The usage of short fiber reinforced thermoplastics has been increasing in many industries recently. These composites have many advantages such as high specific strength, lightweight, wear and rust resistance, high stiffness, fast processing rate, and relatively low manufacturing cost. Multiaxial cyclic loading and non-proportionality between different loading sources are inevitable in many applications with such materials. In this study, the multiaxial fatigue behavior of short glass fiber reinforced thermoplastics under different environmental and loading conditions is modeled using a critical plane-based damage approach. This model was recently used for uniaxial fatigue life prediction of Short Fiber Reinforced Thermoplastic Composites. In this paper the model is applied to a large amount of experimental multiaxial fatigue data, demonstrating significantly better correlations than other models used in the literature. The effects of fiber orientation, stress state, mean stress, and stress concentration on multiaxial fatigue behavior are considered in the model. Temperature and frequency effects on multiaxial fatigue behavior were also included by applying the proposed damage model into a general fatigue model. Model predictions are presented and discussed by comparing them with experimental data from the literature.

近年来，短纤维增强热塑性塑料在许多行业的使用不断增加。这些复合材料具有比强度高、重量轻、耐磨防锈、刚度高、加工速度快、制造成本相对较低等优点。在此类材料的许多应用中，多轴循环载荷和不同载荷源之间的不成比例是不可避免的。在这项研究中，使用基于临界平面的损伤方法对短玻璃纤维增​​强热塑性塑料在不同环境和载荷条件下的多轴疲劳行为进行了建模。该模型最近用于短纤维增强热塑性复合材料的单轴疲劳寿命预测。在本文中，该模型应用于大量实验多轴疲劳数据，显示出比文献中使用的其他模型明显更好的相关性。模型考虑了纤维取向、应力状态、平均应力和应力集中对多轴疲劳行为的影响。通过将所提出的损伤模型应用到通用疲劳模型中，还包括了温度和频率对多轴疲劳行为的影响。通过将模型预测与文献中的实验数据进行比较来提出和讨论。