Impact perforation of sandwich panels with aluminum foam core: A numerical and analytical study

• Impact perforation of sandwich panels with aluminum foam core is investigated numerically and analytically.
• The proposed numerical model can predict piercing force vs. displacement curves in good agreement with experimental measurements (tests at impact velocities at 27 and 44 m/s).
• A continuous increase of the piercing force of top skin with impact velocity (up 200 m/s) is found.
• Shock front propagation is responsible for piercing force increase found under impact loading.
• An analytical model using an improved RPPL shock model based on a power law densification assumption is proposed to calculate the top skin piercing forces.

This paper tends to study the observed piercing force of sandwich panels with foam cores under impact loading by numerical and analytical methods. For this purpose, numerical models are built using LS-DYNA and calibrated with the inversed perforation test instrumented with an instrumented pressure bar on the AlSi7Mg0.5 Aluminum foam core sandwich panels with 0.8 mm thick 2024T3 Aluminum top and bottom skins. Actually, the proposed numerical model can predict piercing force vs. displacement curves in good agreement with experimental measurements (tests at impact velocities at 27 and 44 m/s). More confidence is obtained by the fact that the simulation can also reproduce the failure mode of the top skin and bottom skin.Virtual tests using this numerical model are conducted with higher impact velocities up 200 m/s. A continuous increase of the piercing force of top skin with impact velocity is found. A careful analysis of numerical results (difference between top and bottom skin perforation, stress level beneath the top skin, etc.) shows that the foam core strength enhancement due to shock front propagation is responsible for this piercing force increase under impact loading.Finally, an analytical model using an improved RPPL shock model based on a power law densification assumption is proposed to calculate the top skin piercing forces. This analytical model provides a prediction in good agreement with the experimental and FE results in a large range of impact velocities.