Normal Stress Distribution of Notched 2D Triaxial Braided Textile Composites and Tape Equivalents under Tension

A theory developed to predict the normal stress distribution near an open hole for tape laminated composites is evaluated for its applicability to 2D triaxial braided textile composite materials. Four different textile architectures are considered; braid angle, yarn and braider size and percentage of longitudinal yarns varied. Tape laminates equivalent to these textile composites were also constructed for comparison. Compliance calculated using the measured normal stress distribution from notched coupons with three different open hole sizes were compared to compliance calculated from the normal stress distribution predicted using the extended isotropic solution [1]. Results indicated that correlations between measured and predicted compliances were stronger for the tape equivalents and at smaller braid angles, however no statistically significant differences between measured and predicted compliances for textile and tape equivalents were detected. The method developed to predict the normal stress distribution was equally effective for all materials, architectures, specimen widths and strain gage locations. Our results validate the use of approximate theory to predict near-notch stress distribution in 2D braided textiles tested in this study and suggest that the textiles behave as orthotropic material.