A generalization of the refined zigzag theory (RZT) for the analysis of partially delaminated sandwich beams

Abstract

This work introduces an extension of the refined zigzag theory (RZT) for the analysis ofpartially delaminated beams. The primary objective is to propose an enrichment of thekinematics that enables adequate modeling of beams composed of two external rigidlayers and a flexible core (sandwich) in which partial delamination has occurred betweenthe core and one of the external rigid layers. The extension of the RZT involves animprovement in the interpolation of axial displacements in the core through the additionof three degrees of freedom. These include the displacement jump that appears in thedelaminated layer, as well as two additional variables associated with the curvature of thesection in the core and the concentration of displacements in the delaminated area. Theoriginal RZT has a limitation in the treatment of non-homogeneous beams, specificallywhen the mechanical properties of the layers change along the length of the beam (asoccurs in partial delamination), leading to a non-conforming approximation. The modelproposed in this article is conforming and allows for a highly efficient approximation of theoverall behavior of sandwich beams, including their stiffness characteristics and thediscontinuity in the delaminated layer, while also improving the prediction of transverseshear stresses. Two examples are presented and discussed to demonstrate the effectivenessof the proposed approach.