Experimental and phenomenological investigations on the strain rate sensitivity of rigid PVC foams at strain rates of 0.005 s−1 to 600 s−1

Abstract

Polymeric foams are often subjected to high strain rates in various industrial applications, especially the transportation sector, and experience significant deformations. An in-depth comprehension of the dynamic mechanical characteristics of polymeric foam is essential for devising effective engineering design approaches. Previous studies have extensively utilized Split Hopkinson Pressure Bar (SHPB) apparatuses to test polymeric foams dynamically; however, these studies faced technical limitations in specimen size, preventing compliance with the ASTM D1621 standard test method for rigid cellular plastics. A customized pneumatic apparatus equipped with a massive impacting bullet and sacrificial excess energy absorbing system was employed to complete the mechanical material characterization of Polyvinyl Chloride (PVC) foams, following the ASTM D1621 standard, to address previous technical limitations. PVC foams with six different nominal densities were subjected to strain rates ranging from 0.005 s−1 to 600 s−1. Loading was conducted parallel and perpendicular to the foam rise direction to investigate dynamic anisotropic material characteristics. A comparison of tests conducted at strain rates of 0.005 s−1 and 400 s−1 revealed an average increase of 35.1 % in the plateau stress. The phenomenological Nagy model was combined with a nonlinear Avalle relationship and revised with a new term, supported by findings from the present study, to characterize the complete stress/strain response, for the range of strain rates considered in this research. The calibrated model exhibited an average error of 1.7 % in the predicted plateau stress. The results indicated that testing under a single dynamic strain rate was sufficient to characterize the rate sensitivity of the PVC foam in the dynamic regime. Furthermore, the influence of relative density on the foam rate sensitivity was quantified, revealing a plateau in the strength enhancing effect of density at a nominal relative density of 0.125.