Transverse indentation response and residual axial compressive characteristics of metal-composites hybrid tubes by deep learning-based acoustic emission and micro-CT

This work investigated transverse indentation response and residual axial compressive characteristics of Al-CFRP hybrid tubes with different configurations. The failure mechanism and damage evolution of the hybrid tubes under transverse indentation load were investigated by acoustic emission and micro-CT technologies. To gain an insight into the damage mechanism of CFRP composites, a structural health monitoring system based on image-based acoustic emission waveform and deep learning was developed. It showed that acoustic emission response of internal damage was corresponding to the damage visualization analyses of micro-CT. The proposed damage classification model provided a reliable path for extreme damage mode recognition and damage monitoring of composite structure. Under transverse indentation load, delamination and fiber breakage were the main failure modes of H-I hybrid tube (i.e. the CFRP tube internally filled with aluminum tube). For H-II hybrid tube (i.e. the aluminum tube internally filled with CFRP tube), the interfacial delamination of Al/CFRP tended to aggravate its failure behavior. The quasi-static axial compressive properties of intact and pre-indentation tubes were further compared to evaluate the effects of indentation damage on residual crashworthiness. The transverse indentation resulted in the change of the failure mode. Compared with H-I hybrid tube, H-II hybrid tube showed more significant property degradation.