Mechanical Properties of Triaxially Braided Composites: Experimental and Analytical Results

Abstract

This paper investigates the unnotched tensile properties of two-dimensional (2-D) triaxial braid-reinforced composites from both an experimental and an analytical viewpoint. The materials are graphite fibers in an epoxy matrix. Three different reinforcing fiber architectures were considered. Specimens were cut from resin transfer molded composite panels made from each briad. There were considerable differences in the observed elastic constants from different size strain gage and extensometer readings. Larger strain gages gave more consistent results and correlated better with the extensometer readings. Experimental strains correlated reasonably well with analytical predictions in the longitudinal, 0°, fiber direction but not in the transverse direction. Tensile strength results were not always predictable even in reinforcing directions. Minor changes in braid geometry led to disproportionate strength variations.