48. Effects of Pressure and Strain Rate on the Mechanical Behavior of Glassy Polymers

In this study the mechanical response of transparent polymers under varying strain rates and hydrostatic pressures is investigated. Quasi-static and dynamic tests are performed under uniaxial and multi-axial loadings and the effect of hydrostatic pressure on the response of the material is explored. In both quasi-static and dynamic experiments, the confinement pressure was increased to a predetermined level and kept constant during the test. This test subjects specimens to confining pressure (up to 200 MPa) prior to loading. Loading was either applied quasi-statically using a servo-hydraulic load frame or at dynamic rates using a modified SHPB. The strain rate dependency of the Polycarbonate material is studied using an Instron UTM and split Hopkinson pressure bar (SHPB) technique. Digital image correlation is used to record full field deformation and calculate the strain. Ultra-high strain rate tests are also performed using a micro-Kolsky bar and small (50–100 um length) specimens. The confinement experiments show that the yield stress is linearly proportional to the confinement pressure but the elastic modulus is insensitive to confinement pressure. Significant rate sensitivity is observed at moderate strain rates and becomes insensitive to strain rate at the highest strain rates measured.