纤维束波动效应对平纹编织复合材料损伤行为的影响

平纹编织复合材料中纤维束波动效应会引起随动材料主方向变化及面外剪切应力集中，为了研究其对平纹编织复合材料力学性能及损伤行为的影响，提出改进的像素法细观有限元单胞模型。模型根据纤维束波动曲线定义了材料主方向的变化，采用Hashin准则模拟纤维束的损伤起始，并引入剪切修正因子考虑面外剪切应力对面内拉伸损伤的影响。模型可以预测平纹编织复合材料的面内拉伸强度和损伤演化过程，结果表明:纤维束材料主方向波动会引起平纹编织复合材料面内拉伸强度下降；面外剪切应力集中是导致复合材料最终失效的主要原因，且随着剪切修正因子增大，复合材料面内拉伸强度显著降低；纤维束材料主方向波动和面外剪切应力集中均对平纹编织复合材料的损伤行为和破坏机理产生了影响，需要在数值分析中对其进行准确描述。 

Damage behavior of plain woven composites considering undulation effect of fiber bundles

The undulation effect of fiber bundles on plain weave composites causes the variety of slave material principal direction and the concentration of out-of-plane shear stress.A meso-scale finite model based on the improved voxel meshes for a unit cell was utilized to explore the influence on the mechanical properties and damage behavior for plain weave composites.In the model,the variety of slave material principal direction was defined according to the undulated curve of fiber bundles,and a shear correction factor was introduced into Hashin criterion which was used to predict the initial damage of fiber bundles to consider the effect of out-of-plane shear stress on in-plane tensile damage.The model can accurately simulate the in-plane tensile strength and damage process.The results indicate that the undulation of slave material principle direction gives rise to the decline of in-plane tensile strength for plain weave composite.The concentration of out-of-plane shear stress is the main factor leading to the failure of composites,and reduces the tensile strength significantly with the increase of shear correction factor.In addition,both the two factors have affected the damage behavior and failure mechanism of plain weave composites,which need to be expressed accurately in numerical analysis.