Nonlinear properties of metal matrix composites (MMCs) are studied. The research combines results of loading–unloading tensile tests, microstructural observations and numerical predictions by means of micromechanical mean-field models. AA2124/SiC metal matrix composites with SiC particles, produced by the Aerospace Metal Composites Ltd. (AMC) are investigated. The aluminum matrix is reinforced with 17% and 25% of SiC particles. The best conditions to evaluate the current elastic stiffness modulus have been assessed. Tensile tests were carried out with consecutive unloading loops to obtain actual tensile modulus and study degradation of elastic properties of the composites. The microstructure examination by scanning electron microscopy (SEM) showed a variety of phenomena occurring during composite deformation and possible sources of elastic stiffness reduction and damage evolution have been indicated. Two micromechanical approaches, the incremental Mori–Tanaka (MT) and self-consistent (SC) schemes, are applied to estimate effective properties of the composites. The standard formulations are extended to take into account elasto-plasticity and damage development in the metal phase. The method of direct linearization performed for the tangent or secant stiffness moduli is formulated. Predictions of both approaches are compared with experimental results of tensile tests in the elastic–plastic regime. The question is addressed how to perform the micromechanical modelling if the actual stress–strain curve of metal matrix is unknown.

研究了金属基复合材料（MMC）的非线性特性。该研究通过微机械平均场模型结合了装卸拉伸试验，微观结构观察和数值预测的结果。研究了航空金属复合材料有限公司（AMC）生产的具有SiC颗粒的AA2124 / SiC金属基复合材料。铝基质用17％和25％的SiC颗粒增强。已经评估了评估当前弹性刚度模量的最佳条件。使用连续的卸料环进行拉伸试验，以获得实际的拉伸模量并研究复合材料的弹性性能下降。通过扫描电子显微镜（SEM）进行的微观结构检查显示出复合变形过程中发生的各种现象，并指出了弹性刚度降低和损伤发展的可能来源。两种微机械方法，即增量Mori-Tanaka（MT）和自洽（SC）方案，可用于估算复合材料的有效性能。扩展了标准配方，以考虑到弹塑性和金属相中的损伤发展。制定了针对切线或割线刚度模量执行的直接线性化方法。将两种方法的预测结果与弹塑性试验中的拉伸试验的实验结果进行比较。