Comparison Between Different Cellular Cores and Finite Element Modeling Techniques

omparison among the equivalent-continuum (homogeneous) constitutive law for Hexagonal, square and triangular cores to be used in sandwich panels is presented. The cellular core homogeneous properties are calculated using detailed finite element models of representative unit cell for each core shape. A strain energy based homogenization scheme that was first presented by Hohe and is based on the concept that for every cellular material, there exists a homogeneous material that is of the same shape and behaves identically to the cellular structure when it is subject to the same loading and boundary conditions is also be used to calculate the constitutive law for the same core shapes and the same core densities. A detailed comparison between the homogenized constitutive law obtained using the detailed finite element models and that obtained using Hohe’s approach is presented herein. The strain energy based homogenization scheme was previously verified by Soliman et. al. [1] for a non-corrugated square shape core. In this paper, the hexagonal and square core shapes are made of corrugated Aluminum 5056 sheets. The variation of the mechanical behavior of the homogeneous structure equivalent to the cellular core with respect to the relative density and cell size of the cellular core is analyzed and equations for direct calculation of the constitutive behavior of the three types of cellular core is presented. Additionally, different finite element modeling techniques of the cellular cores within a 10”× 10” panel with simply supported boundary condition is also presented. The finite element modeling techniques presented are: a) detailed modeling of the cellular core within a sandwich panel, b) 2D modeling of the equivalent continuum within a sandwich panel using the MAT8 NASTRAN ® card to represent the core homogenized material , and c) 3D modeling of the equivalent continuum within a sandwich panel using the MAT9 NASTRAN ® card to represent the core homogenized material. The modeling techniques will be compared in terms of the displacement field of sandwich panels consisting of the different types of cellular core and subject to uniform pressure.