The paper analyses the mechanical performance of a novel cellular structure, proposed as core in sandwich panels. The reason for creating such a topology is discussed and a comparison is drawn between the macro-mechanical properties of a sandwich beam containing the novel core and the most known cellular topologies - honeycomb, corrugated and pyramidal lattice truss - investigated in the same loading conditions. The variations of the mechanical properties in terms of the geometrical parameters are numerically determined for each type of cellular cores and their structural performance is assessed in terms of the relative density and the mechanical characteristics of the base material. It is shown that for certain particular geometric characteristics, the proposed cellular core may be an alternative offering comparable bending and shear stiffness of the sandwich panel while keeping its weight very low.

This work presents the research results regarding the ballistic response characteristics of monolithic ceramic armors. Two different configurations of armors are considered for investigation, aiming at identifying ways to increase the ballistic performance of Small Arms Protective Insert (SAPI). The first configuration consists of a monolithic ceramic tile (Al₂O₃) with a backing plate made of high-performance Kevlar-29 fiber reinforced composite; the second one has the same design as the first, but the monolithic ceramic tile is covered by a thin rubber layer. The impact behavior of the ceramic composite armors is analyzed numerically, using the finite element method. Some characteristic features, including the ballistic performance and the fracture conoid angle (for the ceramic tile) are discussed. The numerical models developed for the two armor configurations are validated by ballistic tests, where the projectile impact on the armors and the mechanical integrity of the armor systems after impact are observed. The results from simulations and experiments show that the Al₂O₃/Kevlar 29 composite armor is able to capture a 7.62 mm bullet with a striking velocity of 690 m/s and the rubber-ceramic composite armor is able to capture 5.56 × 45 mm bullet M855 (with an armor piercing tip) with an impact velocity of 894 m/s. It has been found that, when a rubber layer is placed on the front face of a ceramic composite armor, better ballistic performance is achieved. The experiments show that, when a rubber material is impacted by a projectile, its behavior at high velocities and high strain rates changes from elastic to brittle.