HYGOTHERMAL (ENVIRONMENTAL) EFFECTS IN HIGH-ORDER BENDING OF SANDWICHBEAMS WITH A FLEXIBLE CORE AND A DISCONTINUOUS SKIN

Hygothermal (environmental) effects on the behavior of a sandwich beam with a 'soft' core, i.e. flexible in the vertical direction, and a di scontinuous skin using a high-order approach, are derived and presente d. The hygothermal effects, such as thermal expansion, moisture swelli ng and shrinkage contraction, have been derived using a rigorous appro ach for the analysis of sandwich beams having high-order effects owing to the nonlinear patterns of the inplane, and the vertical deformatio ns of the core through its height. The sandwich beam construction is g eneral and consists of two unidentical continuous or discontinuous ski ns 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 formulati on details the governing equations and the associated boundary conditi ons, along with the hygothermal effects, of a general sandwich beam or panel with continuous and discontinuous skins and the conditions at t he location with gap-wise discontinuity. The analysis results througho ut the entire length of the structure and at singular points, such as skin-gap tips, are described in terms of internal resultants and displ acements of each skin, transversely normal stresses (peeling stresses) and shear stresses at the various skin-core interfaces, and stress an d displacement fields in the core throughout its height. The stress co ncentration at gap tips in the form of finite peeling (transverse norm al) and shear stresses at the skin-core interfaces are determined anal ytically 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 discontinu ous skins. The effect of the distance between two consecutive gaps on the stress field at gap tips under thermal and shrinkage induced defor mations are studied and conclusions are drawn. Moisture swelling of th e core and its effects on the behavior of the beam in the case where t he vertical edge displacement is prevented are presented. Verification is proved through comparison with the experimental results of a two-s pan sandwich beam that is supported at the lower skin only and subject ed to a thermal gradient. (C) 1997 Elsevier Science Ltd.