Failure of Braided Carbon/Epoxy Composites under Biaxial Compression

Abstract

Although textile composites have been studied for some time, experimental stiffness and failure data have been limited. This study presents the experimental results from compressive tests involving triaxially braided fibrous composite cylindrical specimens. The specimens consisted of four different braid architectures, and were loaded both uniaxially and biaxially. Predicting the failure of textile composites has received relatively little attention in the literature in comparison to the work that has been done on predicting stiffness. A maximum fiber-direction strain criterion was applied to the four architectures considered in this study, and was found to correlate failure of the braided specimens as well as it has in the past for laminated materials. The failure strains of the braided specimen's axial yarns were observed to be quite sensitive to small undulations resulting from the braiding process, and fell between -0.5% and-1.4%. The failure strains of the braid yarns, with relatively large undulation, were less sensitive to undulation changes within the architecture or even between the architectures, and fell between-0.3% and -0.5%.