Buckling and free vibration of laser-welded web-core sandwich panels: Extreme sensitivity to variation of weld rotational stiffness

Abstract

T-joints in laser-welded web-core sandwich panels connect face-plates with web-plates. Rotational stiffness of the T-joints affects transverse shear stiffness of the panels. In this paper we describe the effect of geometric and material parameters on the rotational stiffness of the T-joints, and show that laser weld thickness bears the highest influence. The analysis is performed using detailed FEM models of the joints that include laser welds. The effect is translated to critical buckling and first natural frequency of laser-welded web-core sandwich panels. Structural analyses are performed using equivalent single layer model with the first order shear deformation theory. The models used in this research are validated using experiments and numerical results from literature. The most sensitive and the least sensitive panels to variation of the rotational stiffness are outlined by means of global optimization. We describe them in terms of stiffness coefficients and design variables. The analysis reveals that insensitive panels have small height and small distance between web-plates, and as such have low structural performance for their area density. Panels with the best structural performance are generally quite sensitive to variation of the rotational stiffness, but the sensitivity can be even higher in other panels. It was found that rotational stiffness of T-joints is important in design and optimization of the panels, since the best performing panels of the same area density have different cross-sections for different rotational stiffness.