Shock enhancement effect of lightweight composite structures and materials

Polymeric foams, textile materials and metallic foams are commonly used lightweight composite structures and materials for personal protective equipment (PPE) and protective structures in the battle field, because of their capabilities in reducing the risk of damages against ballistic impact. Under blast loading, however, a "shock enhancement" phenomenon has been observed in these materials, that is, the transmitted pressure is amplified, rather than attenuated as one would expect. Experimental evidences also demonstrated that covering animals with a layer of foam or textile could markedly increase the severity of lung injury. A number of studies have been published documenting such counter-intuitive effect. This review attempts to compile the state-of-arts and latest advances in this important subject. Experimental investigations on the pressure amplification of the aforementioned materials are summarized. Analytical/computational models that describe this phenomenon, particularly emphasizing on the mechanism and some key parameters affecting shock enhancement behavior, are also included. Finally, limitations of studies reviewed herein are discussed and issues which need to be addressed in further research are highlighted. (C) 2011 Elsevier Ltd. All rights reserved.