纱线规格对3D机织复合材料拉伸性能的影响

Effect of yarn size on tensile properties of 3Dwoven composites

为研究纬纱规格对3D层-层斜纹机织复合材料细观结构和力学行为的影响,开展了系统的实验研究。采用光学显微镜观察了不同纬纱规格复合材料的细观纱线结构变化。开展了不同纬纱规格复合材料的拉伸实验,采用数字图像相关法获得了拉伸试样的表面应变场,结合断口形状分析了复合材料的拉伸失效机制。研究表明,随纬纱规格增大,经纱卷曲率增大,经向纤维体积分数减少,经向拉伸力学性能减弱;纬纱卷曲率减小,纬向纤维体积分数增大,纬向拉伸力学性能增强。此外,3D机织复合材料拉伸应力-应变曲线表现出了明显的“台阶”效应,承载纱线的卷曲率越大,“台阶”效应越明显。

Systematic experiments were carried out to investigate the effect of weft yarn sizes on the mesoscopic structure and mechanical behavior of 3 D 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 3 D woven composite exhibits a significant“step”effect,which becomes more obvious with higher crimp rates of load-bearing yarns.