Abstract <p>Based on previous research on the anti-penetration performance of steel-aluminum composite structures conducted by our research group, in order to reveal the influence mechanism of the angle of incidence and the coupling relationship between fragment geometry and initial velocity, simulations of oblique penetration on single target plates with different fragments and initial velocities were carried out using an established numerical model. Starting from vertical penetration, it was discovered that for target plates of the same material and thickness, a larger angle of incidence results in a greater change in the projectile’s angle. Protection is more effective when the target plate is inclined at ≤30° or the angle of incidence is ≥60°. For composite target plates with a surface density of 5 g/cm³ and a thickness ratio of 0.305, when the angle of incidence exceeds 50°, the percentage of energy dissipation for both sphere and cube fragments decreases as the angle increases, with cube fragments dissipating more energy. Empirical formulas for the residual velocity of cube and sphere fragments at thickness ratios of 0.305, within angle ranges of 0°–20° and 50°–80°, were derived. These findings can provide references for protection design against penetration by fragments with high angles of incidence and low initial velocities.</p>