This paper describes a newly proposed viscoelastic–viscoplastic constitutive model that is used to characterize the effective mechanical behaviors of fiber-reinforced composites based on micromechanical modeling. A homogenization approach is developed in which the effective stress of the fiber-reinforced composite is decomposed into an elastoplastic component and a viscous component. For the elastoplastic component, a bridge model is adopted to characterize the effective elastoplastic behaviors, while for the viscous component, homogenization theory applied to the time domain is utilized to describe the effective viscous responses. The overall stress for the composite can be obtained by superposing the stress contributions of the two components. The proposed micromechanics-based constitutive model has an explicit form, which contributes to the computational efficiency of the multiscale simulations for the composite structures. Unit cubes with 128 randomly distributed cylindrical fibers of equal size are created as the representative volume element models for numerical validation of the proposed constitutive model. The effects of fiber volume fraction, hardening law, loading condition, and strain rate are considered to comprehensively validate the constitutive model. Experimental results for IM7/8552 carbon fiber–reinforced composite were employed to validate the constitutive model. By comparing the model predictions to the experimental results and numerical observations, the constitutive model was found to provide acceptably good predictions of the viscoelastic–viscoplastic behaviors of the fiber-reinforced composites.

本文介绍了一种新提出的粘弹性-粘塑性本构模型，该模型用于基于微机械建模来表征纤维增强复合材料的有效力学行为。开发了一种均质化方法，其中纤维增强复合材料的有效应力分解为弹塑性成分和粘性成分。对于弹塑性分量，采用桥模型来表征有效弹塑性行为，而对于粘性分量，采用时域均质化理论来描述有效粘性响应。复合材料的总应力可以通过叠加两个组件的应力贡献来获得。所提出的基于微力学的本构模型具有明确的形式，这有助于提高复合结构多尺度模拟的计算效率。创建具有 128 个随机分布的相同大小的圆柱形纤维的单位立方体作为代表体积元模型，用于对所提出的本构模型进行数值验证。考虑纤维体积分数、硬化规律、加载条件和应变率的影响，综合验证本构模型。IM7/8552 碳纤维增强复合材料的实验结果用于验证本构模型。通过将模型预测与实验结果和数值观察进行比较，发现本构模型对纤维增强复合材料的粘弹-粘塑性行为提供了可接受的良好预测。