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Description
2020 Carbon fiber reinforced polymer composites (CFRP) are prone to delamination damage which leads to the reduction in the mechanical performance of aerospace structures. Electrical Resistance Tomography (ERT) is a non-destructive evaluation technique that uses surface voltage measurements with electric currents injections in the material to measure electrical conductivity changes induced by damage. Accurate and efficient damage identification in CFRP composites using ERT with hardware limitations on sensor measurements requires techniques for selecting optimum sensing combinations. A novel method to select the optimal sensing configurations for ERT damage identification is proposed and demonstrated. The effectiveness of the method is verified using surrogate model based optimization for damage identification. The physical contact of embedded crack faces leads to current paths through the crack that limits the accuracy and resolution of ERT damage identification. To overcome this limitation, a new hybrid NDE technique that combines wave actuation with ERT is proposed. To enable this hybrid approach, numerical simulations of the forward problem that can predict the effect of wave actuation in a composite with delamination crack on ERT measurements are developed. Discontinuous Galerkin Spectral Element Methods were implemented for the numerical simulation of the wave propagation in laminated composites with embedded delamination. An electromechanical contact model was implemented to translate the mechanical contact to surface contact resistivity on the crack face. This was coupled with Spectral Element Methods solution for the electrical conduction problem in an CFRP laminate with delamination to compute the surface potentials as needed for ERT simulations. Numerical experiments of ERT sensing with wave actuation were investigated for different sensing configurations. The developed methods provided an efficient numerical simulation tool for the ERT forward problem. The results show that the combined wave actuation with current injection can increase the sensitivity in ERT damage detection.
