2D-SiC/SiC复合材料拉伸加卸载行为

Tensile loading/unloading stress-strain behavior of 2D-SiC/SiC composites

为了研究国产2D-SiC/SiC复合材料的拉伸损伤行为以及低周循环载荷作用下的力学性能,通过试验和建立加卸载细观力学模型,对其拉伸加卸载行为进行了探讨。建立了单向连续纤维增强陶瓷基复合材料加卸载细观力学模型,得到了初始加载、卸载和重新加载时的应力-应变关系;利用断裂统计方法得到了基体裂纹数随应力变化的关系和复合材料失效判断条件。经过应力转化,将该模型应用于国产二维编织SiC/SiC复合材料。对单向加载试件,采用正交试验方法和最小二乘法得到基体Weibull模量和界面剪切阻力,通过控制材料失效强度与试验结果一致,得到纤维Weibull模量。由上述参数确定的2D-SiC/SiC复合材料拉伸循环加卸载应力-应变曲线与实测曲线吻合很好。通过Matlab编程得到2D-SiC/SiC复合材料单向加载时基体开裂过程图。结果表明,2DSiC/SiC复合材料失效时,基体裂纹分布相对比较均匀;基体裂纹数随应力单调增加,未出现持平段,表明材料失效时,基体裂纹还没有达到饱和。

In order to study the tensile damage behavior and the mechanical properties under low frequency cyclic loading of domestic 2D-SiC/SiC composites,their tensile loading/unloading behavior was investigated through experiments and a micromechanical approach.The stress-strain relationship of unidirectional continuous fiber reinforced ceramic matrix composites during loading,unloading and reloading was obtained by constructing a micromechanical model.The relationship between the number of matrix cracks and stress,and failure criterion of composites were obtained according to a fracture statistical method.Through stress changing,the model was applied to domestic 2D woven SiC/SiC composites.For monotonically tensile specimen,matrix Weibull modulus and interfacial shear resistance were gotten by using the orthogonal experiment and the least square method.Fiber Weibull modulus was obtained by making the failure strength of the predicted curve in good agreement with the experimental curve.The tensile loading/unloading stress-strain curve of 2D-SiC/SiC composites obtained with these parameters is in good agreement with the experimental result.The matrix cracking process associated with monotonic tension of 2D-SiC/SiC composites was also produced using Matlab.The results reveal that the matrix cracks are well-distributed when composites failure.The number of matrix cracks is monotone increasing with the raising stress,but it does not appear a platform,which is noted that matrix cracks have not been saturated when composites failure.