An investigation of SDOF models for large mass impact on sandwich composites

This paper describes an investigation of single-degree-of-freedom models for large mass impact on composite sandwich laminates. The stiffness parameters of the models are derived from the results of three-dimensional quasi-static contact analyses of a rigid sphere indenting a multi-layer sandwich laminate. Energy dissipating elements are incorporated into the models to account for material damage. The validity of the models is examined through comparisons with experimental force history results of impact on six different core and face sheet configurations. It is found that a Maxwell element with the nonlinear spring in series with a viscous damper element best models the impact phenomenon for this boundary condition controlled impact. The damping parameters for each type of laminate analyzed, although initially determined empirically, are found to have a unique relationship to the energy dissipated at the time of maximum contact force. With this relationship known, the damping parameter can be determined a priori to accurately predict the peak contact force and contact duration for these foam and honeycomb sandwich panels.