A general model to describe the compression impact behavior of cellular materials

Abstract

Cellular materials, commonly known as foams, are largely used for packaging and for the mitigation of the consequences of the impact of vehicles, for their ability to absorb the impact energy while maintaining the loads under critical values. The design of energy absorption systems and devices like car bumpers, road barriers and protections, helmets, packaging, it is useful to have mechanical models of the cellular materials with a higher level of predictability. Such models must describe the stress-strain response in the uniaxial compression first, as well as the tension and multiaxial loading; additionally, influencing factors as strain-rate, temperature, and density must be accounted for. This could help the designer in selecting optimal solutions to minimize weight for a given amount of energy to be dissipated.

In 2005 the authors presented a model of the stress-strain behavior of some polymeric based foam materials, in quasi-static loading. The model was further improved and a complete description of the stress-strain behavior of some metal-based cellular materials including the influence of strain-rate and foam properties was published.

In this paper, that model is applied to some polymeric based cellular materials. Among the considered materials, there are expanded polypropylene (EPP), expanded rigid polyurethane (PUR), expanded polystyrene (EPS). The work will give a review of the identified parameters for each family of materials, drawing the attention on the peculiarity of each of them. The parameters have been identified from previous experimental data from the same authors. Such tests consisted of quasi-static, and impact tests, at various loading/impact speed and energy.

The paper will try to show suitability of the proposed model for most cellular materials in compression, possibly any cellular expanded material, to be considered a valuable tool for design in the safety and packaging applications.