Angle-dependent shielding performance of Ti-6Al-4V/AISI 1045 bilayer panel under hypervelocity impact

Hypervelocity ballistic impacts are becoming common with scientific advancements in propulsion technology. Space collisions like meteoroids also involve high-velocity impacts. Traditional metallic sheets like Ti-6Al-4V and AISI 1045 steel, when employed in thin configurations, exhibit limited capacity to endure the severe stresses generated during high-speed impact events. In this paper, the response of a Ti-6Al-4V titanium alloy and AISI 1045 steel bilayer panel to a hypervelocity aluminum ball impact was studied to observe the underlying phenomenon of spalling, cavitation, and debris-cloud formation caused by such hypervelocity impacts. Using the Modified Johnson–Cook material model along with the Grüneisen equation of state to represent the impacted materials and implementing the smoothed particle hydrodynamics approach within the commercially available finite-element software LS-DYNA, the penetration behavior under symmetric and asymmetric impact conditions was investigated. Results demonstrated that impact angle, after the critical threshold of 30°, strongly influenced the energy distribution, flow stress, and the rear-face bulge formation of the lower AISI 1045 steel plate. These findings provide practical design guidance for optimizing multi-layer metallic shielding and impact-resistant structures against hypervelocity debris.