Monitoring of torsional damage of quasi-static indented carbon/aramid fiber-reinforced hybrid laminate using acoustic emission

Acoustic Emission (AE) was used to monitor the entire torsion loading process of various carbon/aramid fibre-reinforced hybrid composites with different structures and with an indentation to simulate indentation-induced damage. AE signals were recorded, and the data were used for damage characterisation. The results showed that the failure torque of the specimen without an off-axis structure decreases by more than 20% after being subjected to indentation damage, while the failure torque of the off-axis structure specimen decreases by approximately 10%. Therefore, the off-axis structure can improve the toughness of the specimen and has better performance in resisting indentation damage. It was shown that indentation damage can influence the order of occurrence of the different damage modes and can decrease the peak AE frequency seen for fibre breakage. The resulting data offer new insights to guide composite component design and their SHM when used in applications such as aerospace structures.