The phenomenon of face wrinkling is a local face sheet buckling that occurs in sandwich structures subjected to in-plane compressive and shear loads. It has been identified as one of the major failure modes and was first investigated with the core modeled using a Winkler-type elastic foundation [1]. The face wrinkling mode is characterized by a much shorter wavelength compared to the general global buckling of the panel. The wrinkling may be either symmetric (out of phase) or antisymmetric (in phase) with respect to the midplane of the sandwich panel. Three major wrinkling models for the core have been developed in the early research work of face wrinkling analysis - a Winkler elastic foundation model (Gough et al. [1]), a linear decaying model (Hoff and Mautner [2]) and an exponential decaying model (Plantema [3]). Predetermined shapes for both symmetric and antisymmetric wrinkling have been assumed in their analysis. The agreement between the theoretical and the experimental wrinkling stresses was reasonable. The wrinkling problems based on pre-assumed shapes for wrinkling mode was described in the monographs [3-6]. Birman and Bert [7] studied the face wrinkling under biaxial loading using these three models. Vonach and Rammerstorfer [8] investigated the wrinkling of orthotropic sandwich panels under general loadings. Hadi and Matthews [9] expanded the Benson-Mayers theory [10] for isotropic sandwich panels into general anisotropic sandwich panels.
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