Forward and inverse analysis for impact on sandwich panels

A Green's function approach is presented for forward and inverse analyses of sandwich panels that were struck transversely at low velocities. To model the dynamic response of the panel, both membrane and bending deformations of the laminated face plates were considered, and the core, in this case made of honeycomb, was treated to deform by transverse shear force. The displacement field of the panel as a whole was then modeled using beam functions along with the Rayleigh-Ritz method. The derived coupled equations of motion were further transferred to the eigenspace to form Green's function. In the forward analysis, the solution was obtained directly, and the agreement between the prediction and the measured data was found to be very satisfactory when the impact location was beyond a distance that was a few times the panel thickness. On the other hand, a constrained optimization method was employed in the inverse analysis to search for the optimal impact force history from the recorded strain histories. The determined force history was also found to have a very satisfactory agreement with the measured one.