Abstract
This is a novel investigation on the possibility of detecting barely visible impact damage (BVID) in composite materials by whisking across the surface via tactile whisker sensors that resemble rats’ whiskers. A series of drop tower low-velocity impact tests were performed on quasi-isotropic composite plates. The plates were made from unidirectional T800 carbon/MTM49-3 epoxy prepregs with the stacking sequence of [45/0/90/−45]4S. Investigating the specimens’ surface by the naked eye does not reveal any significant damage, rather than a small dent on the surface, with no tangible difference in the different impact energy levels. Ultrasonic C-scan observations showed the existence of BVID in all the impact energy levels, with an increasing trend in the damage size by increasing the impact energy level. The collected data from whisker sensors were analyzed using the support vector machine classifier, based on their vibrational properties, to identify the impacted region and classify the impact severity. It was observed that after training for 13 whisker contacts, the BVID severity can be classified with an accuracy of 100%. This is offering a new BVID detection technique, with a high potential for automation and high reliability that can be used as an alternative or combined with available inspection systems.
Highlights
The demand for composite laminated materials has increased significantly over the last decade
Classifiers based on Support Vector Machine (SVM) have few free parameters requiring tuning, are simple to implement, and are trained through optimization of a convex quadratic cost function, which ensures the uniqueness of the SVM solution [36]
This study investigated the feasibility of using whiskers for damage detection in laminated composite materials
Summary
The demand for composite laminated materials has increased significantly over the last decade. The application of such materials was limited to the aerospace industry. The key advantage of such materials is their high strength to weight ratio making them ideal for use as lightweight and high load bearing structural components. Poor out-ofplane properties, low damage tolerance and low delamination resistance have limited their application as primary loading components [1]. Impact damage leads to delamination (separation of plies), matrix cracking and fibre breakage [2]. This degrades both strength and stiffness reducing load bearing capacity of the composite laminate structure [3,4,5]. If the introduction of the damage is undetected, premature and catastrophic structural failures could be expected
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