Core crushing and large face sheet deflections are incorporated in a theory for contact indentation of sandwich panels. The model is based on the assumption of axisymmetric indentation of an infinite elastic face sheet bonded to an elastic-ideally plastic core on a rigid foundation. After core yielding the problem is separated into an outer region where the core is elastic and an inner region where the core exerts a constant reactive pressure on the face sheet. The outer region is modeled as a plate on an elastic foundation. The inner region is modeled using small deflection plate theory, first order large deflection plate theory and membrane theory. The unknown plastic radius is found by matching the boundary conditions for the two regions. The extension of the model to orthotropic face sheets is indicated and demonstrated by an example. the predictions are in close agreement with experiments which contrasts to previously published models where membrane effects and core crushing were neglected. The model can be used for improved modeling of impact on sandwich panels.
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