Testing of polymeric foams at high and medium strain rates

International audienceExperimental data of the behaviour of polymeric foams at high and medium strain rates is required in the crash simulations developed in the automotive industry. This paper presents an investigation of particular difficulties in the testing of polymeric foams, using a Split Hopkinson Pressure Bar (SHPB). On the one hand, viscoelastic bars are used to improve the impedance ratio between the bar and the specimen and consequently the accuracy of measurements. A generalised two-gauge method is used to extend this measurement to the complete range of strain (up to 80% of nominal strain), and allows also for performing tests at medium strain rates (5–50 s−1). On the other hand, the assumption of the homogeneity of the strain and stress fields in the specimen is studied, using a high speed photographic system