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2.5维机织复合材料已有较为广泛的应用,而目前对该类复合材料的破坏机理和失效原因尚未形成统一的认识。根据三维机织复合材料的拉伸试验现象,基于经纱曲面层板纬向纤维和树脂应力相等的假设,建立了2.5维机织结构复合材料纬向拉伸过程的初始屈服条件和屈服准则。通过对2.5维机织复合材料3种结构12个试件进行纬向拉伸试验及文献中的三维机织复合材料拉伸试验,与计算预测结果的对比表明本文中建立的初始屈服准则的合理性。研究表明,树脂横向裂纹是2.5维结构复合材料纬向拉伸过程初始屈服产生的直接原因;2.5维机织复合材料出现纬向拉伸屈服的条件仅和经纱曲面板内的经纱体积含量、纤维和基体的弹性模量及基体的拉伸破坏强度等因素有关,而与经纱曲面板的走向和层数无关。因为组分弹性模量不同,在纬向拉伸过程中,树脂应变高于复合材料的应变。树脂的初始横向裂纹首先发生在纤维密集处,并向富树脂区扩展;裂纹在向纤维方向扩展过程中受到纤维的阻碍而受到限制。
2.5-dimensional woven composite materials have been more widely used, but the current failure mechanism of such composite materials and failure causes have not yet formed a unified understanding. According to the tensile test of 3D woven composites, the initial yield conditions and yielding rules of the 2.5D woven composite were obtained based on the assumption that the zonal fibers and the resin stress were equal in the warp yarns. The tensile test of 12 specimens of 3 kinds of structures of 2.5-dimensional woven composite material and the three-dimensional woven composite material in the literature were carried out. Comparing with the calculated results, the initial yield criterion established in this paper is reasonable Sex. The results show that the transverse crack of the resin is the direct cause of the initial yielding of the 2.5-dimensional composite in the zonal direction. Only the warp yarns’ volume content in the warp surface of the 2.5-dimensional woven composite, And the elastic modulus of the matrix and the tensile strength of the matrix and other factors, but with warp and curved surface of the board has nothing to do with the number of layers. Because of the different elastic modulus of the components, the strain of the resin is higher than the strain of the composite during the zonal stretching. The initial transverse crack in the resin occurs first at the fiber density and expands toward the resin-rich zone; cracks are limited by the hindrance of the fibers as they propagate in the fiber direction.