An empirical model to estimate the ballistic velocity limit (BLV) of bi-layer ceramic–metal armor materials, considering momentum and energy balance during impact process, is proposed. Three ceramic materials as front layer, namely: alumina (Al2O3 96%) boron carbide (B4C) and silicon carbide (SiC) and three materials as backing layer, namely: aluminium alloy (Al 5083H116), steel 4340 and titanium alloy (Ti6Al4V), are considered. Initially, materials constitutive and failure model constants are validated through comparison of simulations performed using finite element explicit solver, AUTODYN®, against the available experimental data in the literature. Impact simulations of different combinations of thicknesses and materials from three ceramic materials and three metal materials and thicknesses and different projectile lengths, chosen based on orthogonal array technique, are performed from which B LV of the armors are calculated. Empirical constants in the proposed model are obtained using least square fitting to the B LV data obtained from simulations. Comparison between results obtained from the empirical model for B LV of ceramic–metal armor impacted by flat-ended projectiles, with available limited experimental data is carried out. The empirical B LV expression is used for optimization of alumina/aluminium armor system, for weight and volume objectives. Optimization results compare well with the experimental measurements.

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In this paper, the effect of integration of natural fibers in UD carbon fiber is studied. The integration of natural fibers in carbon fiber is made via intra fiber hybridization. Natural fiber hybrid composite samples were prepared for Mode I and Mode II fracture tests. XRD analysis was done for the chosen natural fibres to know the crystallinity index and then compared with Carbon and Glass fibres. The fracture test experimental results, revealed that the effect of Jute fiber integration in UD Carbon epoxy composite was found significant in getting relatively good Mode I and II fracture toughness at the crack initiation without losing its stiffness. In addition to this Kenaf Carbon epoxy composite indicated better crack suppression with 30% higher propagation toughness values as compared other hybrid combinations and pristine composites. It is observed that integration of jute fibers in UD carbon epoxy composites was significant in achieving good mode I and mode II fracture toughness at the crack initiation without losing its stiffness and also kenaf carbon epoxy composites indicated better crack suppression with 30% higher propagation toughness as compared to other hybrid combinations used.