Experimental, numerical and analytical investigations on the elevated strain rate compressive behavior of high-performance PES foam up to 200 s−1

Abstract

The capability of operation in high-temperature environments makes high-performance polymeric foams superior to conventional foams in leading industries such as aviation. Mechanical properties of conventional polymeric foams have been well studied. However, fewer investigations have been done on their high-performance counterparts, especially under dynamic loadings. In this study, the compressive behavior of a high-performance polymeric foam, namely, closed-cell polyethersulfone (PES) foam, was investigated under quasi-static and elevated strain rates of loading. Three orthogonal loading directions (i.e., parallel and perpendicular to foam rise directions) were considered to investigate the PES foam's anisotropic behavior. The elevated strain rate tests were carried out utilizing a customized drop tower apparatus equipped with a cutter-extrusion energy dissipation system at the strain rate range of 50 to 200 s−1. A strain rate effect on the PES foam's compressive response with different densities was observed through increased compressive strength and plateau stress when loading parallel to the foam rise direction. This strain rate effect is more significant for higher densities. Moreover, anisotropic compressive behavior was observed when loading in different material directions. The PES foam's microstructure was investigated employing the Scanning electron microscope (SEM) technique. All dynamic tests were photographed utilizing a high-speed camera. It was found that the deformation was highly localized when loading in the foam rise direction. A series of equations were developed to quantify the localized deformation of polymeric foams based on the specimen's instantaneous dimensions during dynamic compression testing. For PES foam with different densities, the localized strain rates were approximately 6.3 times higher than the nominal values. Both the quasi-static and elevated compressive responses of the PES foam were numerically simulated using the explicit Finite Element Analysis (FEA) package LS-DYNA. Numerical models developed in this study can precisely predict the experimental stress/strain responses with a very high average validation metric of 97%. In addition, the mechanical response of PES foam with different densities has been successfully predicted using calibrated analytical models.