Shear Banding and Shear Fracture of Polycarbonate

休斯顿大学提出了一项为期三年的研究计划，旨在研究韧性聚合物（特别是聚碳酸酯）中的动态剪切带和剪切断裂现象。本文提出进行实验来表征聚碳酸酯的高应变率热力学行为，研究剪切带和剪切破坏以及相关的破坏模式转变，并将这些与已知表现出类似行为的金属材料的实验进行比较。采用分离式Hopkinson压杆和扭杆实验表征聚碳酸酯的高应变率本构行为；高速摄影结合光弹性和高速显微摄影将用于研究剪切带和破坏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局部化的发生和生长的作用。类似的实验将在金属材料中进行，也表现出剪切带/剪切破坏模式转变进行比较。这一基础研究将有助于更好地理解韧性聚合物剪切带和破坏模式转变的机理和力学。如果了解聚碳酸酯和一些金属材料之间观察到的相似行为的原因，这项工作将为广泛的材料中的剪切带提供见解。叠加静载荷或位移约束对破坏模式转变的影响可能对抗冲击损伤结构的设计具有重要的技术意义，并建议进行研究。

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.