Hygothermal (environmental) effects in high-order bending of sandwich beams with a flexible core and a discontinuous skin

Abstract

Hygothermal (environmental) effects on the behavior of a sandwich beam with a ‘soft’ core i.e. flexible in the vertical direction, and a discontinuous skin using a high-order approach, are derived and presented. The hygothermal effects, such as thermal expansion, moisture swelling and shrinkage contraction, have been derived using a rigorous approach for the analysis of sandwich beams having high-order effects owing to the non-linear patterns of the inplane, and the vertical deformations of the core through its height. The sandwich beam construction is general and consists of two unidentical continuous or discontinuous skins and a ‘soft’ core. The discontinuity in one of the skins is in the form of thin gaps that extend through width, are denoted as skin-gaps or gap-wise skins, and are located at various locations. The formulation details the governing equations and the associated boundary conditions, along with the hygothermal effects, of a general sandwich beam or panel with continuous and discontinuous skins and the conditions at the location with gap-wise discontinuity. The analysis results throughout the entire length of the structure and at singular points, such as skin-gap tips, are described in terms of internal resultants and displacements of each skin, transversely normal stresses (peeling stresses) and shear stresses at the various skin-core interfaces, and stress and displacement fields in the core throughout its height. The stress concentration at gap tips in the form of finite peeling (transverse normal) and shear stresses at the skin-core interfaces are determined analytically and presented numerically. The hygothermal effects, that are significantly high in the vicinity of the gap and at support regions, have been studied numerically for beams with continuous and discontinuous skins. The effect of the distance between two consecutive gaps on the stress field at gap tips under thermal and shrinkage induced deformations are studied and conclusions are drawn. Moisture swelling of the core and its effects on the behavior of the beam in the case where the vertical edge displacement is prevented are presented. Verification is proved through comparison with the experimental results of a two-span sandwich beam that is supported at the lower skin only and subjected to a thermal gradient.