Failure of an impulsively-loaed composite steel/polymer plate

The concept of spraying a thick layer of a polymeric material onto a metal plate has recently received considerable interest in many civilian and military applications. There are numerous analytical and numerical solutions for single thin (membrane) plates made of either a steel or an elastomer. However, solutions for a composite plate made of both of the above constituents are lacking. The objective of the present paper is to formulate a model for a composite steel/elastomer plate, derive an analytical solution for the plate subjected to impulsive loading and compare it with a more exact numerical solution. It is assumed that the circular plate is fully clamped around its periphery, and it is loaded by a uniformly distributed transverse pressure of high intensity and short duration. The pressure imparts an initial impulse which is proportional to the initial transverse velocity of the plate. As an example, DH-36 is used for a steel backing plate while polyurea is chosen as a coating. The analytical model is developed where the steel layer is treated as a rigid perfectly-plastic material. The magnitude of flow stress is adjusted iteratively according to the calculated magnitude of average strain. On the other hand, a linear elastic material is assumed for the polyurea with elastic modulus in the tensile range calculated from the Arruda-Boyce model. The magnitude of the average strain rate was relatively low, about 100 sec^-1; therefore, the effect of strain rate is not considered in this paper. A comprehensive parametric study was performed by varying several material and structural parameters in the model. A closed-form analytical solution was compared with the results of detailed FE simulations of composite plates, and good correlation is obtained. It was found that the polyurea coating could improve the failure resistance of the composite plate by 20% provided that the thickness of the coating is 5-10 times larger than the plate.