquid-Solid growth under intense electron irradiation (current density > 100 A/cm²) on an amorphous Boron Nitride film deposited a few-nm gold as agent. The grown filaments have gold particles on the tops and the diameter were from 10 to 100 nm. Detailed analysis of Electron Energy-Loss Spectrum of the amorphous boron was carried out. We also dynamically observed shrinking of filaments by evaporation of boron through gold particles. As a special case, boron-rich tubules of several hundreds nm diameters were also formed.

A survey is given of the modification in aerosol pyrolysis procedure for decreasing the particles size up to 10 nm adding the inert component (NaCl, NaCl + BaB₂O₄) to of the starting precursor of barium, iron nitrate and citrate solutions and demonstrate the facility of this technique in the synthesis of MeFe_2y-2xCo_xTi_xO₁₉(x equals 0 - 0.8; y equals 5.6 - 6.0; Me equals Ba, Sr) small particles.

We proposed a particles assembling method to create intelligent and multi-functional materials. The arrangement of particles on substrates was studied as one of the important techniques for this approach. The arranging process is as follows. Electrified patterns were drawn on dielectric calcium titanate (CaTiO₃) substrates with electron beam scanning. The substrates were dipped in a solvent where silica (SiO₂) particles of 5.1 micrometers (phi) were dispersed. The particles were attracted to the electrified patterns by the electrostatic force, and were arranged along the electrified patterns. In this paper, undrawn substrates were used to know how many particles adhered on the unelectrified part, and then, arranging experiments using drawn substrates were carried out under various conditions to confirm the above process. We also discussed on the basic aspects of the arrangement, such as attraction force, motion of particles in the solvent, etc.

Effects of the interface states at the grain boundaries on the applied voltage dependence of the double Schottky barrier (DSB) are theoretically discussed. Based on the simplified models of rectangular density distributions for the interface states, effects of the energy level, density of states, and the distribution width of the interface states are quantitatively calculated. The I-V characteristics of DSB's are also calculated and the nonlinear I-V relations are discussed. The nonlinear exponent (alpha) of the I-V relation was found to be determined mainly by the barrier height and the total charge of the interface states. The observed ICTS spectra and other electric properties of ZnO varistors and PTC thermistors are discussed on the basis of the above DSB model.

This paper suggests how two inverse problems can be solved using topology optimization methods. The first problem consists of designing materials with optimal or special properties such as maximum stiffness to weight ratios or negative Poisson's ratio materials. The second problem consists of designing optimal compliant micromechanism for use in MicroElectroMechanical Systems. The proposed material microstructures and compliant micromechanisms have been manufactured using micromachining techniques and they show the expected behavior in tests.

For given operational differential equations of first or second order, we find dynamical controllers such that the resulting coupled system is exponentially stable with a prescribed exponential decay rate. An application to the stabilization of plate vibrations with distributed piezoelectric actuators is described.

Many piezo actuators can be used without increasing costs and weights of corresponding control system with common control command. Piezo actuator configurations which maximizes degrees of controllability are obtained using genetic algorithms, general optimizers. Optimal placement of piezo actuators is determined for a cantilevered plate, and it is observed that actuator pattern is closely related to the phase of modal control force of each actuator.

We propose to adapt the asymptotic model of plate developed by Ciarlet to take into account specific effects as to the behavior of a piezoelectric device. Then we show how to distribute them in the thickness of a stratified composite structure, so as to detect or activate its strains optimal manner.

The dynamic behavior of piezoelectric actuators bonded on structures are completely different from its static behavior. The strong interaction between actuators and host structures delivers the response of actuators and associated power supply to be closely dependent on the dynamic state as well as the configuration of the host structures. The paper presents a new electromechanical dynamic model of a pair of actuators featuring the combination of an in- plane longitudinal wave induced by the piezoelectricity and transverse vibration concordant with the bending vibration of the actuator-bonded beam. The analytical results display that both kinds of movement of piezoelectric actuator are coupled with each other and deeply involved into the bending vibration of the beam. Moreover, its in-plane displacement and velocity response to the exciting voltage imposed across the actuators are affected not only by the resonant frequency of a bending vibrating of the beam, but also by the resonant frequency of a longitudinal wave of the piezoelectric actuator and the virtual eigen frequency of longitudinal wave of the actuator which is imaged to have the same length as the beam. The final results show that the electrical admittance of the actuator is contributed by a static, dynamic capacity of the actuator and also has the dedication of both longitudinal wave and transverse vibration coupled with the bending vibrating of the beam.