In the present work we develop a thermodynamically consistent, large deformation homogenized constitutive model to predict high-temperature oxidation in fiber-reinforced polymer matrix composites (FRPMCs). The presence of fibers introduces anisotropy in the diffusion and the chemical reactions prevailing oxidation for these composite materials, resulting in heterogeneous shrinkage and stress distribution within the representative material volume. To model such behavior, we develop a homogenized approach considering a unidirectional composite RVE as a mixture of fibers and matrix, represented by the fiber volume fractions and their respective orientations. In what follows, we develop a coupled chemo-mechanical model to predict the oxidation response of this highly anisotropic composite material, based on an earlier developed multiphysics theory of bulk polymer’s oxidation. We numerically implement the proposed model in finite elements by writing a user element subroutine (UEL) in ABAQUS/Standard and perform various simulations in 2-D and 3-D composites RVE. The results demonstrate that the proposed model is capable of predicting several important characteristics of oxidation in fiber-reinforced composites, such as, preferential growth of oxide layer, heterogeneous distribution of residual stress, and the effect of fiber volume fraction on the oxidation process.

在目前的工作中，我们开发了一种热力学一致的大变形均质本构模型，以预测纤维增强聚合物基复合材料 (FRPMC) 中的高温氧化。纤维的存在在扩散和化学反应中引入了各向异性，这些化学反应主要用于这些复合材料的氧化，导致代表性材料体积内的不均匀收缩和应力分布。为了模拟这种行为，我们开发了一种均质化方法，将单向复合材料 RVE 视为纤维和基体的混合物，由纤维体积分数和它们各自的方向表示。在下文中，我们开发了一个耦合化学机械模型来预测这种高度各向异性复合材料的氧化响应，基于早期开发的本体聚合物氧化的多物理场理论。我们通过在 ABAQUS/Standard 中编写用户单元子程序 (UEL) 并在 2-D 和 3-D 复合材料 RVE 中执行各种模拟，在有限元中数值实现所提出的模型。结果表明，所提出的模型能够预测纤维增强复合材料中氧化的几个重要特征，例如氧化层的优先生长、残余应力的不均匀分布以及纤维体积分数对氧化过程的影响。