Bending Of Sandwich Panels Research Articles

In-Plane Bending and Failure Mechanism of Sandwich Beams with GFRP Skins and Soft Polyurethane Foam Core

AbstractThe out-of-plane bending of sandwich panels has been widely investigated, but studies on their behavior under in-plane loading are quite scarce. In this study, 18 sandwich beam specimens were tested under three- and four-point in-plane-bending. The specimens are composed of low-density polyurethane core and glass fiber-reinforced polymer (GFRP) skins on both sides. The shear span-to-depth (a/h) ratio was varied from 1.33 to 4.67. Two different skin thicknesses were also used, providing beam depth-to-skin thickness (h/t) ratios of 47 and 94. It was found that the ultimate moment reduced by approximately one third as the a/h ratio increased from 1.33 to 4.67 in sandwich beams with an h/t ratio of 94 and decreased by about one quarter in beams with an h/t ratio of 47. Doubling the skin thickness [i.e., from h/t of 94–47] increased the moment capacity significantly. The percentage increase ranged from 55 to 95% as a/h increased from 1.33 to 4.67. Failure of sandwich beams occurred by skin wrinkling in...

CHARACTERIZATION OF LOW VELOCITY LOCAL IMPACT OF SANDWICH PANELS

The present paper deals with analysis of local indentation and their energies in point loading of sandwich panel with thin orthotropic composite faces and honeycomb core as an introduction for low velocity impact loading and energy absorbing in sandwich structures. Energy is consumed in two stages: local indentation of sandwich panel skin and bending of sandwich panel. If the impact is located near support or clamping only first stage (indentation of sand-wich panel) will be presented. Here the analytical model has been used assuming a rigid-perfectly plas-tic compressive behaviour of the honeycomb core and membrane behaviour of orthotropic skin for large indentation of sandwich panel. In experimental work were investigated two types of sandwich panels, which consisted of different laminated skins: cross-ply of unidirectional CFRP and AFRP (aramid fabric reinforced plastic) and core honeycomb materials (impregnated paper like Nomex and one layer of glass fabric reinforced plastic). Length of cell side is 2.5 mm. Skins were made with symmetrical lay-ups [0/90]s and [45/-45]s. For indentation test we used steel balls with radius 5-30 mm, speed of loading was 2 mm/min. The experimental results are in good agreement with the analysis. These results can be used in impact loading and energy absorption studies of laminated structures by integrating of “local load vs deflection” curve.

Finite Element Prediction of Mechanical Behaviour under Bending of Honeycomb Sandwich Panels

This paper outlines a finite element procedure for predicting the mechanical behaviour under bending of sandwich panels consisting of aluminium skins and aluminium honeycomb core. To achieve a rapid and accurate stress analysis, the sandwich panels have been modelled using shell elements for the skins and the core. Sandwich panels were modelled by a three-dimensional finite element model implemented in Abaqus/Standard. By this model the influence of the components on the behaviour of the sandwich panel under bending load was evaluated. Numerical characterization of the sandwich structure, is confronted to both experimental and homogenization technique results.

Effects of Gaps between Discontinuous Wire Woven Kagome Cores upon Bending of Sandwich Panels

WBK (Wire-woven Bulk Kagome) is a periodic cellular metal assembled of helical wires. The mechanical behavior under compression or shear, optimal design of a sandwich panel with WBK core, and characteristics of heat dissipation media have been studied, which proves feasibility of WBK as core material with multi-function capability. When WBK is used as the core material in a large scale sandwich panel, gaps between discontinuous cores are inevitable in their fabrication or building even larger scale structures using them. In this study, the effects of the gaps on mechanical behavior of sandwich panels are investigated. Theoretic analysis, experiments with three-point bending, and numerical analyses are performed to predict the strength and to analyze the results

SANDWICH PANELS WITH INTERLAYER SLIP SUBJECTED TO THERMAL LOADS

Thermally induced bending of sandwich panels composed of three symmetrically arranged layers is studied under the consideration of plane strain. Moderately thick elastic layers made of dissimilar transverse isotropic materials are considered. Analyzing two special cases of interlaminar connections, namely, perfect bond and elastic interlayer slip, a complete analogy between the corresponding initial boundary-value problems is derived. Subsequently, the response of the panel with elastic interlayer slip can be determined directly from the solution of the perfectly bonded sandwich panel with moderately thick faces by substituting effective parameters.

A refined model for three-point bending of sandwich panels 2. Transverse stresses

According to the relationships derived in [1], transverse normal and tangential stresses in a sandwich panel have been analyzed. Asymptotic formulas for the stress concentration area in the vicinity of point forces are derived. Analytical estimates of a normal stress at the central and end sections of the panel are deduced. The Saint-Venant effect of the degeneration of a panel of finite length into an infinite strip is studied. For the estimation of the concentration of the transverse tangential stress, the possibility of a superposition of the solution of the slippage problem of the face layers and the classical solution allowing for shear is substantiated. It is shown that the local Reissner-type effects are specified by reducing the concentration of the tangential stress in the face layers along the longitudinal coordinate and transition to the steady tangential stress state in the filler layer. The concentration coefficients of the tangential stress are derived as functions of the dimensional parameters of the panel section.

A refined model for three-point bending of sandwich panels. 1. Deflections and bending stresses

Design formulas for the flexural characteristics of sandwich panels under three-point loading by point forces, taking into account local effects, have been derived. Transverse deformation of the normal in the modified model is deduced in terms of the difference between deflections of face layers. It is considered that the rotation of the normal depends also on shear of the filler. The deflections, local curvatures, and bending stresses, dependent on the face-layer thicknesses and transverse characteristics of the filler, are studied. The danger of initial failure caused by the local moment stresses at the central panel section is shown. Comparative estimates refining the conventional designs are established.

The Buckling and Bending of Orthotopic Sandwich Panels With All Edges Simply-Supported

SummaryA formula is derived for the buckling in compression of an orthotropic sandwich panel, with all edges simply-supported. Two special types of symmetrical sandwiches, that of a sandwich having zero core flexural stiffnesses and of a corrugated core sandwich, are considered, and curves giving the critical buckling end load per inch are presented. An approximate theory is also given for the bending of sandwich panels under the action of an axial compressive load and a uniform lateral pressure. Curves are presented giving the maximum bending moments in a corrugated core sandwich panel.