The use of composite materials in aircraft manufacturing is increasing, driven by the need for reduced weight and improved fuel efficiency. This trend extends to military aircraft, as defence manufacturers and suppliers seek to minimise operating costs. However, these composites are susceptible to various defects, which require the use of advanced Non-Destructive Testing (NDT) techniques for their detection and evaluation. Phased Array Ultrasonic Testing (PAUT) is such an NDT technique that provides precise defect characterisation, including delaminations, cracks, voids, and porosity. Active Thermography (AT) is an alternative NDT technique that is emerging as a non-contact and full-field technique for identifying such defects. PAUT and AT are complementary techniques, and a synergistic approach that combines their capabilities promises enhanced aircraft safety and composite structure reliability. This paper presents research findings using PAUT equipment and active infrared thermography for identifying and evaluating defects in composites. The presented combined approach is expected to improve aircraft safety and composite structure reliability in aerospace applications.
Non-destructive testing applications are one of the most crucial steps in maintaining aviation activities in a profitable and timely manner. Infrared thermography (IRT) is a functional technique that uses the thermal radiation/temperature relationship on the inspected structure to ensure efficient detection, in particular when the defect is on a surface or near the surface. Ultrasonic (UT) inspection is an alternative technique that uses the propagation of ultrasound waves into the inspected material for defect detection. While IRT suffers from detectability problems with the increasing structure thickness, UT has inspection limitations on the surface or near-surface area according to applied frequency. Overcoming these limitations of individual methods with the synergistic effect of the fusion approach might provide more precise and apparent marks for defect detection. In this study, decision-level fusion has been applied using the maximum fusion rule to combine unimodal inspection data and compare. Impact-defected Carbon Fiber Reinforced Polymer (CFRP) composite structures have been chosen to represent aerospace structures. The results show the proposed fusion approach is promising in terms of identifying defect location, size and depth to inform further stages such as repair.
Composite materials have extensively been used in the aerospace industry. There are several inspection methods to ensure the safety of these composites; pulse thermography (PT) is one of the most promising ones. Both reflection and transmission modes of PT could be applied. However, few studies reveal the advantages and disadvantages of these two modes. This paper presents a quantitative comparison of pulsed thermal imaging in two modes of reflection and gradual heat transfer in carbon fibres. Experimental work was conducted on carbon fibre-reinforced plastic (CFRP) samples with different thicknesses and thermal images were recorded in both modes. Thermal images were further processed using statistical analysis and machine learning algorithms. Comparing the results from both modes, there is a marked improvement in the accuracy when the reflection mode is employed.
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