Abstract
Problem statement: The present work carries on the use of a method based on the wavelet transform to detect internal flaws of composite materials. The objective of this work consists in working out a data processing sequence of an ultrasonic signal identifying nearly flaws in composite laminate materials and estimating their position. Approach: The use of a numerical signal processing technique, based on the Fast Wavelet Transforms was applied. Results: The method was implanted and optimized for detection and classification of delamination and porosity flaws in manufactured materials. Since the information about the signal requires a large amount of computation time and resources, a technique was used to reduce the dimensions of the sampling signals. In Non-destructive evaluation of stratified composite materials, the identification of some defect features requires more recent and advanced methods than classical techniques. Notably, in thin composite materials, the reflected NDE ultrasonic signals were overlapping. As a result, the flaws evaluation was becoming unfeasible. Many works dedicated to advanced signal processing based on time-frequency analysis had been widely used in Non-Destructive Evaluation (NDE) applications. To evaluate the nearly flaw detection of delamination and porosity enclosed in composite multilayer plate, the wavelet analysis was applied to ultrasound waveforms acquired by immersion pulse-echo technique. Conclusion: The obtained results offer some defect features relating their nature and position. The applied wavelet analysis provided excellent results for the investigated materials containing artificial delamination and porosity flaws.
Highlights
The design and analysis of composite materials being more complex and more expensive than the conventional materials, such as the steel and the aluminum, the anisotropic behaviour of these materials makes their structural analysis difficult, so the use of more sophisticated methods for their analysis is required (Med et al, 2009; Yahiaoui et al, 2009).Developing the applications of composites in the mechanical structures requires the use of the non destructive evaluation of the mechanical behaviour of these materials
The field of the multilayer materials evaluation aims to strengthen the diagnosis in matter of researching defects especially the fibres basis composites of carbon or glass and epoxy in particular, the distinction between micro-cavity and enriched areas with resin as well as the position of the echo signal resulting from the cavity near the first reflected echo signal
The training set was comprised of scanned signals from both damaged and undamaged samples using stratified composite materials
Summary
Developing the applications of composites in the mechanical structures requires the use of the non destructive evaluation of the mechanical behaviour of these materials. For the evaluation of reinforced fibre composites, emerges the problem of a great acoustic attenuation of the measuring signals. This problem raises a notorious difficulty in the applications of non destructive ultrasonic evaluating methods. As a result, it needs the use of different approaches of signal processing to analyse the signal of the propagating wave in the probed material. The basic algorithm used is based on the DWT to analyse the measurement errors of the size and to locate the position of the artificial defects in the tested composite materials
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