Influence of constraints on the effective inplane extensional properties of honeycomb core

This study is focused on the influence of constraints on the extensional in-plane modulus of isolated honeycomb core (HC) and honeycomb core sandwich elements. Such constraints develop when the core is bonded to stiff face sheets. Finite element analysis (FEA) is conducted on unconstrained and constrained HC core under inplane loading. FEA results for the extensional in-plane modulus and Poisson ratios of isolated unconstrained HC core are in good agreement with estimates from the classical Gibson-Ashby analysis. Such analysis reveals that the isolated core has very low extensional modulus ( E x ) and large Poisson ratio ν x y . Constraints imposed on the lateral deformation of the core substantially increased the effective axial stiffness. In the limit of equal biaxial strains, the increase was close to a factor of 1000. The FEA results for the effective modulus of the HC core sandwich element are in good agreement with predictions from classical laminated plate theory.