Glassy polymers exhibit a strong thermomechanical coupling when subjected to mechanical loading. A homogeneous strain distribution can be achieved in uniaxial compression conditions. However, a clear temperature increase is observed when the loading rate is relatively high, which further results in a decrease in stress due to thermal softening. In tensile tests, necking instability can easily occur. A temperature change is accompanied by the nucleation and propagation of necked regions. In this work, we apply the effective temperature theory, which can capture the nonequilibrium structure evolution of amorphous polymers, to investigate the thermomechanical behavior of glassy polymers. We demonstrate that a finite element model based on the effective temperature theory can well capture the stress response and the temperature increase of polycarbonate (PC) compressed at different loading rates. We further combine experiments and simulations to investigate the effects of the loading rate and aging treatment on the necking behavior in amorphous glassy polymer poly(ethylene terephthalate)-glycol (PETG) in uniaxial tension loading tests. Through employing digital image correlation and infrared thermometry, the strain distribution and the temperature field can be fully characterized during the formation and propagation of necked regions. The model captures all important features of localization behavior observed in experiments, including the force–displacement relationship, and the strain and temperature distribution with necking propagation. However, it underestimates the maximum strain and temperature when the displacement is large. Both experimental and simulative results indicate that increasing loading rate and aging time can induce an increase of the intrinsic strain softening due to a more active structural state caused by mechanical rejuvenation. This further leads to more pronounced localized behavior and a ductile–brittle transition. Our work proves that the effective temperature model is a powerful theoretical framework to predict the complex thermomechanical response of glassy polymers.

玻璃态聚合物在受到机械载荷时表现出强烈的热机械耦合。在单轴压缩条件下可以实现均匀的应变分布。然而，当加载速率相对较高时，观察到明显的温度升高，这进一步导致由于热软化导致的应力降低。在拉伸试验中，很容易出现颈缩不稳定性。温度变化伴随着颈缩区域的成核和扩展。在这项工作中，我们应用有效温度理论来研究玻璃态聚合物的热机械行为，该理论可以捕捉无定形聚合物的非平衡结构演化。我们证明了基于有效温度理论的有限元模型可以很好地捕捉在不同加载速率下压缩的聚碳酸酯 (PC) 的应力响应和温度升高。我们进一步结合实验和模拟来研究加载速率和老化处理对单轴拉伸加载试验中无定形玻璃状聚合物聚（对苯二甲酸乙二醇酯）-乙二醇（PETG）的颈缩行为的影响。通过采用数字图像相关和红外测温技术，可以充分表征颈缩区域形成和扩展过程中的应变分布和温度场。该模型捕获了实验中观察到的定位行为的所有重要特征，包括力-位移关系，以及随着颈缩传播的应变和温度分布。但是，它低估了位移较大时的最大应变和温度。实验和模拟结果都表明，增加加载速率和老化时间可以导致固有应变软化增加，这是由于机械再生引起的更活跃的结构状态。这进一步导致更明显的局部行为和韧性-脆性转变。我们的工作证明，有效温度模型是预测玻璃态聚合物复杂热机械响应的强大理论框架。实验和模拟结果都表明，增加加载速率和老化时间可以导致固有应变软化增加，这是由于机械再生引起的更活跃的结构状态。这进一步导致更明显的局部行为和韧性-脆性转变。我们的工作证明，有效温度模型是预测玻璃态聚合物复杂热机械响应的强大理论框架。实验和模拟结果都表明，增加加载速率和老化时间可以导致固有应变软化增加，这是由于机械再生引起的更活跃的结构状态。这进一步导致更明显的局部行为和韧性-脆性转变。我们的工作证明，有效温度模型是预测玻璃态聚合物复杂热机械响应的强大理论框架。