Failure behavior and crashworthiness characteristic of repaired composites-metal hybrid tubes by acoustic emission

In this study, the transverse indentation test was applied to simulate the damage caused by impact to the carbon fiber-reinforced plastics (CFRP)/Al hybrid tube, and composites patch repair technology was used to repair the hybrid tube with different damage degrees. The effects of width and ply-number of the patch on failure behavior and crashworthiness under axial load were investigated. It was concluded that the technology can effectively reduce stress concentration around the indentation and then improve compressive strength. Increasing the ply-number of the patch can mitigate the failure mode of med-length collapse of the hybrid tube and can effectively improve the crashworthiness indicators. The optimal repair strategy increased energy absorption by 54.02% and mean crushing force by 53.66%. However, the improvement of failure behavior by the ply-number is limited by patch width. Acoustic emission and infrared thermography technologies were used to further analyze the damage characteristics and damage evolution of the hybrid tubes in pre-crushing stage. It was found that the crushing form of the middle collapse tended to produce a more intense acoustic emission response and higher temperature change than that of the end crushing. In engineering practice, it provides a valuable reference for the reasonable repair of composite tubular structures and their hybrid structures.Highlights Composite repair technology is used for the repair of CFRP/Al hybrid tubes. The effects of ply-number and width of patch on repair quality are studied. The technology can effectively improve residual crashworthiness of structure. The improvement of failure behavior by ply-number is limited by patch width. The damage behavior of various crushing forms can be revealed by AE and IR.