针刺C/C复合材料拉伸强度及渐进失效数值预测

基于金相显微镜观测的针刺C/C复合材料细观结构，考虑材料内部纤维的真实分布，建立了针刺C/C复合材料单胞模型。采用Linde失效准则，考虑纤维渐进损伤对材料进行了刚度折减，通过引入周期性位移边界条件，对针刺C/C复合材料的拉伸破坏进行了有限元法（FEM）数值模拟，分析了单胞模型的渐进失效过程，并预测了材料的拉伸强度。开展了针刺C/C复合材料拉伸试验，采用扫描电子显微镜（SEM）观察了材料的断口形貌，数值预测结果与试验吻合良好。针刺C/C复合材料受拉伸载荷后发生准脆性断裂，拉伸应力-应变曲线呈双线性，0°无纬碳布发生纤维断裂和基体开裂破坏，90°无纬碳布出现横向基体劈裂，最终断裂发生在针刺纤维与面内无纬碳布交叉区域。

Numerical prediction of tensile strength and progressive damage of needled C/C composites

Based on the observation of microstructures of needled C/C composites, a unit cell model which considered the true distribution of the fibers was established to predict the tensile strength and progressive damage. The finite element method (FEM) simulation of the tensile failure of the composites was conducted by using the failure criterion proposed by Linde and periodic displacement boundary conditions. The damage evolution of the composites was analyzed, which was subject to the longitudinal tensile load, and the tensile strength was predicted. By doing a quasi-static tensile test, the rupture surface of needled C/C composites was observed by scanning electron microscope (SEM). The numerical prediction was in good agreement with the test results. Quasi brittle fracture occurred under tensile load, and the stress-strain curve approximately presented bilinear shape. 0° weftless plies suffered from fiber breakage and matrix cracking damage, and 90° weftless plies from matrix damage. The final fracture occurred in the regions where the in-plain fiber and the needled fiber intersected.