Abstract: Lightweight and high-performance armor is essential for improving the ballistic protection of modern vehicles. Ceramic-ball/metal composite armors have emerged as a promising alternative due to their high hardness, efficient energy dissipation, and superior multi-hit potential; however, most existing studies focus on uniformly distributed ceramic balls and single-impact scenarios, leaving the damage evolution and protective mechanisms of gradient ceramic-ball composites under multiple impacts insufficiently understood. To address these limitations, this study investigates the ballistic performance of gradient ceramic-ball aluminum composite armor subjected to 12.7 mm armor-piercing incendiary projectiles through a combined experimental and numerical approach. Ballistic penetration experiments were conducted at different impact velocities, and validated finite element models were developed in LS-DYNA using the Johnson-Cook and Johnson-Holmquist constitutive models to analyze penetration depth, damage morphology, energy absorption, and projectile deflection under varying ceramic ball sizes, impact locations, impact spacing, and gradient arrangement directions./t/nThe results demonstrate that increasing ceramic ball diameter significantly enlarges the damage zone and intensifies structural non-uniformity, leading to greater sensitivity to impact point location. Under double-hit conditions, damage induced by the first projectile substantially weakens the energy absorption capacity of the composite target and alters the penetration behavior of the second projectile, especially when the subsequent impact occurs within the pre-damaged region. For certain impact spacings, projectile deflection triggered by non-uniform damage can reduce the penetration depth into the backing plate despite comparable energy absorption. Comparative analyses further reveal that positive-gradient ceramic-ball configurations, with smaller ceramic balls arranged on the strike face, effectively reduce the initial damage area by approximately 14.8% to 57.8% and maintain higher structural integrity under repeated impacts than negative-gradient designs.