Model-based inverse problem for damage reconstruction in composites

Carbon-fiber reinforced polymers (CFRP) are high performance advanced materials with a growing applicability due to their extreme strength-to-weight and rigidity-to-weight efficiency ratios. One of the major concerns associated with composites is their vulnerability to impact and fatigue damage. The latters may lead to delamination, sub-surface matrix cracking, fiber-matrix debonding and fiber fracture [1], which in turn can induce severe degradation in the residual material mechanical properties, while remaining invisible from the surface. Thus, non-destructive evaluation (NDE) techniques are required to discriminate between the different failure mechanisms in composites and to guarantee their reliability. Among them, ultrasonics is currently one of the most frequently used NDE techniques that have been proven to provide effective and reliable results at relatively low cost for the purpose of identifying and quantifying damage [2].
The proposed methodology consists of three elements: An (1) experimental setup based on ultrasound-composite interactions is monitored with an immersion tank equipped with a 3D motion controller, a (2) numerical model that simulates the ultrasound-composite interactions, and a (3) model-based inverse problem is used to reconstruct the relevant damage parameters [3]. The experimental system is idealized by a mathematical model of the propagation and interactions of the ultrasonic waves with all the parts of the system until they are captured by the receiver. This mathematical approach is approximated by a semi-analytical model of the wave interactions within multilayered materials, based on the transfer matrix…

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