Damage theory of discontinuously-reinforced composites with reinforcement cracking and mechanism to produce high performance

在颗粒或短纤维增强复合材料中，增强体的开裂损伤和水泥-基体界面的脱粘损伤从变形早期就开始发展，并影响复合材料的力学性能。本研究发展了复合材料的增量损伤理论，并根据数值计算和实验结果讨论了损伤对非连续增强复合材料力学性能的影响。所得结果总结如下.基于细观力学方法，建立了非连续增强复合材料的损伤理论，该理论能够描述增强体的渐进剥离或开裂损伤以及基体的塑性。在此基础上，引入损伤理论，建立了有限元分析方法.研究了玻璃粒子增强尼龙66复合材料的损伤过程及其对力学性能的影响。脱粘损伤降低了材料的抗拉强度和疲劳强度，提高了材料的断裂韧性和抗疲劳裂纹扩展能力.基于损伤理论分析了玻璃颗粒增强尼龙66复合材料的拉伸应力应变关系和裂纹尖端场。实验和数值计算结果表明，复合材料的力学性能是完整硬质颗粒和脱粘损伤相互竞争的结果.为了探索形状记忆合金复合材料的潜力，建立了复合材料在热机械载荷作用下的本构关系，并对TiNi-聚碳酸酯复合材料的变形和强度进行了测试，得出了制备高性能复合材料的一些建议。

In the particle or short-fiber reinforced composites, cracking damage of reinforcements and debonding damage of reinforcement-matrix interface develop from early stage of deformation, and affect the mechanical performance of the composites. In this project, an incremental damage theory of the composites has been developed, and an influence of damage on the mechanical performance of the discontinuously-reinforced composites has been discussed based on the numerical and experimental results. Obtained results are summarized as follows.1. A damage theory of the discontinuously-reinforced composites, which can describe the progressive debonding or cracking damage of reinforcements and the matrix plasticity, was established based on the micromechanics approach. Furthermore, a finite element method was developed by introducing the damage theory.2. The damage process and the influence of damage on the mechanical performance were examined on glass-particle-reinforced nylon 66 composites in which the particle content and interfacial strength were changed. The debonding damage reduces the tensile strength and fatigue strength, and enhances the fracture toughness and fatigue crack growth resistance.3. Tensile stress-strain relation and crack-tip field of glass-particle-reinforced nylon 66 composites were analyzed based on the damage theory. It was found from the experimental and numerical results that the mechanical performance of the composites are obtained as the results of the competitive effects of the intact hard particles and the debonding damage.4. In order to investigate the potentiality of the shape memory alloy composites, a constitutive relation of the composites under thermo-mechanical loading were developed and the deformation and strength of TiNi-poly carbonate composites were tested.From the above results, many suggestions to produce the composite with high-performance were obtained.