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.
