Rigidity characterisation of flexible foams by falling dart rebound tests

Low-energy instrumented falling dart impact techniques have been applied to characterise the rigidity of several series of polyolefinic flexible foams , at relatively high strain rates. Rebound tests were specially designed in order to determine the elastic modulus of the foams by application of a th eoretical model that describes the indentation phenomena of a hemispherical element on a sample. A potential relationship between values of the determ ined elastic modulus and foam density was found and, as expected, the foams based in HDPE: showed the higher values of the elastic modulus of all the studied foams, whereas the samples containing EVA resulted in the lower val ues. Moreover, the elastic modulus determined using hemispherical dart head stocks (indenters) with different diameter resulted in a constant value, as the indentation model applied establishes. The results presented in this p aper show the utility of this test to characterise mechanically flexible fo ams, because it is sensible to identify small differences of rigidity due t o variable density, foaming process and chemical composition.