进行了体积含量为55%的高体积分数SiC_P/Al合金复合材料拉伸特性实验, 发现其应力--应变曲线具有明显的非线性特征.断口分析结果表明: 高体积分数SiC_P/Al合金复合材料呈现典型的脆性平齐断口, SiC颗粒形状很不规则, 且带有尖角, 材料内部存在孔洞、微裂纹、界面脱黏等微观缺陷. 针对断口分析结果, 提出了两端带尖角的多边棱柱颗粒的体积单胞和组合单胞模型, 适用于模拟SiC_P/Al合金复合材料颗粒形状不规则以及分布不均匀的情况, 具有较好的预测精度. 建立了含缺陷体积单胞和组合单胞模型, 预测结果表明, 界面脱黏是高体积分数SiC_P/Al复合材料拉伸应力--应变呈现非线性的主要原因.

SiC_P/Al alloy is one of most competitive particle reinforced metal matrix composite materials. For the SiC_P/Al alloy composites that volume fraction is lower than 25%, the mechanical properties were well known since many researcher worked hard in recent years. But when the volume fraction is higher than 35%, the mechanical properties of SiC_P/Al alloy were not understood so well. In this paper, the tension properties were tested for the high volume fraction (55%) SiC_P/Al alloy composites, the stress~strain curve showed obvious nonlinear properties. Macroscopic and microscopic fractography indicated that the fracture section of high volume fraction SiC_P/Al alloy looks flat like traditional brittle materials, the shape of SiC particle was irregular and with sharp angle, some micro--defects such as void, crack and interface debonding exist inside the materials. A cell volume element model of polygonal prism with sharp angle at both ends was developed to simulate the mechanical behavior of high volume fraction. This model could simulate the irregular shape and uneven distribution of the SiC particle. Furthermore, the volume element cell and multi--particles combined cell with defects were built to consider the effect of the void and interface debonding. The analysis results showed that the interface debonding was the most important cause of the nonlinear mechanical behavior of high volume fraction SiC_P/Al alloy composites.