Ductile polymers have been increasingly applied in engineering applications to enhance the structural reliability under impact loading. Due to the limitation of experimental setup to achieve large tensile deformation and the difficulty to achieve dynamic force equilibrium, the localization and post-necking stages up to fracture of ductile polymers at high strain rates have less been investigated. In the present work, the dynamic strain localization of ductile polymeric rods under large tensile deformation up to fracture is studied on the bespoke Hopkinson tension bar synchronized with a high-speed camera. Transparent polycarbonate (PC) is used as a model material in the present study. Likewise, the constitutive response and fracture behaviour of polycarbonate are also characterized with the assistance of Digital Image Correction (DIC) from low to high strain rates under various temperature conditions. The results quantitatively show that the dynamic local strain rate initially increases dramatically to 200 % of the nominal strain rate due to strain localization. This is followed by a rapid drop with necking propagation, and finally tends to stay at strain rate of approximately 20 % of the nominal strain rate until fracture. The elevated temperatures would result in higher local strain rates. Two constitutive models with and without the consideration of constant strain rate condition are constructed for PC and incorporated in finite element simulations. The trend of dynamic local strain rate history with respect to nominal strain rate is successfully reproduced in simulations. The constitutive models particularly the simple dynamic amplification model, are able to reflect the phenomenological key features of the experimentally observed macroscopic and local responses of polycarbonate, and would find their potential applications in impact resistant transparency design.

韧性聚合物越来越多地应用于工程应用中，以提高冲击载荷下的结构可靠性。由于实现大拉伸变形的实验设置的限制和难以实现动态力平衡，在高应变速率下，韧性聚合物的局部化和后颈缩阶段直至断裂的研究较少。在目前的工作中，在与高速相机同步的定制霍普金森拉杆上研究了韧性聚合物棒在大拉伸变形下的动态应变局部化直至断裂。在本研究中，透明聚碳酸酯 (PC) 被用作模型材料。同样地，在数字图像校正 (DIC) 的帮助下，聚碳酸酯的本构响应和断裂行为也可以在各种温度条件下从低应变率到高应变率进行表征。结果定量地表明，由于应变局部化，动态局部应变率最初急剧增加到标称应变率的 200%。随后随着颈缩传播快速下降，最后趋向于保持在标称应变率的大约 20% 的应变率直至断裂。升高的温度将导致更高的局部应变率。为 PC 构建了考虑和不考虑恒定应变率条件的两个本构模型，并结合到有限元模拟中。在模拟中成功再现了动态局部应变率历史相对于名义应变率的趋势。本构模型特别是简单的动态放大模型，能够反映实验观察到的聚碳酸酯宏观和局部响应的现象学关键特征，并将在抗冲击透明设计中找到它们的潜在应用。