Transverse impact response and residual flexure characteristics of braided composite tubes: Effect of stacking sequence

The study aims to understand the effect of stacking sequence on the impact response and residual flexure characteristics of braided composite tube by combination of low-velocity impact, fracture observation and acoustic emission monitoring. Two stacking sequence configurations of braided tube in terms of [(I)60/(O)40] and [(I)40/(O)60] were designed and their low-velocity impact response and damage behavior were examined. Uniform structures namely [(I)40/(O)40] and [(I)60/(O)60] were also employed as reference specimens. The quasi-static bending performances of intact and impacted tubes were further compared to evaluate the influence of impact damage on residual performance. The results show that failure mode of impacted tubes strongly depends on braided structure of outer ply, of which large braiding angle (60 degrees) leads to the formation of bottom delamination and degradation of structural integrity. The comparative experiments indicate that [(I)60/(O)40] tube improves flexure after impact performance with respect to specific energy absorption by 45.98% over [(I)40/(O)60] counterpart because of absence of bottom delamination. Thus, structure design of braided composite consisting of intra-ply structure and stacking sequence would be an economically feasible method to improve the transverse mechanical performance.