Numerical assessment of the core deformability effect on the behavior of sandwich beams

A modified zig-zag technical theory suitable for the accurate analysis of multi-layered composite beams accounting for the full 3D stress state has been recently developed by one of the authors [U. Icardi, A three-dimensional zig zag theory for analysis of thick laminated beams. In: Modern Trends in the Theory and Behavior of Structures Symposium ASME 1999 Summer Conference, Blacksburg, Virginia, USA, 27- 30 June 1999]. In order to satisfy the transverse shear and the transverse normal stress and stress gradient continuity requirements at the laminae interfaces through appropriate jumps in the strains, the theory features a piecewise third-order approximation for the in-plane displacement and a fourth-order approximation for the transverse displacement across the thickness. In the present paper, the capability of such a theory to predict the displacement and stress distribution across the thickness of sandwich beams is numerically assessed. This is done by comparing present estimates with the Pagano's elasticity solution [N.J. Pagano, J. Compos. Mater. 3 (1969) 398-411] for simply-supported, sandwich beams with cross-ply faces, loaded by a sinusoidally distributed transverse load. Additional results are presented that evidence the effects played by an enhanced core's deformability, or by stiffening the faces. It is seen from the numerical results presented the need for including non-classical complicating effects, to accurately predict the stress and displacement distributions across the thickness, and even for the estimation of the overall response. These comprise modeling of the transverse normal strain and transverse shear deformation; fulfillment of the transverse shear stress and transverse normal stress and stress gradient continuity conditions at interfaces; modeling of the cross-section warping. The numerical results show a good predictive capability of the present model with using one sublaminate for each layer and for the core, except for the case of faces with drastically different elastic moduli, which require use of more sublaminates. (C) 2001 Elsevier Science Ltd. All rights reserved.