High Strain Rate Experimental Characterization of Mode II Interlaminar Shear Response of UHMWPE Film Composites

Author(s):

Frank D. Thomas, Subramani Sockalingam, Michael A. Sutton, C. Allan Gunnarsson, Tusit Weerasooriya, and Stephen L. Alexander

Abstract:

To accurately model delamination behavior in ballistic impact simulations of laminated composite materials, interfacial traction– separation parameters must be experimentally determined. For material systems such as ultra-high-molecular-weight polyethylene (UHMWPE) films, which exhibit a high degree of strain-rate dependency in their mechanical response, high strain rate (HSR) characterization methodologies are needed for obtaining material deformation and failure behavior as a function of loading rate, especially to obtain the delamination response. This report discusses a new method using a tensile split-Hopkinson pressure bar to induce simple shear in a pre-cracked specimen for the purpose of extracting Mode II traction–separation parameters. Experiments are performed on UHMWPE Tensylon composites, and digital image correlation is used to extract full-field displacement and strain data for analysis. In this study, local shear strain rates on the order of 104 s–1 are reached in the specimen, and results are compared to equivalent quasi-static values. Linear increases in shear strength and apparent interfacial stiffness are observed, and the energy release rate appears to vary quadratically with strain rate. This study provides a methodology for obtaining HSR Mode II shear fracture response in laminated composites.