Flexural Wrinkling in Foam-Filled Sandwich Panels

The ultimate flexural buckling failure of foam-filled sandwich panels with light gage cold formed metal faces is preceded by wrinkling of the compression face. A rational theory is presented for predicting the critical wrinkling stress from the properties of the core and faces. Five types of panels with three face configurations and four kinds of rigid urethane foam were subjected to center point loading. Critical wrinkling stresses were observed where there was a deviation in the initial linear load/strain relationship. The experimental critical stresses were compared to those derived from a mathematical analysis, wherein the compressed face is considered as a beam supported by the continuous elastic medium of the core and the tension face. A family of curves is presented for computing critical stresses for the face and core properties.