Investigation of shock wave attenuation in porous materials

This thesis investigates the use of porous materials in a multi-layered armor concept. The prototype layered structure consists of an initial high-strength material to slow down the projectile and cause significant plastic deformation,, followed by an orthotropic wave-spreading layer to spread shock waves laterally away from the axis of penetration and subsequently attenuate the shock waves by using a porous material to convert kinetic energy into internal energy. Based on the above armor concept, composite plates consisted of an alumina (Al203)-based ceramic, Dyneema® and porous foams were constructed and tested against conventional armor steel of equivalent areal density. This study used two commercially available porous materials, one based on aluminum metal and one a rigid polyurethane foam. This study also investigated the effect of porous initial density of the polymeric foam on ballistic. The author developed a P-a compaction model for the chosen porous materials for use in AUTODYN® simulations to describe their dynamic compaction during an impact event. The author also conducted a ballistic trial to validate the performance of the armor laminate against numerical simulations. Based on the results of this study, the porous layer has proven to be a good shock attenuator. The porous material efficiently delays the shock wave propagation and attenuates the amplitude by absorbing the kinetic energy through compaction of the material. The current research has also proven that the material layering sequence is fundamentally correct and has its merits.http://archive.org/details/investigationofs109454386Singapore Technologies Dynamics, Ltd. author (civilian).Approved for public release; distribution is unlimited