Low velocity impact on crash components with steel skins and polymer foam cores

Abstract

 The mechanical properties of XPS and EPP depend strongly on the foam density  XPS and EPP are found to be strain-rate sensitive even at low strain rates  XPS absorbs more energy than EPP in quasi-static indentation tests  The core material is found to be of less importance in dynamic tests  The foam density in an efficient energy absorber should be as low as possible

Sandwich Panels with Polymeric Foam Cores Exposed to Blast Loading: An Experimental and Numerical Investigation

“…The manufacturer designates XPS with the nominal plateau stress of the foam in kPa, and the three densities considered here are thus named XPS-250, XPS-400 and XPS-700. Quasi-static compressive properties of the same XPS foams as used in this study have been extensively investigated by Reyes and Børvik [6,7], and some of these results are repeated below for completeness. In this work, the strain-rate sensitivity of the XPS foams was further investigated through a series of low-velocity impact tests on cubic samples.…”

“…In series 2, the strain-rate sensitivity of the foams was examined by running tests on specimens in ND with an elevated crosshead velocity of 30 mm/min and 300 mm/min, respectively, corresponding to initial strain rates of 1 × 10 −2 s −1 and 1 × 10 −1 s −1 . The complete test matrix and nominal material parameters are given in [7].…”

“…The compressive response of the three XPS foams at elevated strain rates was investigated by conducting low-velocity impact tests in an Instron CEAST 9350 drop tower system (Instron, Norwood, MA, USA) using cubes with dimensions 50 mm × 50 mm × 50 mm as samples. The test setup was similar to that used by Reyes and Børvik [7], with some minor modifications to account for the test sample geometry. Here, a conical steel nose with a maximum diameter of 80 mm was attached to the instrumented striker to create a rigid, flat impact surface.…”

“…As the load cell is not located at the tip of the striker, the recorded force is not equal to the contact force between the impactor nose and the test sample. Based on dynamic equilibrium, the actual impact force (F) was found from the recorded force (P) according to Equation (1), accounting for the mass m 1 above and the mass m 2 below the load cell [7].…”

“…As the sheet and core can consist of a range of different materials, there have been numerous studies over the years on various types of sandwich panels depending on the load case. Recently, Reyes and Børvik [6] investigated the quasi-static behaviour of sandwich panels with steel skins and six different polymeric foam cores, while the same panels were examined under low-velocity impact loading in [7]. The main conclusion from these studies was that in order to minimise the weight and at the same time maximise the energy absorption of the sandwich panel, a low-density foam should be used as core material.…”