Closed form prediction of peak load and delamination onset under small mass impact

Small mass impact on plates is a common response type caused by hailstones and runway debris. The response in such cases is wave controlled and the load and deflection are out of phase and independent of plate size and boundary conditions. Previous solutions to the problem have been based on laborious numerical approaches not suitable for design. This paper presents a closed form solution based on three asymptotic cases with deformation purely by indentation, bending or shear. Solutions are presented for a Hertzian contact law, suitable for monolithic plates, and for a linear contact law, suitable for sandwich panels. A good agreement is shown with “exact” numerical solutions and experimental results. The solution is also combined with an existing quasi-static delamination threshold load criterion. Comparison with several published experiments indicates that the criterion also may be applicable to small mass impacts.