Buckling of laser-welded sandwich panels. Part 2: Elastic buckling normal to the webs

Abstract

This is the second of three companion papers that examine the elastic buckling and collapse of laser-welded sandwich panels with an adhesively bonded core and uni-directional vertical webs. In the first paper, it has been shown that the critical load in compression parallel to the webs can be accurately predicted by using a Pasternak foundation to model the core and by using a simple clamping factor to describe the boundary conditions at the laser weld. In this paper, the same model is adapted to predict the critical load in compression normal to the webs. As the face plate is now short and wide, rather than long and narrow as before, a ‘constrained wrinkling’ approach is outlined that recognises that the face plate is limited in its ability to wrinkle naturally and can only deform in certain mode shapes. The clamping factor and the effective wave length are derived for different buckling mode shapes and boundary conditions at the laser weld, and the constrained wrinkling load is determined by evaluating the buckling load for successive modes and simply picking the smallest value. It is shown that, for low modulus core materials, the constrained wrinkling load is equal to the bare plate buckling load and, for high modulus materials, the solution converges toward anti-symmetrical wrinkling, as has been found for the case of compression parallel to webs. The constrained wrinkling load agrees well with finite element results but as before the proportional limit of the face plate material is usually reached well before elastic buckling occurs.