Crush-failure modes of 2D triaxially braided hybrid composite tubes

Six different hybrid types of two-dimensional (2D) triaxially braided composite tubes containing Kevlar and carbon fiber were designed to study their crush-failure modes and specific energy-absorption capabilities. Quasi-static axial compression a-as employed to investigate the effect of hybrid type on the crush-failure characteristics and energy-absorption mechanisms. The crushing appearance and failure modes in the crushing zone were examined by optical microscopy. It was observed from the crushing tests that the hybrid types of 2D triaxially braided composite tubes significantly influenced their crush-failure modes and crush-energy absorption. There were three different crush-failure modes occurring in the crush tests of the six different hybrid composite tubes, a splaying mode for tubes with carbon braiding yam, a folding mode for tubes with Kevlar braiding yarn, and a spiral-curling mode for tubes with both carbon and Kea lar braiding yarns. Among those six different composite tubes, that braided with all carbon fibers exhibited the highest crush energy absorption. By contrast that braided with all Kevlar fibers showed the lowest crush energy absorption, but had the best post-crush integrity. (C) 1999 Elsevier Science Ltd. All rights reserved.