Buckling of laser-welded sandwich panels: Ultimate strength and experiments

This is the last of three companion papers which examine the elastic buckling and collapse of laser-welded sandwich panels with an adhesively bonded core and unidirectional vertical webs. By evaluation of the buckling stress in the first two papers it has been found that the buckling stress in compression parallel and normal to the webs typically reaches the proportional limit of the face plate and web material well before elastic buckling occurs. Hence, this paper presents an extension of the buckling model into the elastoplastic regime, with the aim of determining the ultimate (local) strength of the sandwich and of allowing experimental verification of the results. Using tangent modulus theory to ‘plasticize’ the elastic buckling model, the ultimate strength is evaluated for a sandwich configuration with high-strength steel face plates and a broad range of core moduli. The critical load predicted by the inelastic buckling model agrees well with non-linear finite element results and experimental values obtained from compression testing.