Parametric study of the post-buckling strength of structural core sandwich panels (original) (raw)
Post-buckling strength of simply supported orthotropic corrugated board panels subjected to edge compressive loading has been investigated using geometrically non-linear finite element analysis (FEA). Adjustments of the transverse shear stiffnesses in the FEA were necessary and performed by comparing the critical buckling load calculated by FEA with a closed form solution. The collapse load of the sandwich plate was calculated based on material failure of the facings predicted from Tsai-Wu failure theory. Parametric studies were performed to investigate the sensitivity of the collapse load to changes in the transverse shear stiffnesses of the core, initial out-of-plane imperfections, asymmetry in board construction, slenderness ratio and eccentric loading of the plate. It was found that a reduction of the transverse shear stiffnesses of the core below a certain limit produces a significant reduction in the collapse load. Panels are said to be insensitive to imperfections and this holds true when the imperfections are the same as or lesser than the thickness of the panel, but a 40% reduction of the collapse load is observed for imperfections that are ten times the panel thickness. From a design point of view it is shown that a symmetrical board is preferred because an asymmetric board as well as eccentric loading of the panel significantly reduce the collapse load. It is also shown that the critical buckling load is directly related to the slenderness ratio of the panel whereas the collapse load is not.
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Davies and Hakmi (1990) [5] studied the local buckling behaviour of a compressed plate element supported by relatively weak isotropic core medium. When the sandwich panel is subjected to uniform compression the authors represented the panel as a simply supported plate resting on half space linear elastic foundation. The critical buckling stress was determined using the principle of minimum strain energy method following Timoshenko and Gere‟s method (1961). For simply supported plates without foundation they added the strain energy contribution for the core assuming it to be the elastic foundation with exponentially decaying displacement. Parameter representing the decay in the displacement of the core was found by minimizing the strain energy. This leads to a formula for the buckling coefficient of sandwich pane which is used to achieve the ultimate strength of plate using the effective width concept (i.e.Winter formula). The authors found that the results did not quite agree with the experimental results. Improved correlation was obtained by arbitrarily reducing the value of an intermediate parameter. Davies and Hakmi (1991) [6] reviewed the analytical methods for the evaluation of buckling stress of sandwich panels for plane and profiled faces. They developed analytical formula for wrinkling stress based on considering the core as an elastic half space, by treating the width of the plate as wider flat face (i.e. width of the plate increases to infinity), this formula is modified for lightly profiled faces by introducing the effect of flexural rigidity of profiled face. Also the authors introduced practical design reduction factors for both cases due to imperfection and material non-linearity. For the profiled sandwich panels authors adopted design formula similar to Winter formula based on experimental mean values and numerical post-buckling analysis.The sandwich panels, one of the attractive engineering structures mixed between two different materials to achieve high ultimate strength associated with light weight structures. Usually, the sandwich panels comprise of foam core and thinner high strength steel faces. This report discusses currently design formulae of local buckling behaviour of sandwich panels with profiled faces using finite element method. Multiple wave finite element models adopted to investigate and examine the adequacy of currently approach for design. This report presents the details of examining the FEA model including geometry, dimensions, load pattern and boundary conditions. The FEA model gives well agreement using experimental programme of Pokharel and Mahendran (2003). However, it appears the currently design formulae are conservative for the plate elements with low b/t ratios while over conservative for high b/t ratios (slenderness plate). A unified design formula of local buckling behaviour is developed.
1Buckling Analysis of Corrugated Core Sandwich
2014
In an effort to improve structural design of corrugated board packages under compression load, buckling analysis of simply-supported corrugated board panels, which constitute the main load-bearing components of a compression loaded box, has been performed. This paper focuses on prediction of effective (homogenised) properties of the corrugated core and the critical buckling load of a simply-supported board panel. An improved buckling load prediction has been obtained by incorporation of the additional moments produced by transverse shear deformation in the governing differential equation for equilibrium. The buckling load predictions are compared to previous analytical formulations, finite element analysis and experiments.
On global and local buckling response of structural angle sandwich panels
Thin-Walled Structures, 2022
Having in mind the topic of industrialised construction and the benefits of modular construction, sandwich panels are investigated to be utilised as load-bearing wall elements. To assess its full potential, the present paper tackles the linear elastic buckling response of axially loaded angle sandwich panels, by means of numerical and analytical calculations, as the upper bound of its load bearing capacity. The failures modes are obtained and framed for concentrically loaded angle panels with fixed and pin-ended supports. A parametric study of the angle panel comprising a series of finite element models is undertaken where responses are compared with analytical calculations based on the theory of sandwich panels. Boundaries for local and global buckling are identified and framed.
Past research in Europe and the USA (Davies, Hakmi 1987, 1990, 1992, 1993, Hassinen 1995, ECCS,2000) has investigated the local buckling behaviour and developed modified conventional effective width rules for the plate elements in sandwich panels. However, these studies have been based on polyurethane foams and lower grade steels, and rely on some empirical factors. Moreover, these rules can be applied only for low width to thickness (bit) ratios (Figure 2) of the plate elements. But in the sandwich panel construction, bit ratios can be as large as 600 (Mahendran and Jeevaharan, 1999). Therefore a research project was conducted using a series of experiments and numerical analyses to study the local buckling behaviour of sandwich panels made of high strength steel faces and polystyrene foam covering a wide range of bit ratios. The Australian sandwich panels use polystyrene foam and thinner (0.42 mm) and high strength steels (G550 with a minimum yield stress of 550 MPa), which are bonded together using separate adhesives. Therefore a research project on Australian sandwich panels was undertaken using experimental and finite element analyses. The experimental study on 50 foam-supported plate elements and associated finite element analyses produced a large database for sandwich panels subject to local buckling effects, but revealed the inadequacy of conventional effective width formulae for panels with slender plates. It confirmed that these design rules could not be extended to the slender plates in their present form. In this research, experimental and analytical results were used to improve the design rules. This paper presents the details of experimental and finite element analyses, their results and the improved design rules.
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