Dynamic-Tensile-Extrusion for investigating large strain and high strain rate behavior of polymers

Abstract

Dynamic-Tensile-Extrusion (Dyn-Ten-Ext) is a novel test method for the investigation of material response under extreme tensile conditions, comprising the combined conditions of large tensile strains (ɛ > 1) and high strain rates (dɛ/dt > 10,000 s−1), effectively serving as a tensile analog to the Taylor cylinder impact test. The ability to apply this mechanical state is particularly useful for elucidating the deformation and damage responses of polymers under extreme mechanical conditions since they are more ductile, rate-dependent and sensitive to hydrostatic tension than other engineering materials. The technique, in general, generates stable extruded polymer jets that are observed via high-speed photography undergoing large tensile strains at high rates. These jets may accumulate subcritical damage during deformation, revealing damage processes that may only activate in a principally tensile deformation. Ultimately, the jet ruptures, either progressively due to damage or catastrophically. Dyn-Ten-Ext produces spatially and temporally heterogeneous deformation fields, making it an integrated test, analogous to Taylor Impact. The range of strains and strain rates that evolve throughout the test, combined with the simple well defined boundary conditions, produce outstanding datasets for the validation of material models under conditions not accessible by classic testing techniques. This work presents an overview of Dyn-Ten-Ext as a technique for investigating extreme tensile deformation and damage in polymers with representative results for the elastomer polyurea and semicrystalline polymers high density polyethylene, polytetrafluoroethylene, and polychlorotrifluoroethylene.