Showing papers on "Sandwich panel published in 1980"

Method of making sandwich panel

Abstract: Method of manufacturing a sandwich assembly, e.g. an aluminum honeycomb sandwich assembly such as an inboard slat trailing edge for use in an aircraft wherein the spar cap spacing accuracy is retained through break-away tooling, e.g. a strip of low density core machined to the leading edge contour of the honeycomb core during core manufacture.

Composite panel for armouring the interiors of vehicles or the like

Abstract: 1. Bonded panel for armouring vehicle interiors or the like, consisting of an outer rigid armouring panel (10) embedded between two layers (8, 12) of glass fibre reinforced plastics material, an intermediate layer (6) and an inner, softer second armouring panel (2), characterised in that the outer armouring panel (10) is constructed as a continuous panel or is constituted by abutting panel portions and in that the intermediate layer (6) is the core of a sandwich panel bounded on one side by one layer (8) of glass fibre reinforced plastics material embedding the outer armouring panel and on its other side by an additional layer (4) of glass fibre reinforced plastics material.

Shear-Lag Effect in Sandwich Panels With Stiffeners Under Three-Point Bending

Abstract: In this paper, a modified theory based upon Reissner’s procedure for the shear-lag effect of the sandwich panel is presented, which includes the effects of the anisotropy of the faces and the shearing rigidity of the core. In order to verify this theory, bending experiments were performed with sandwich panels composed of a soft core, stiffeners, and orthotropic faces. It was found that the effective bending rigidity calculated from this theory was lower than that derived from the classical bending theory and that the theoretical strain distribution on the faces agreed well with the experimental results.

Noise transmission and attenuation by stiffened panels

Abstract: An analytical study of noise transmission into semi-cylindrical and rectangular acoustic enclosures due to turbulent boundary layer pressure and propeller noise (prop-fan) is presented. The structural noise transmission models include a single panel, discretely stiffened elastic panel and stiffened viscoelastic sandwich panel. Response characteristics of the stiffened panels are evaluated using a transfer matrix procedure. The interior noise field is determined by a Galerkin-like method. The effect on interior noise due to aerodynamic surface flow, cavity back-up pressure, pressurization, mass, stiffness, and damping addition to the structure is investigated. It is shown that stiffened viscoelastic sandwich panels, while providing the same stiffening benefits as an equivalent elastic panel, could significantly reduce vibration levels and subsequently give similar benefits for interior noise control.

Thermally insulating translucent panel is sandwich of two panes - with grating between esp. with voids packed with capillary tubes

Abstract: A thermally insulating, translucent multi-layer or sandwich panel is composed of a grating of elastomer between two panes, the grating is bonded to the panes. Translucent blocks may be incorporated into the voids of the grating, in particular blocks built up of numerous thin-walled capillary tubes. The grating itself is pref. composed of on-edge thin elastomer strips, esp. of silicone rubber. The panes themselves may be of glass or polyvinylfluoride sheet. The multi-layer structure is esp. resistant to deterioration by ultraviolet light.

Response of Graphite/Epoxy Sandwich Panels to Moisture and Temperature Transients

Abstract: The Shuttle Orbiter payload bay door is of graphite/epoxy honeycomb sandwich construction. Interaction of this structure with ground environments prior to first launch leads to an outer facesheet absorbed moisture content of about 1% by weight. During re-entry, the temperature climbs to about 177°C and the accompanying drying cuts this amount to about 0.7%. The high temperature combined with the absorbed moisture causes a substantial decrease in strength. In addition, desorption of water from the nylon/phenolic core causes the internal pressure to reach about 350 kPa. This paper discusses the determination of expected moisture levels, the reduction of graphite/epoxy strength due to moisture and heat, and the internal pressure capability of the sandwich panel. It is shown that the hot moist payload bay door has positive design margins in all areas.

Impact Resistance of Graphite and Hybrid Configurations

Abstract: This paper discusses the effect of several configuration variables on the impact resistance of graphite epoxy laminates. Geometrical effects were evaluated using monolithic panels from 0.04 to 0.18 inch thick or sandwich panels with face sheets from 0.02 to 0.5 inch thick. Separate series of tests were also conducted on 0.5 inch thick monolithic

Problems and Options in Advanced Composite Repair

Abstract: Until recently it has not been clear how large area damage to advanced composite structure could be repaired. Depot level repair concepts recently developed have now demonstrated that such damage is indeed repairable. In fact, restoration of a structural panel to its original strength appears to be entirely possible. After a description of four successful repairs, some of the problems involved and the options available will be discussed.

Self-supporting sandwich panel

Abstract: The panel comprises a layer of insulating material (1) sandwiched between two boards (2, 3) of agglomerated wood chips (chipboard) Laths (4, 5) are provided on one side of the panel This panel is used for building roofs

Tests of graphite/polyimide sandwich panels in uniaxial edgewise compression

Abstract: The local and general buckling behavior of graphite/polyimide sandwich panels simply supported along all four edges and loaded in uniaxial edgewise compression were investigated. Material properties of sandwich panel constituents (adhesive and facings) were determined from flatwise tension and sandwich beam flexure tests. Buckling specimens were 30.5 by 33 cm, had quasi-isotropic, symmetric facings, and a glass/polyimide honeycomb core. Core thicknesses were varied and three panels of each thickness were tested at room temperature to investigate failure modes and corresponding buckling loads. Specimens 0.635 cm thick failed by overall buckling at loads close to the analytically predicted buckling load; all other panels failed by face wrinkling. Results of the wrinkling tests indicated that several buckling formulas were unconservative and therefore not suitable for design purposes; a recommended wrinkling equation is presented.

Interlaminar Stress Gradients and Impact Damage

Abstract: The sensitivity of laminates to low velocity impact damage is a practical design problem that the ASTM and others have been investigating for several years. One of the difficulties in studying impact response is predicting the complex interlaminar stress gradients that it produces in composite structures. The present paper presents a systematic approach to interlaminar stress gradient modeling with applications to graphite-epoxy laminates impacted by a steel sphere. The approach is based on a family of variable property finite elements for laminate models that transition to discrete ply models for regions with interlaminar stress gradients. All 45 elastic constants for a general anisotropic laminate are simulated and considerable error is shown to occur when uniform properties are used with certain laminate models. Careful modeling of the force-deformation behavior is required to predict accurate boundary conditions in the impact region when bending is present. Numerical results are presented for a sandwich panel and a thick 48 ply laminate. High local bending stresses in the skin dominate the sandwich panel and significant subsurface shear occurs in the thick laminate.