Effect of varied alumina/zirconia content on ballistic performance of a functionally graded material

Functionally graded materials (FGMs) are characterized by continuous variation in their composition and structure with thickness or volume. Hence, the corresponding changes in the properties and functions of the FGMs can be investigated to create new materials. In this study, four-layered FGM specimens with three different compositions, i.e., Al2O3/(0, 5, 10, 15%) ZrO2, Al2O3/(0, 10, 20, 30%) ZrO2 and Al2O3/(0, 15, 30, 45%) ZrO2, were designed. The ceramic specimens were hexagons whose sides were 11 mm long. Accordingly, 6061-T6 Al was used as a back plate. A ballistic test was conducted using 0.3″ armor-piercing bullets with an initial speed of 868 ± 15 m/s. Numerical simulation software, i.e., LS-DYNA, was employed to analyze stress transfer and the fracture of the FGM specimens under impact. The ballistic test showed that the Al2O3/(0, 5, 10, 15%) ZrO2 FGM exhibited the best impact resistance performance. The investigation of microstructures through observation using a SEM did not show delamination in the FGM interlayer after impact. Furthermore, the abrasion between the ceramic and projectile increased. XRD analysis verified the phase transformation of ZrO2 from the tetragonal phase to the monoclinic phase. This transition delayed crack growth and increased material toughness, thereby promoting the impact resistance performance of the FGMs.