Shear Banding and Shear Fracture of Polycarbonate

Ravi-Chandar 9700449 休斯敦大学提议开展一项为期三年的工作，旨在研究延性聚合物（特别是聚碳酸酯）中的动态剪切带和剪切断裂现象。 建议进行实验来表征聚碳酸酯的高应变率热机械行为，研究剪切带和剪切失效以及相关的失效模式转变，并将这些实验与已知表现出类似行为的金属材料的实验进行比较。 分体式霍普金森压杆和扭杆实验将用于表征聚碳酸酯的高应变率本构行为； 高速摄影与光弹性和高速显微摄影相结合将用于研究剪切带和失效模式转变的力学和机制；使用高速红外探测器的温度测量将用于检查温​​度对剪切带定位的开始和增长的作用。 类似的实验将在也表现出剪切带/剪切破坏模式转变的金属材料中进行，以进行比较。 这项基础研究将有助于更好地理解延性聚合物中剪切带和失效模式转变的机制和力学。 如果理解了所观察到的聚碳酸酯和某些金属材料行为之间相似的原因，这项工作将有助于深入了解各种材料中的剪切带。 叠加静态载荷或位移约束对失效模式转换的影响可能对抗冲击损坏结构的设计产生重大技术影响，建议进行研究。

Ravi-Chandar 9700449 The University of Houston proposes a three-year effort aimed at investigating the phenomenon of dynamic shear banding and shear fracture in ductile polymers, specifically polycarbonate. It is proposed to perform experiments to characterize the high strain-rate thermomechanical behavior of polycarbonate, to study shear banding and shear failure and the associated failure mode transitions, and to compare these with experiments on the metallic materials that are known to exhibit a similar behavior. Split Hopkinson pressure bar and torsion bar experiments will be used to characterize the high strain rate constitutive behavior of polycarbonate; high speed photography combined with photoelasticity and high speed photomicrography will be used to investigate the mechanics and mechanisms of shear banding and failure mode transitions; temperature measurements using high speed infrared detectors will be used to examine the role of temperature on the onset and growth of the shear banding localization. Similar experiments will be performed in a metallic material that also exhibits shear banding/shear failure mode transitions for comparison. This basic research will lead to a better understanding of the mechanisms and mechanics of shear banding and failure mode transitions in ductile polymers. If the reasons for the similarities between the observed behavior of polycarbonate and some metallic materials are understood, this work will provide insight into shear banding in a wide range of materials. The effect of superimposed static loading or displacement constraints on failure mode transitions could have significant technological implications for the design of structures resistant to impact damage and is proposed to be investigated.