Buckling of laser-welded sandwich panels. Part 1: Elastic buckling parallel to the webs

Abstract

This is the first of three companion papers which examine the elastic buckling and collapse of laser-welded sandwich panels with an adhesively bonded core and uni-directional vertical webs. In compression parallel to the webs the face sheet in between two webs can be treated as a long rectangular plate supported at the sides and resting on a continuous elastic foundation. Using a generalised form of the Kirchoff equation the plate buckling load is evaluated for a Winkler and Pasternak foundation, and for a foundation model where the core is characterised by an elastic halfspace. Although the elastic half-space model is most sophisticated in the way that the decay of transverse stress through the core is described, it requires that the buckling load is calculated iteratively and is therefore not suitable for engineering applications. In contrast, the Pasternak foundation model is able to demonstrate the effect of different boundary conditions at the laser weld and different core properties by the variation of a simple clamping factor and two foundation moduli. By changing the clamping factor the model can be used to describe plate buckling as well as wrinkling, and by varying the foundation moduli it is possible to distinguish between symmetrical and anti-symmetrical buckling modes. Evaluation of the buckling solution shows that for low modulus core materials the plate buckling strength is determined only by the boundary conditions at the laser weld, while for high modulus materials anti-symmetrical wrinkling dominates. To improve the accuracy of the solution for non-standard configurations the foundation moduli are calibrated using the elastic half-space model and finite element results as a reference. It is found that by using a smaller Winkler foundation modulus the accuracy and consistency of the Pasternak model are improved considerably. However, the results also show that for current sandwich configurations the proportional limit of the face plate material is usually reached well before elastic buckling occurs. All experimental work is therefore delegated to the third paper, which deals with extension of the Pasternak foundation model into the elasto-plastic regime and non-linear finite element modeling.

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

“…The elastic buckling models derived in [1,2] are extended into the elasto-plastic regime by using tangent modulus or Engesser theory and the (in)elastic buckling stress is evaluated for both compression cases and global buckling. The 3D finite element model that has been used before is adapted to experimental specifications, and non-linear material and geometrical behaviour are incorporated.…”

Three-Point Bending Behavior of Web-core Steel Sandwich Panel

“…A lot works about sandwich panel buckling strength has been done through analytical methods, finite element methods and experiments [6][7][8]. In these studies, the bending response is evaluated by transforming an originally discrete structure into an equivalent homogenous continuum giving a sandwich panel, or the T-joints of web-core sandwich panel was assumed as continuous features.…”

Influence of general corrosion on buckling strength of laser-welded web-core sandwich plates

“…Kolsters and Zenkert [12], Kolsters and Zenkert [13], and Kolsters [14] studied the local buckling and post-buckling behaviour of face plates. Taczala and Banasiak [15] presented the difference in critical buckling modes and stresses between sandwich and stiffened plates.…”