Compressive response of polymeric foams under quasi-static, medium and high strain rate conditions

Polymeric foam materials are widely used for impact protection and energy absorption, for which advanced design and modeling requires appropriate material characterization data and constitutive models. The compressive mechanical behavior of three common polymeric foams (expanded polystyrene, high-density polyethylene, and polyurethane) has been measured at strain rates ranging from 0.0087 to 2500/s. Although a large amount of compression data is available in the literature, most of this data only addresses strain rates up to 250/s, with higher rate data limited to modest levels of compression. This represents a significant deficit in the current knowledge since many applications are leading to the use of foams at high rates and significant total deformation. The material characterization was accomplished using a standard compression test device and a drop tower apparatus to achieve rates up to 100/s. A polymeric split Hopkinson pressure bar apparatus was used to achieve strain rates from 500 to 2500/s. This data has been used to investigate a common foam constitutive model, and shows that strain rate effects become more pronounced at rates above approximately 1000/s.