Numerical evaluation of wrinkling stress in sandwich panels

Abstract

Sandwich panels have been for years used as structural and cladding elements. Characteristic feature of these structures is that important role is played by temperature actions, creep of the core and local instability of thin faces of the panel [2]. Proper estimation of these phenomena has become a challenging issue because of strong tendency to optimize technical parameters and costs.

The aim of the study is numerical analysis of bending of three-layered panels. In the classical approach linear constitutive equations for faces and core materials are assumed. Moreover, identical tension and compression elasticity modules of the core are introduced [1]. For the plate loaded by axial force P and uniform transversal load q, the following differential equilibrium equation is used:

$$ Bw^{IV} + Pw'' + cw = - q, $$

where w denotes deformation form of compressed face and c is a stiffness coefficient of the core treated as a Winkler foundation. The term B represents the bending stiffness of the plate.

In practice, wrinkling stress depends on many more factors, neglected in analytical solutions, though observed in experiments [3]. In this paper we use numerical methods and hence we can allow for the loss of face adhesion and anisotropy of the core. The analysis is carried out for various dimensions (span and depth of the panel and face thickness) and for various material parameters.

By the way of the parametric analysis, the sensitivity of structural response to variations of dimensional and material parameters will be studied. The range of applicability of classical theoretical models will be discussed basing on numerical examples. The study presented in the paper was inspired by one of the biggest in the world producers of sandwich panels, with the aim to increase safety and economy.