Performance of Non-Crimp Fabric Composites in Shear

Abstract

Experimental results of performance of non-crimp fabric composites are presented in this paper. In order to characterize in-plane shear properties of these composites, tensile and compression tests of [±452]S specimens were carried out. Two directions of loading are considered: warp (Shear warP: SP) and weft (Shear wefT: ST). This corresponds to laminates with the following lay-up: SP = [+45/-45/+45/-45]S; ST = [-45/+45/-45/+45]S. Although both types of laminates are cut from the same plate, mechanical performance in tension is rather different: laminate cut in weft direction exhibit higher shear modulus, shear strength and shear strain at failure than samples cut in warp direction. Fractography showed that different behavior of the materials is caused by much earlier damage initiation and accumulation in SP laminates. Analysis of images obtained from optical microscopy indicated that premature failure is most likely caused by stitches that prevent free rotation of bundles (shear deformation).