Abstract Thermoplastic polymers (TP) are well-suited for thermoforming and injection moulding processes. Semi-crystalline polymers (SCP) are a specific class of TPs, which partly crystallize after cooling from the melt. During thermoforming processes, SCPs are subjected to large deformations and thermal loadings and show strong thermo-mechanical coupling effects. In addition, the evolution of the crystalline phase influences the macroscopic material response significantly. Due to these complex dependencies, a demand for computational models arises, to analyze, predict, and optimize the complex material and structural behavior of parts during these processes. To this end, a finite strain, thermo-mechanically coupled constitutive framework is derived in a thermodynamically consistent manner for SCPs. In the continuum model, a visco-hyperelastic network resistance and an elasto-plastic intermolecular resistance are introduced, where non-linear isotropic and kinematic hardening as well as non-linear relaxation behavior are considered. To account for the dependence of the material response on the degree of crystallinity, the crystallization kinetics during cooling from the melt are captured by means of a non-isothermal representation of the Avrami equation. Furthermore, the heat generation, associated with irreversible processes and exothermic crystal growth, is derived in a thermodynamically consistent manner. Uniaxial tensile test data for different temperatures, loading rates, and degrees of crystallinity, as well as isothermal and non-isothermal differential scanning calorimetry (DSC) data for Polyamide 6 is utilized to calibrate the model in a stepwise parameter identification scheme. The model response is discussed and reveals the promising potential of this new approach to efficiently and accurately predict this class of materials in the future.

中文翻译：

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将结晶度分布纳入半结晶聚合物的热机械耦合本构模型

摘要 热塑性聚合物 (TP) 非常适用于热成型和注塑成型工艺。半结晶聚合物 (SCP) 是一类特殊的 TP，在从熔体冷却后部分结晶。在热成型过程中，SCP 会受到大变形和热载荷的影响，并表现出强烈的热机械耦合效应。此外，晶相的演变显着影响宏观材料响应。由于这些复杂的依赖关系，需要计算模型来分析、预测和优化这些过程中零件的复杂材料和结构行为。为此，以热力学一致的方式为 SCP 推导出有限应变、热机械耦合的本构框架。在连续模型中，引入了粘超弹性网络阻力和弹塑性分子间阻力，其中考虑了非线性各向同性和运动硬化以及非线性松弛行为。为了说明材料响应对结晶度的依赖性，从熔体冷却过程中的结晶动力学通过 Avrami 方程的非等温表示来捕获。此外，与不可逆过程和放热晶体生长相关的热量产生以热力学一致的方式导出。不同温度、加载速率和结晶度的单轴拉伸试验数据，以及聚酰胺 6 的等温和非等温差示扫描量热 (DSC) 数据用于在逐步参数识别方案中校准模型。讨论了模型响应，并揭示了这种新方法在未来高效准确地预测此类材料的潜力。