基于率相关弹性-粘塑性损伤动态本构关系的复合材料渐进失效分析

Fiber reinforced composite materials are primary materials of engineering structures. Their material constitutive models play an important role in predicting failure loads and failure modes of composite laminates. Also, it is of significance in ensuring the safety of structures and avoiding human and economic losses. The mechanical behaviour of composite materials is complicated due to their various in-plane and out-of-plane failure modes, irreversible deformations and material properties degradation caused by damage initiation and evolution. Also, composite materials are often subjected to dynamic loading, under which they exhibit strain rate-dependent behaviour. Existing material constitutive models seldom simultaneously consider these factors. Also, finite element analyses using material models with strain-softening branch often exhibit computational difficulties and abort prematurely due to convergence problems.Therefore,it is challenging to accurately predict failure loads and failure modes of composite laminates...In the present research, a strain rate-dependent material constitutive model including the aforementioned factors will be developed based on the framwork of visco-plastic mechanics,damage mechanics and computational inelasticity. The material constitutive model includes a strain rate-dependent plastic model to describe the strain rate-dependent behaviour of composite materials and a damage model to consider various failure modes and material properties degradation due to damage development. Efficient algorithms will be developed and embeded in finite element procedure Abaqus. The material model will be validated through experiments conducted on composite coupons. It is suitable for the progressive failure analysis of composite materials subjected to static and dynamic loadings and will provide an effective way for accurately predicting their failure modes and failure loads and better ultilization of composite laminates.

复合材料的本构关系对准确预测相应工程结构破坏荷载及模式起着关键作用，对保障结构安全，避免重大经济损失和人员伤亡具有重要意义。其力学行为复杂，可发生各种破坏模式，产生不可逆变形；亦可因损伤萌生和累积致材料性能劣化等；且常处于动力加载状态，展现应变率相关性。现有模型较少同时考虑这些因素，且数值分析中若采用含应变软化段的材料模型，计算收敛性难以保证。故难以准确有效地预测其破坏荷载及模式。.本项目拟基于粘塑性力学、损伤力学及计算非弹性力学，提出一个同时考虑上述因素的应变率相关复合材料动态本构关系。模型包含一个率相关塑性模型和一个损伤模型分别描述复合材料的率相关动态行为和各种破坏模式及损伤累积导致的材料性能劣化。开发高效隐式迭代算法，嵌于已有有限元软件；设计并进行构件试验，验证模型的有效性。模型适用于复合材料静、动力加载情况，将为准确预测其破坏荷载和模式提供一种有效的分析方法，促进合理应用复合材料。

复合材料由于其优良的力学性能，抗疲劳和耐腐蚀性能等，被广泛应用于民用与军用工程领域。但是，复合材料基体与纤维材料的力学属性截然不同导致其力学行为和破坏模式极其复杂，比如塑性变形，应变率效应和损伤累积导致材料属性退化等；并且复合材料成本昂贵，在某种程度上限制了复合材料更大范围地使用。因此有必要开发能够准确描述复合材料力学行为，预测破坏荷载和模式的本构关系，为设计出安全高效率的复合材料构件及结构提供指导方法。. 本项目研究提出了一个新的复合材料应变率相关弹性-粘塑性损伤本构模型，模型能够更好地描述复合材料在各种应变率加载条件下所展示的力学行为特性，包括塑性变形，应变率效应和损伤累积导致的材料属性退化。模型用于描述复合材料从加载开始到最终破坏的力学行为。本项目推导了模型的隐式数值积分算法，推导与所开发的算法相应的数值一致性切线刚度矩阵，该数值计算方法可保证有限元分析中采用Newton-Raphson方法解答非线性问题时的二阶收敛性，保证整体计算的收敛性、有效性和计算精度。本项目开发了与本构模型算法相应的基于有限元程序Abaqus的用户自定义材料子程序UMAT，可嵌套在Abaqus中用于预测复合材料在各种应变率加载条件下的破坏荷载和破坏模式及用于复合材料构件和结构的渐进失效分析。对模型进行了试验验证，通过对力学行为展示显著塑性效应和应变率效应的S2/8552复合材料层合板进行渐进失效分析验证模型的有效性。计算结果展示本模型预测得到的在不同应变率作用下的应力应变曲线与试验曲线符合良好。. 本项目开展复合材料非线性行为与破坏机理的研究，可为复合材料结构设计理论提供依据。从不必通过加大安全系数来保证复合材料结构安全性，避免结构过度设计，减少材料消耗的角度看，本项目具有难以估量的社会和经济效益。