Shock Mitigation Foams – The Basic Parameters

The development of shock absorbing polymer foams requires an appreciation of the complex phenomena involved. Isolation of the main parameters controlling shock mitigating potential is the essential prerequisite to any programme of research, and this paper outlines some of the problems involved. Comment is made on the matrix and structure of foam materials along with a brief survey of the mechanisms of energy dissipation that can operate during impact conditions. Methods of testing are discussed and essential differences between swinging pendulum, free fall and load/compression tests outlined. The role of density/property relationships is highlighted and emphasis given to the importance of incorporating appropriate material factors controlling stiffness, strain dependence and strain rate dependence into any equations used to predict depth of penetration and maximum deceleration of an impacting object.