Modeling and Simulation of a Shock Absorbing Shell for Ballistic Vests and Helmets to Achieve Optimal Protection

This work deals with the modeling and simulation of shock absorbing shells for ballistic vests and helmets to achieve optimal protection. Shock absorbing shell is modeled as a circular membrane with clamped edge. Symmetrical loading patterns were considered as follows: uniformly distributed pressure over the entire surface of the shell, uniformly distributed pressure over a part of the shell´s surface, for bullets with button and truncated cone nose, as well as centric concentrated force, for bullets with conical and tangential ogive nose. Depth and volume of the back face signature, as well as the shell stiffness were evaluated. Then, the influence of force eccentricity was considered. Ballistic vests and helmets offer the lowest degree of protection for loading by concentrated centric forces, since they produce the largest back face signatures. Increased protection is achieved if the bullet contacts the shell unit at a certain eccentricity, and if the bullet´s impact force is spread over a larger area. Based on such models one explains the experimentally observed armor strengthening by silica colloidal pads placed on the outer or inner face of the shell unit.