Due to the injection molding process, short fiber-reinforced thermoplastic composites show a complex fiber orientation distribution and, as a consequence, an overall anisotropic mechanical behavior. The monotonic and cyclic mechanical behavior of PolyEtherEtherKetone thermoplastic reinforced with 30 wt.% of short carbon fibers was characterized through a series of tests generating various complex loading histories (loading–unloading with creep or recovery steps, cyclic loading with various stress amplitudes) performed at room temperature on samples with various homogeneous and heterogeneous fiber orientation distributions. A three-dimensional model relying on a thermodynamic framework was then developed to represent the anisotropic mechanical behavior of the material, including elastic, viscoelastic, and plastic phenomena. Relevant constitutive laws were defined to describe the phenomena within wide ranges of loading rates and levels, with a limited number of parameters. Elastic anisotropy and plastic anisotropy were naturally described by using a two-step homogenization method and a Hill-like equivalent stress taking into account the fiber orientation distribution. The model was implemented into a finite element code to be able to simulate the response of complex parts with a heterogeneous fiber orientation distribution subjected to a heterogeneous loading. Model parameters were identified by applying a robust and original approach relying on a limited number of relevant experiments. The prediction capability of the model was demonstrated by simulating several types of tests not used for the identification, covering a wide range of monotonic and cyclic, homogeneous and heterogeneous, loading conditions, for various simple and complex fiber orientation distributions. In particular, the model is shown to be able to predict the energy dissipated in the material when subjected to cyclic loading.

由于注射成型工艺，短纤维增强的热塑性复合材料显示出复杂的纤维取向分布，因此具有整体各向异性的机械性能。通过一系列测试，表征了由30 wt。％的短碳纤维增强的PolyEtherEtherKetone热塑性塑料的单调和循环力学行为，这些测试产生了各种复杂的加载历史（加载-蠕变或恢复步骤的卸载，具有不同应力幅度的循环加载）。室温下具有各种均质和非均质纤维取向分布的样品。然后开发了一个依赖于热力学框架的三维模型来表示材料的各向异性力学行为，包括弹性，粘弹性和塑性现象。定义了相关的本构定律，以有限的参数数量来描述各种加载速率和水平范围内的现象。考虑到纤维取向分布，通过使用两步均化方法和希尔式等效应力自然地描述了弹性各向异性和塑性各向异性。该模型被实现为有限元代码，能够模拟具有异质纤维取向分布且受异质载荷作用的复杂零件的响应。通过使用有限的相关实验，采用可靠且原始的方法来确定模型参数。通过模拟几种未用于识别的测试类型来证明模型的预测能力，这些测试涵盖了广泛的单调和循环，均匀且不均匀的加载条件，适用于各种简单和复杂的纤维方向分布。尤其是，该模型显示出能够预测材料在承受周期性载荷时耗散的能量。