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采用考虑纤维束相互挤压的纤维束截面八边形单胞模型,引入周期性边界条件,对三维编织复合材料的渐进损伤过程进行数值模拟,并预测了材料的拉伸强度。通过在应变能密度函数中引入损伤状态变量,建立了含损伤材料的刚度矩阵,运用基于不同失效模式下损伤状态变量的刚度渐进折减法表征材料积分点损伤,通过数值结果与试验结果的对比,分析了Hashin和Tsai-Wu两种准则作为判定纤维束起始损伤的适用性。分析表明:基于引入不同失效模式的Tsai-Wu准则的数值模拟和试验结果吻合良好;Hashin准则不适合作为编织纤维束的损伤判据;不同编织角材料的失效机制不同。
By adopting the octagonal unit cell model of fiber bundle cross-section, the periodic boundary conditions are introduced to simulate the progressive damage of three-dimensional braided composites and predict the tensile strength of the material. By introducing the damage state variables into the strain energy density function, the stiffness matrix of the material with damage is established, and the material integral point damage is characterized by the incremental stiffness reduction method based on the damage state variables under different failure modes. By comparing the numerical results with the experimental results, Hashin and Tsai-Wu criteria were analyzed as applicability to determine the initial damage of fiber bundles. The analysis shows that the numerical simulation based on the Tsai-Wu criterion with different failure modes is in good agreement with the experimental results. The Hashin criterion is not suitable for the damage criterion of braided fiber bundles. The failure mechanisms of different braid angle materials are different.