Energy partition for ballistic penetration of sandwich panels

Ballistic impact and penetration in sandwich panels at projectile velocities above the ballistic limit are considered. An analytic model is developed that deals with partition of the energy of absorption, allowing for quantitative estimation of the energy fraction consumed via panel elastic response and the one consumed via irreversible damage. The analysis is based on simultaneous solution of two differential equations describing bending and shear deformation of a sandwich panel and taking into account the energy conservation. The solution technique includes the direct and inverse Hankel transformations and results in practical expressions for elastic response and damage energy fractions. Numerical results are corroborated with experimental data obtained from intermediate-velocity impact tests performed for sandwich panels with FRP composite laminate faces and foam cores.