连续石墨纤维增强铝基复合材料准静态拉伸损伤演化与断裂力学行为

Damage evolution and fracture behaviors of continuous graphite fiber reinforced aluminium matrix composites subjected to quasi-static tensile loading

针对连续石墨纤维增强铝基(CF/Al)复合材料,采用三种纤维排布方式的代表体积单元(RVE)建立了其细观力学有限元模型,采用准静态拉伸试验与数值模拟结合的方法,研究了其在轴向拉伸载荷下的渐进损伤与断裂力学行为。结果表明,采用基体合金和纤维原位力学性能建立的细观力学有限元模型,对轴向拉伸弹性模量和极限强度的计算结果与实验结果吻合良好,而断裂应变计算值较实验结果偏低。轴向拉伸变形中首先出现界面和基体合金损伤现象,随应变增加界面发生失效并诱发基体合金的局部失效,最后复合材料因纤维发生失效而破坏,从而出现界面脱粘后纤维拔出与基体合金撕裂共存的微观形貌。细观力学有限元分析结果表明,在复合材料制备后纤维性能衰减而强度较低条件下,改变界面强度和刚度对复合材料轴向拉伸弹塑性力学行为的影响较小,复合材料中纤维强度水平是决定该复合材料轴向拉伸力学性能的主要因素。

According to the microstructure of the continuous graphite fiber reinforced aluminium matrix(CF/Al) composites, the micromechanical finite element model was established based on the representative volume element(RVE) with different fibre arrangements. The progressive damage and fracture behaviors of the CF/Al composites under axial tensile condition were investigated by quasi-static tensile testing and numerical simulation method. The results show that the axial tensile modulus and strength calculated by the micromechanical model with the diagonal quadrilateral fiber arrangement agree well with the experimental results, while the fracture strain is underestimated. At the first tensile stage, the interface damage initiates and accumulates. With the increase of strain, the interface damage induces the local interfacial debonding and matrix alloy failure at the middle stage. At the last stage, the occurrence of fiber failure leads to the eventual fracture of the composites, which results in a fracture surface with coexistence of matrix tearing and fiber pull out. According to the micromechanical calculation results, the influence of interfacial strength and stiffness on the axial tensile behavior is inapparent in the case of insufficient fiber strength, while the axial mechanical properties of the composite are primarily determined by the in-situ fiber ultimate strength.