Assessment of Effective Elastic Properties of Honeycomb Cores by Modal Finite Element Analyses

摘要

The main issue in analyzing honeycomb structures is the substantial computational effort that has to be spent in modeling and analyzing them with a multi-cell construction core by maintaining the actual geometry. Therefore, the common practice in the finite element modeling is to replace them by an equivalent orthotropic material. The determinations of these equivalent properties of the homogenized core are based on analytical or numerical relationships usually obtained from pure axial and shearing loads. By using these initial estimations of the equivalent properties, a homogenized model works well for in-plane deformations but may give large errors for out-of plane deformations which generally take place in panel or sandwich homogenized structures. This paper presents a numerical method that can be used to correct some of the equivalent elastic properties of the homogenized core to work properly in bending and torsion based on some modal analyses applied first for a real honeycomb panel, to obtain a reference solution, and then on the homogenized orthotropic panel where some of the equivalent elastic constant are iteratively improved by an optimization algorithm to fit the reference solution. The analyzed types of honeycomb cores are the commercial ones in three cell configurations: square, regular hexagonal and re-entrant shapes. The calculations show that some of the equivalent elastic properties obtained in the classical approach must be corrected with factors larger than five as to obtain correct results in bending and torsion loads.