Showing papers on "Sandwich panel published in 1997"

Honeycomb Technology: Materials, Design, Manufacturing, Applications and Testing

Abstract: Introduction. Honeycomb core. Sandwich design. Honeycomb processes. Sandwich fabrication. Structural applications. Other honeycomb applications. Honeycomb and sandwich testing. Sandwich panel repair. Appendix. Index.

Modular polymer matrix composite support structure and methods of constructing same

Abstract: A load bearing deck (20) of a modular structural section (30) for use in a support structure such as a load bearing deck or highway bridge. The at least one modular structural section (30) includes at least one beam (50) and a load bearing deck (20) preferably formed of a polymer having elongate core members (46) having a polygonal shape, preferably a trapezoidal shape. Alternatively, the load bearing deck comprising at least one sandwich panel (30) is suitable for applications such as barge decks, hatchcovers, and other load bearing wall applications. Methods of constructing a support structure utilizing the modular structural section (30) including the polygonal, preferably trapezoidal core deck, and support members (22) are also provided.

Stitch-reinforced sandwich panel and method of making same

Abstract: A stitch-reinforced sandwich panel with improved flatwise tensile strength, improved skin to core peel strength, and substantially reduced damage propagation from impact includes a relatively non-compressible foam core, a dry reinforcing layer of fibers placed on each of the opposite faces of the foam core; and high strength thread stitched with a high density of stitches over the entire panel through each of the reinforcing layers and the foam core. The skins are then impregnated with a resin system to complete the structure.

Stability of Functionally Graded Shape Memory Alloy Sandwich Panels

Abstract: The stability of sandwich panels subjected to the simultaneous action of a uniform temperature and a uniaxial compression is considered. At elevated temperatures, the buckling load can be increased by using shape memory alloy (SMA) fibers in resin sleeves embedded within the core, at the midplane of the sandwich panel. The best results are achieved when the spacing of SMA fibers across the panel is nonuniform, i.e. the spacing, which is minimum at the centerline, gradually increases with the approach to the edges (sinusoidal distribution). The effectiveness of SMA fibers increases with temperature due to larger tensile recovery stresses. The example of stability of sandwich panels considered in the paper illustrates that functionally graded SMA composites may present significant advantages in engineering design.

Concrete sandwich panel erection anchor

Abstract: An anchor adapted for being embedded within a concrete sandwich panel to facilitate lifting thereof is disclosed. The anchor includes a neck supporting a head adapted for mating with a conventional lifting assembly. The neck is supported on a body portion adapted for being at least partially embedded within the sandwich panel. The body portion includes a pair of opposing wings extending radially outwardly from a central axis wherein each wing includes an inner portion adapted to be embedded within a wythe of insulation and an outer portion adapted to be embedded within a wythe of concrete.

Method for forming inner mold line tooling without a part model

Abstract: A method of forming a caul plate (14) for use in producing a composite honeycomb core sandwich panel (27). The uncured honeycomb core sandwich panel (27) is laid-up on a lay-up mandrel (20). An inner bagging film (28) is then extended over the uncured honeycomb core sandwich panel (27). Tooling prepreg sheets (34) are extended over the inner bagging film (28), and a outer bagging film (40) is extended over the tooling prepreg sheets (34). Reduced vacuum is applied to the inner bagging film (28), and full vacuum is applied to the outer bagging film (40). The tooling prepreg sheets (34) are then partially cured so that they harden into the shape of the inner mold line of the honeycomb core sandwich panel (27). The partially cured tooling prepreg sheets (34) are then final cured to form the caul plate (14). The caul plate (14) can then be used for inner mold line tooling for the honeycomb core sandwich panel (27) or parts having the same inner mold line shape.

Advanced Technology Composite Fuselage: Program Overview

Abstract: The Advanced Technology Composite Aircraft Structures (ATCAS) program has studied transport fuselage structure with a large potential reduction in the total direct operating costs for wide-body commercial transports. The baseline fuselage section was divided into four 'quadrants', crown, keel, and sides, gaining the manufacturing cost advantage possible with larger panels. Key processes found to have savings potential include (1) skins laminated by automatic fiber placement, (2) braided frames using resin transfer molding, and (3) panel bond technology that minimized mechanical fastening. The cost and weight of the baseline fuselage barrel was updated to complete Phase B of the program. An assessment of the former, which included labor, material, and tooling costs, was performed with the help of design cost models. Crown, keel, and side quadrant cost distributions illustrate the importance of panel design configuration, area, and other structural details. Composite sandwich panel designs were found to have the greatest cost savings potential for most quadrants. Key technical findings are summarized as an introduction to the other contractor reports documenting Phase A and B work completed in functional areas. The current program status in resolving critical technical issues is also highlighted.

On the design and analysis of continuous sandwich panels

Abstract: Interaction between the bending moment and support reaction introduces new failure modes at intermediate supports of continuous sandwich panels. Two different loading cases have to be separated in the design. Positive support reaction causes a compressive contact pressure between the supporting structure and sandwich panel, and negative support reaction tensile forces in the fasteners of the panels. In the paper, the loading case named the positive support reaction is studied by means of analytical models, numerical analyses and experimental results. The analyses result in recommendations for the design at the serviceability state.

Panel material and method of manufacturing the same

Abstract: The panel material of the present invention comprises (A) two sheets of FRP molded board as upper and lower surface materials, and, as a core material, (B) a high density, rigid polyurethane foam layer which has been obtained by injecting a rigid polyurethane foam starting material between these two sheets of FRP molded board and allowing this starting material to foam, and which has a closed cell structure and a density of 0.2˜0.5 g/cm3. In addition, the manufacturing method of the panel material of the present invention includes a process for obtaining an integrally molded sandwich panel by injecting a rigid polyurethane foam starting material into a space between two sheets of FRP molded board which have been set in a mold, and allowing it to foam; and a process in which panel material is made by cutting this sandwich panel to a desired size. The panel material of the present invention is particularly suitable for use as flooring in vehicles such as trucks, buses, railway rolling stock, freight containers, and the like.

Evaluation of a Composite Sandwich Fuselage Side Panel With Damage and Subjected to Internal Pressure

Abstract: The results from an experimental and analytical study of a composite sandwich fuselage side panel for a transport aircraft are presented. The panel has two window cutouts and three frames, and has been evaluated with internal pressure loads that generate biaxial tension loading conditions. Design limit load and design ultimate load tests have been performed on the graphite-epoxy sandwich panel with the middleframe removed to demonstrate the suitability of this two-frame design for supporting the prescribed biaxial loading conditions with twice the initial frame spacing of 20 inches. The two-frame panel was damaged by cutting a notch that originates at the edge of a cutout and extends in the panel hoop direction through the window-belt area. This panel with a notch was tested in a combined-load condition to demonstrate the structural damage tolerance at the design limit load condition. The two panel configurations successfully satisfied all design load requirements in the experimental part of the study, and the three-frame and two-frame panel responses are fully explained by the analysis results. The results of this study suggest that there is potential for using sandwich structural concepts with greater than the usual 20-in.-wide frame spacing to further reduce aircraft fuselage structural weight.

Moisture ingression in honeycomb core sandwich panels

Abstract: Moisture ingression was studied in several composite sandwich panels, in which hydration was applied over a large surface area at the panel edges. Significant moisture ingression occurred in panels with cores of Korex (based on a substrate of a fiber pulp paper) and HRP (consisting of a woven-glass-fiber substrate with a polymer coating) of different density. Ingression was more rapid than in panels with hydration applied locally. Ingression followed an exponential pattern in time in most cases, in harmony with diffusion theory.

Impact test device

Abstract: PROBLEM TO BE SOLVED: To load impact under the almost real condition and to adjust impact level by fixing a device to the central part of a rectangular panel manufactured with the use of a general honeycomb sandwich panel and providing a device, which is driven with air pressure so as to produce the impact, on four corners of the panel. SOLUTION: A device 1 is fixed to the center of a rectangular honeycomb sandwich panel 9 with a bolt. The four corners of panel 9 are hung with ropes 7. And air pressure drive impact production devices 10 are fixed to the four corners of the panel 9, respectively. With a hose 11 in between, the impact production device 10 and a compressor 12 are connected to each other. The compressed air produced with the compressor 12 is supplied to the device 10 through the hose 11, for driving the device 10. The impact produced at the device 10 is propagated to the device 1 through the panel 9.

Thermostructural Behavior of a Hypersonic Aircraft Sandwich Panel Subjected to Heating on One Side

Abstract: Thermostructural analysis was performed on a heated titanium honeycomb-core sandwich panel. The sandwich panel was supported at its four edges with spar-like substructures that acted as heat sinks, which are generally not considered in the classical analysis. One side of the panel was heated to high temperature to simulate aerodynamic heating during hypersonic flight. Two types of surface heating were considered: (1) flat-temperature profile, which ignores the effect of edge heat sinks, and (2) dome-shaped-temperature profile, which approximates the actual surface temperature distribution associated with the existence of edge heat sinks. The finite-element method was used to calculate the deformation field and thermal stress distributions in the face sheets and core of the sandwich panel. The detailed thermal stress distributions in the sandwich panel are presented, and critical stress regions are identified. The study shows how the magnitudes of those critical stresses and their locations change with different heating and edge conditions. This technical report presents comprehensive, three-dimensional graphical displays of thermal stress distributions in every part of a titanium honeycomb-core sandwich panel subjected to hypersonic heating on one side. The plots offer quick visualization of the structural response of the panel and are very useful for hot structures designers to identify the critical stress regions.

Light weight and waterproof honeycomb sandwich panel manufactured by resin transfer molding

Abstract: PROBLEM TO BE SOLVED: To manufacture a lightweight and waterproof composite panel of an open cell material like a honeycomb by using a resin transfer molding(RTM) SOLUTION: An open cell core material 1 is bonded to a resin/moisture shielding film 3 consisting of a specific polymer film with a film adhesive 2 before injecting a liquid resin into a fibrous reinforcing material 4 in an RTM step Consequently, the sealing is achieved to the degree of at least, 95%, and further, even to 100% Thus, the open cell core material 1 is prevented from being filled with a resin in the RTM step and is isolated from the migration of moisture after the use of this honeycomb sandwich panel Thus the composite panel manufactured by the RTM method is suited for an aircraft

Heat pipe sandwich panel

Abstract: PROBLEM TO BE SOLVED: To obtain a heat pipe sandwich panel constituting the structure of a satellite in which a heating apparatus is prevented effectively from temperature rise by employing carbon fiber reinforced carbon at a part of a skin material touching a heat pipe. SOLUTION: A heat pipe sandwich panel comprises a skin material 6 of carbon fiber reinforced plastic composed of continuous carbon fiber and matrix of organic material for in-plane reinforcement, an aluminum honeycomb core 2, an adhesive 3 and an embedded heat pipe 1 wherein a heating apparatus 4 is fixed to the outside of the skin material 6. A part of the skin material 6, preferably the part for mounting the heating apparatus 4, is made of a skin material 7 employing carbon fiber reinforced carbon. Since the skin material 7 exhibits excellent thermal conductivity even in the out-plane direction, heat resistance can be decreased between the heating apparatus 4 and the heat pipe and the heating apparatus is prevented from temperature rise. COPYRIGHT: (C)1999,JPO

NDE of composite materials by thermal method and shearography

Abstract: This paper reports a comparison among different thermal techniques and shearography applied to a sandwich panel of composite material containing simulated defects. In particular, the detectability of the defects and the evaluation of the planar extension are examined. An important feature is also the classification of different kinds of defects. The experimental and data processing procedures are described for all methods. For the thermal method, a mathematical simulation of the thermal problem allows us to better design the test. Automatic processing of data are presented giving outputs very simple to understand.

Structural panel collector for solar heating of liquids

Abstract: A sandwich panel (1) has metal walls and a core of insulating foam. One side has a profiled surface in the form of ridges (2) extending in the lengthwise direction of the panel. Pipes (4) convey the heat exchanger medium or water into the reflector type recesses (3) between the ridges. The pipes are fixed to the wall of the panel thus providing direct metal contact with the panel walls and pipes. A connector (5) for the pipes goes through holes (6) from the absorber side to the rear side of the sandwich panel. The recesses contain extra heat accumulator elements (7) in the for of expanded metal.

Honeycomb and sandwich testing

Abstract: There are many tests that can be used to obtain the mechanical properties and structural integrity of honeycomb cores and sandwich panels. This chapter discusses the various tests and explains some of the statistical methods used to analyze the results.

Shelter formed into panel structure

Abstract: PROBLEM TO BE SOLVED: To first protect a sealant so as to maintain waterproofing effect, and to second prevent the occurrence of water leaking accident through the such improvement of the waterproofing effect, and to third simply and easily realize the above prevention. SOLUTION: In this shelter, a honeycomb sandwich panel 3 functioning as a face plate is severally attached between corner frames 1 functioning as a framework arranged lengthwise and breadthwise, and the shelter is therefore wholly box-shaped and equipped with a door, and accommodates apparatus, equipment and materials, baggage and other articles in an inner part D, and is moved and installed. The end part 4 of the honeycomb sandwich panel 3 is severally fitted and joined in the fitting part 2 of each corner frame 1 to at least compose a roof A sealant 6 used between the corner frame 1 and the honeycomb sandwich panel 3 is severally applied from the outside to the neighborhood of fitted and joined portions between them, and the roof A is covered with a cover plate 14.

Panel construction-method building

Abstract: PROBLEM TO BE SOLVED: To obtain a building frame system using no column and beam, being easily executed and having the high degree of freedom by constituting a roof, an external wall, a floor, etc., by employing sandwich panels, in which metal plates are installed on both surfaces of core materials consisting of a foamed resin, as a bearing wall. SOLUTION: Metal plates 3 longer than the vertical direction by specified length are mounted on both surfaces of a core material 2 composed of a heat-insulating material, notched sections 1b, in which the core material 2 is notched by specified width along the longitudinal direction, are formed at the left and right ends of a sandwich panel 1, in which fitting sections are formed at upper and lower ends, and the end faces of the metal plates 3 are folded back to the insides and folded-back sections 3a are formed beforehand. The folded-back sections 3a are connected through joint members 4 in connection in the horizontal direction or the lateral direction of each of roof panels 8, external-wall panels 9 and floor panels 10. Joint members such as artificial wood are fitted to the fitting sections of the sandwich panels 1, and clamped and connected by tapping screws, etc., in connection in the height direction or the vertical direction. Accordingly, the structure of a building is simplified, and the term of works can be shortened largely.