纱线规格对3D机织复合材料拉伸性能的影响

Systematic experiments were carried out to investigate the effect of weft yarn sizes on the mesoscopic structure and mechanical behavior of 3D layer-to-layer twill woven composites. Variations of the mesoscopic yarn structure of the composite with different weft yarn sizes were observed by optical microscopy. Tensile tests were carried out for the composite with different weft yarn sizes. The digital image correlation method was applied to obtain the surface strain field of the tensile specimens. The tensile failure mechanism of the composite was analyzed based on the fracture morphology. It is shown that with the increasing weft yarn size, the crimp ratio of warp yarns increases, the volume fraction of warp fibers decreases, and the warp tensile properties are weakened. However, with increasing weft yarn size, the crimp ratio of weft yarns decreases, the volume fraction of weft fibers increases, and the corresponding weft tensile properties are enhanced. Furthermore, the tensile stress-strain curve of 3D woven composite exhibits a significant "step" effect, which becomes more obvious with higher crimp rates of load-bearing yarns.