Non-linear behaviour of foams under static and impact three point bending

The influence of impregnation on mechanical properties of polyurethane foams at room temperature has been experimentally evaluated in both static and impact loading conditions. The impregnation layer increases the flexural modulus and changes the foam behaviour at impact. For un-impregnated foam the energy absorbed to fracture is equal to the impact energy, while for the impregnated specimens the energy absorbed to fracture is approximately 80% of the impact energy, which indicated that the other part of the impact energy was consumed for internal damage. The same amount of energy was reached for both static and impact tests, but different shapes of energy versus displacement curves were obtained. For notched specimens under impact load, the effect of impregnation is cancelled and identical behaviour was obtained for un-impregnated and impregnated specimens.