Energy-absorption properties of braided composite rods

Braiding has been attracting a great deal of attention as a technique for manufacturing preforms for composite materials. It has been developed as an integrated braiding technique which permits the fabrication of near-net-shaped preforms for 3-dimensional composite materials with reinforcing fibers oriented continuously. A braided rod is a simple unit of a 3-dimensional near-net-shaped composite. From this point of view, crushing tests have been performed in order to evaluate the braided rods. The specific energy absorption (Es) values of this material were higher than that of glass-cloth/epoxy tube. In this paper, we have tried to apply a flexible interphase concept to braided rods in order to obtain superior energy absorption properties. Braided composite rods with a flexible interphase also showed the characteristic crushing mode called progressive crushing. Consequently, the specific energy absorption of the rod with a flexible interphase was 30% higher than that of a composite without a flexible interphase. The fracture mechanisms of both materials are discussed with reference to microscope observations of crushed samples.