In this paper, the penetration behavior of newly designed sandwich structures consist of a 6061-T6 Al alloy sheet and two-layered plain-woven E-glass/epoxy composite laminates and syntactic foam core is investigated experimentally and numerically. Penetration tests are conducted using a single-stage gas-gun and steel conical-ended projectiles to evaluate the accuracy of the finite element model. The 3D finite element code, ABAQUS/Explicit, is used to model the penetration behavior of the sandwich structures. The Johnson-Cook models for material and damage behaviors are used to model the behavior of aluminum sheets. The progressive damage model based on the generalizations of the Hashin failure criteria in a VUMAT subroutine, and the crushable foam model associated with the Reyes fracture criterion in a VUMAT subroutine are employed to simulate the behavior of composite laminates, and syntactic foam, respectively. To validate the finite element model, the penetration behavior of sandwich structures is compared with the experimental results obtained from the experimental study and has shown accurate predictions. The suggested finite element model can predict the residual velocity and perforation energy with 11.2 % and 2.6 % errors, respectively. The effect of foam core thickness, fiber-metal laminate thickness, and impact velocity on the penetration behavior of sandwich structures is studied using the confirmed finite element model. It is observed that the failure of the sandwich structures mainly happens in the impacted area. Also, it is concluded that the effect of the Al thickness on the penetration resistance is more significant than foam and composite thicknesses. Furthermore, as the impact velocity is increased, the penetration time and loss of the velocity are decreased and the perforation energy is increased.
