Multi-level nondestructive analysis of joint-debond effects in sandwich composite structure

This paper presents a non-destructive analysis of joint-debond effects on propagating guided wave modes under variable ambient temperature conditions and proposal of an online monitoring strategy for identification of single as well as multiple joint-debond regions in a sandwich composite structure (SCS). A semi-analytical analysis of guided wave dispersion in a SCS was carried out to identify different wave modes within the operating frequency range. An extensive analysis of core-core joint-debond effects on the guided wave modes under variable temperature conditions was studied by performing experimental investigations and validated finite element simulations. The analysis results showed that the presence of joint-debond at the core-core interface significantly increases the wave mode amplitudes and the increase in ambient temperature further increases the amplitude difference between the bonded and debonded-influenced signals. An online monitoring strategy is proposed to effectively identify the hidden joint-debonds in SCS based on the extracted differential features of debond effects in the wave mode amplitudes of the sensor signals.