This work presents a comprehensive phase-field framework for modeling anisotropic viscoelastic-viscoplastic fracture in short fiber-reinforced polymer (SFRP) composites under hygrothermal environments at finite deformation. The constitutive model employs a multiplicative decomposition of the deformation gradient into viscoelastic and viscoplastic components. An anisotropic phase-field formulation is developed using structural tensors to capture orientation-dependent fracture energy induced by multiple fiber families. Hygrothermal effects are incorporated through moisture-dependent swelling, thermal expansion, and temperature- and moisture-sensitive material parameters within the coupled framework. Numerical investigations demonstrate the framework's capability to capture complex fracture phenomena in SFRPs. Results reveal that fiber orientation fundamentally governs the spatial distribution of crack driving force, with maximum energy accumulation along fiber directions persisting throughout viscous relaxation. The anisotropy parameter controlling directional fracture resistance significantly influences crack path deflection. Hygrothermal degradation substantially reduces both peak load and fracture energy, with moisture absorption and elevated temperature each contributing to decreased mechanical performance. The framework captures the influence of fiber mechanical properties on global load-bearing capacity and crack propagation resistance. This unified computational framework advances the predictive modeling of damage evolution in SFRPs subjected to realistic environmental and mechanical loading conditions.

翻译：本研究提出了一个全面的相场框架，用于模拟有限变形下湿热环境中短纤维增强聚合物（SFRP）复合材料的各向异性粘弹性-粘塑性断裂。本构模型采用变形梯度的乘法分解，将其分解为粘弹性和粘塑性分量。通过引入结构张量，发展了一种各向异性相场公式，以捕捉由多族纤维引起的取向依赖性断裂能。在耦合框架中，通过依赖于湿度的膨胀、热膨胀以及温度和湿度敏感的材料参数，纳入了湿热效应。数值研究证明了该框架捕捉SFRP中复杂断裂现象的能力。结果表明，纤维取向从根本上控制了裂纹驱动力的空间分布，沿纤维方向的最大能量积累在整个粘性松弛过程中持续存在。控制方向性断裂阻力的各向异性参数显著影响裂纹路径偏转。湿热降解显著降低了峰值载荷和断裂能，吸湿和温度升高均导致力学性能下降。该框架捕捉了纤维力学性能对整体承载能力和裂纹扩展阻力的影响。这一统一的计算框架推进了SFRP在实际环境和机械载荷条件下损伤演化的预测建模。