Amorphous polymers exhibit a viscoplastic strain hardening behavior at large strains. To describe this hardening behavior, we have developed an effective temperature model for the nonequilibrium behavior of amorphous polymers that incorporate the effects of network orientation and relaxation at large plastic deformation. The development of network orientation is introduced as a backstress that produces kinematic hardening in the stress response, while network relaxation describes the effects of temperature and strain rate on the hardening response. The model was applied to simulate the thermomechanical behavior of polycarbonate (PC) to determine the model parameters from standard dynamic frequency sweep and differential scanning calorimetry tests. The simulation results showed that the model can quantitatively capture the dependence of the hardening modulus on strain, strain rate, and temperature, as well as the unloading and reloading behavior measured in uniaxial compression tests. We applied the model to investigate the effect of plastic dissipation on the peeling of a polymer filament from a rigid substrate to guide the design of peel tests to measure the intrinsic fracture toughness of polymers fabricated by melt extrusion additive manufacturing processes.

非晶态聚合物在大应变下表现出粘塑性应变硬化行为。为了描述这种硬化行为，我们为非晶聚合物的非平衡行为开发了一个有效的温度模型，该模型结合了网络取向和大塑性变形时松弛的影响。网络定向的发展是作为背应力引入的，它在应力响应中产生运动硬化，而网络松弛描述了温度和应变速率对硬化响应的影响。该模型用于模拟聚碳酸酯（PC）的热机械行为，以通过标准动态频率扫描和差示扫描量热法测试确定模型参数。仿真结果表明，该模型可以定量捕获硬化模量对应变，应变速率和温度的依赖性，以及在单轴压缩试验中测得的卸载和再加载行为。我们应用该模型研究了塑性耗散对聚合物长丝从刚性基材上剥离的影响，以指导剥离测试的设计，以测量通过熔融挤出添加剂制造工艺制造的聚合物的固有断裂韧性。