Investigation on the ballistic performance of functionally graded boron carbide reinforced AA7075 matrix composites against 7,62 mm armour piercing projectiles

Composite materials are widely used in last decades for their more advantegeous properties than conventional materials. Functionally Graded Material is a new type of material and have potential in ballistic applications. In this study, three-layer FGMs were produced with three different thicknesses (15, 20, 25mm) by hot pressing and liquid phase sintering methods. Totally, 36 specimens were produced. The top, middle and bottom layers of these materials consist of 20% or 40% B4C reinforced composite, 10% or 20% B4C reinforced composite and 7075 aluminium alloy, respectively. Artificial aging process was applied to specimens at 100C, 120C and 150C up to 96 hours. Ballistic performances of these FGMs were investigated experimentally against 7,62mm armour piercing projectiles. Three point bending test were also applied to materials and materials investigated optically at macro and micro scale before ballistic tests. Artificial aging was applied to all of ballistic test specimens and some of three point bending test specimens at 120C and up to 48 hours. Other specimens were only solutionized and quenched. According to the experimental results, it was observed that reinforcements were distributed homogeneously in matrix material but it was also noticed that with the increase of reinforcement ratio in structure, some agglomeration was observed. Any of FGMs have not provide the ballistic protection. But as the increase in the thickness of material and ratio of the B4C, FGMs showed better performance ballistically. As a result of three-point bending tests it was observed that artifially aged specimens with low reinforcement ratio have highest transverse rupture strength.