“Segment-wise model” for theoretical simulation of barely visible indentation damage in composite sandwich beams: Part I – Formulation

When localized transverse loading is applied to a sandwich structure, the facesheet locally deflects and the core crushes. A residual dent induced by the core crushing significantly degrades the mechanical properties of the sandwich structure. The authors establish a “segment-wise model” for theoretical simulation of static indentation loading and unloading responses in honeycomb sandwich beams with composite facesheets. The model was developed by modifying a theory developed for an Euler beam on an elastic Winkler foundation. The honeycomb sandwich beam was divided into many segments based on the periodic shape of the honeycomb, and the complicated through-thickness behavior of the core was integrated into each segment. First, compressive stress–strain curves were measured during the crushing–stretching process of the core using uniaxial flatwise compressive-tensile tests. Using the through-thickness properties approximated as a set of lines, the 2D indentation response in an aluminum honeycomb sandwich beam was then theoretically simulated. The obtained load–displacement curve was validated by an experiment, confirming the superiority of the new model over a conventional elastic-perfectly plastic model. Further experiment verification and a discussion are presented in Part II of this study.