Experimental study of laser welded joint failure and overall ultimate strength for I-core sandwich panels

Abstract

To meet the demand for lightweight ship structures, I-core sandwich panels are used in the main load-bearing structure of ships, where the panels and the core web are connected to form a whole by means of laser penetration welding, and the connecting area often becomes the weak link of the structure. In conventional ship construction, welds are generally assumed to be sufficiently strong. However, the laser penetration process in I-core sandwich panels reveals inconsistencies with this assumption, and there is a lack of research related to localized failures of welded joints. In this paper, I-core sandwich panels are taken as the research object to carry out the ultimate strength experiment of I-core sandwich panels, measure the stress and deformation behaviors of the experiment model under in-plane compression load, capture the failure mode of cracking at the weld of I-core sandwich panels, and obtain the load-displacement curve of I-core sandwich panels containing the failure at the weld. Subsequently, this paper adopts a nonlinear finite element method to study the failure behavior of I-core sandwich panels under in-plane compressive loads, comparing the numerical calculation results with the experimental results and analyzing the effects of initial deformation patterns and amplitudes on the ultimate strength. On this basis, this paper establishes the refined analysis model of failure of laser welded T-joints, forms the bending moment angle curve of laser-welded T-joint structure, establishes the simplified method of the overall ultimate strength analysis of sandwich panel model by failure of laser welded T-joints, and puts forward the prediction formula of the ultimate load bearing capacity of I-core sandwich panel. The results indicate that I-core sandwich panels are vulnerable to welded joint failure, which leads to overall structural collapse through localized plate buckling; when the failure of the laser welded area is ignored, there is a large deviation between the results of the nonlinear finite element calculations and the experiment results, so that the ultimate strength assessment of I-core sandwich panels can not ignore the influence of failure at the weld; in order to avoid premature failure at the welded area of I-core sandwich panels, the width of the T-type laser welds is recommended to be not less than 0.36 times the core plate thickness. The findings of this paper can provide experimental results and evaluation methods for the limit design of I-core sandwich panels.