MECHANICAL-PROPERTIES OF POLYURETHANE-FOAM IMPACT LIMITERS

Rigid, closed-cell, polyurethane foams possess excellent energy-absorb ing properties and are used as impact limiters for various packaging a pplications. They can absorb large quantities of energy as they transm it a stress equal to their crushing strength. Recently, their mechanic al properties have come under increased scrutiny due to applications i n nuclear-waste shipment packages. In such an application, the materia l is subjected to multiaxial state of stress. Strain-rate effects due to the dynamic nature of the loading in an hypothetical accident situa tion is also likely to be encountered. This paper describes a number o f tests performed on polyurethane foams of various densities along sev eral loading paths. These include uniaxial, hydrostatic and triaxial c ompression. Strain-rate effects were also studied under compressive lo ading. Since the material is significantly anisotropic, the experiment al data are used to infer elasticity parameters and the shape of the a nisotropic yield surface. Some strain-rate effects are also examined.