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 o pen hole for tape laminated composites is evaluated for its applicabil ity to 2D triaxial braided textile composite materials. Four different textile architectures are considered; braid angle, yam and braider si ze and percentage of longitudinal yarns varied. Tape laminates equival ent to these textile composites were also constructed for comparison. Compliance calculated using the measured normal stress distribution fr om 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 cor relations between measured and predicted compliances were stronger for the tape equivalents and at smaller braid angles, however no statisti cally significant differences between measured and predicted complianc es for textile and tape equivalents were detected. The method develope d to predict the normal stress distribution was equally effective for all materials, architectures, specimen widths and strain gage location s. 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.