EVALUATION OF COLLISIONAL DAMAGE IN POLYSTYRENE FOAM CONSTRUCTIONS USING A DUAL HAMMER IMPACT TEST

Low intensity impacts can reduce the structural integrity of an expand ed polystyrene safety helmet by the formation of damage in the foam. T his reduces the ability of the foam to protect the user under impact c onditions. In these experiments, the introduction of a rubber inter-la yer that acts as a cushioning layer to protect the polystyrene shell d uring light and intermediate impacts was evaluated. The evaluation was conducted with a dual hammer impact tester, which was constructed for this purpose. Safety helmet cross sections were simulated by two inch square test specimens. The dual hammer impact testing identified a da mage threshold energy above which damage was evident. The introduction of the soft rubber inter-layer between the foam and outer hard shell of these specimens increased the impact loading required to damage the foam by 30%, while the amount of energy transmitted actually increase d. Further work is being done on perforated rubber systems that will l ook at damage and energy transmission in these alternative constructio ns.