Transition from folding to splaying failure of braided composite tubes subjected to axial compression hybridized by bi-axial and tri-axial laminate

The failure mode is a dominant factor of mechanical performance of braided composite tube subjected to axial compression. The failure mode was modified by tailoring stack-up sequence of composite tubes hybridized by bi/ tri-axial braided laminate. The thermal photographing and micro-CT scanning methods were employed to monitor the in-situ damage progression and post-mortem specimen, respectively. The results show that the delamination was easy to be induced at the interface nearby tri-axial braided laminate. It attributes to the combination between the crack caused by local buckling of the axial yarns and the crack caused by shear deformation of braiding yarns. By the illumination of this behavior, delamination is controlled to occur at the different position along thickness direction of braided tube by adjusting the stacking sequence of braided laminates. When delamination position transfer from the inner/outer sides to the middle of tube wall, the failure mode transfer from the progressive folding to splaying, which increase the specific energy absorption by 45.77%.