Stress concentration in bending of sandwich orthotropic panels under point forces

Analytic expressions for flexural characteristics and stresses of sandwich panels under loading by point forces with taking into account local effects have been found. A refined discrete-layer model for bending of a three-layer panel that is composed of orthotropic face layers and intermediate middle layer with low rigidity of the latter is proposed. The outer layer made of composite material and high rigidity not so much in tension and shear in the transverse direction as in longitudinal direction characterize it. Contractility of a normal in the model is deduced in terms of a difference between deflections of face layers. Equations of the model, having four degrees of displacement freedom are of 12th order. The specific features of the stress from point forces in cylindrical bending are considered using the operational Laplace method with the generalized Dirac function. The boundary problem of a panel supported along the surface of its lower face layer with free ends is reduced to the Cauchy problem. Variants are examined for the limiting transformation of the model parameters leading to a qualitative change in its kinematics and the corresponding simplified bending models. (C) 1999 Elsevier Science Ltd. All rights reserved.