Softness measurements for open-cell foam materials and human soft tissue

In this paper, methods of measuring the softness of open-cell polyurethane foams in terms of their Young's modulus using indentation methods are investigated and shown to be in agreement with values determined by normal compression tests. The comparison involved the use of a formula relating Young's modulus for elastomers to the axial indentation forces on a cylindrical probe. This had been developed for cartilage and verified for other biological tissues and could not automatically be assumed to be valid for an open-cell structure. An indentation method was then used to characterize the soft tissues of the female human body, averaging over several locations on the body and for several volunteers. It is concluded that the mechanical characteristics of foams can be measured in a repeatable manner by the indentation method and that appropriate foams can therefore be selected for use in a soft mannequin which will then accurately simulate the texture and mechanical behaviour of human soft tissue.