Showing papers on "Sandwich-structured composite published in 1979"

Multiwall thermal protection system

Abstract: Multiwall insulating sandwich panels are provided for thermal protection of hypervelocity vehicles and other enclosures. In one embodiment of the invention the multiwall panels are formed of alternate layers of dimpled and flat metal (titanium alloy) foil sheets and beaded scarfed edge seals to provide enclosure thermal protection up to 1000° F. An additional embodiment employs an intermediate fibrous insulation for the sandwich panel to provide thermal protection up to 2000° F. and a third embodiment employs a silicide coated columbium waffle as the outer panel skin and fibrous layered intermediate protection for thermal environment protection up to 2500° F. The use of multiple panels of the present invention on an enclosure facilitate repair and refurbishment of the thermal protection system due to the simple support provided by the tab and clip attachment for the panels.

Tie anchor for sandwich panels of reinforced concrete

Abstract: Tie anchor for sandwich panels of reinforced concrete in the form of a metal strip of undulated zigzag shape whose loop portions are anchored in the concrete panel layers and whose connecting leg portions reach through the intermediate insulating layer. Two central leg portions of the tie anchor are oppositely inclined to form a rigid central connecting point between the panel layers, while all other leg portions are parallel, to allow for limited panel displacements, under unequal thermal expansion.

Method of manufacture of honeycomb noise attenuation structure and the resulting structure produced thereby

Abstract: Method of manufacturing broad band noise attenuation sandwich panels utilizing a cellular core positioned between and bonded to two facing sheets by an adhesive bonding system. One facing sheet is perforated and the other imperforate. A thin sheet of porous fibrous felt or fabric is bonded to the outer surface of the perforate sheet. The adhesive layer, at least between the perforate sheet and the porous fibrous material, is sufficiently thick to isolate the two components and form a funnel shaped opening necked down at the entrance to each perforation. In one embodiment a thin layer of non-metallic cloth is positioned between the perforated and porous fibrous material in those areas where cutting, trimming or drilling of the completed structure is required to maintain isolation.

Method of manufacturing of honeycomb noise attenuation structure and the structure resulting from the method

Abstract: Method of making attenuation sandwich panels having a cellular core positioned between and bonded to an imperforate facing sheet on one surface thereof and a perforate sheet with an outer layer of porous fabric material adhered to the other surface. The combined perforate facing sheet and porous fibrous material have a predetermined open surface area prior to its adherence to the cellular core. A coating of adhesive is applied to either the facing sheets or to the facing surface of the cellular core. The sheets are then properly positioned with respect to the cellular core. The porous fabric surface of the combined perforate sheet and porous fibrous material is positioned against a perforated plate. The opposite surface of the perforated plate is positioned against a bonding tool that has a plurality of longitudinal grooves on its perforated plate adjacent surface. This combination is then placed in a press or the like where pressure is applied from the facing sheets towards the core and is then heated until the adhesive is cured.

Composite panels which are not easily combustible

Abstract: An improved lightweight, flame resistant composite panel is disclosed which is readily shaped at room temperature without the necessity of machining. The composite panel comprises a foamed rigid thermoplastic core sandwiched between a pair of metallic layers. The thermoplastic core contains inorganic fillers in powder form to add further flame resistant characteristics to the composite panel. The metallic layers are bonded to the core by means of a thin layer of adhesive which exhibits good strength at elevated temperatures.

Thick Skin Sandwich Beam Columns with Weak Cores

Abstract: An analytical method for predicting the behavior of sandwich beam columns was developed for cases where thick skins and weak cores are utilized. It is anticipated that this analytical tool will help in the design of this type of elements for buildings where the other functions (i.e., thermal and acoustic insulation) can also be satisfied in an integrated design. Analytical expressions were derived for seven loading conditions, the most complicated of which was with end thrusts and end moments and a concentrated midspan load, all acting on an initially bowed beam-column. As an example, additional design equations were derived for this loading condition so that stresses and strains in the skins and core could be evaluated. This analytical tool has proven to be useful in the design of prototype sandwich panels.

Structural Sandwich Performance After 31 Years of Service.

Abstract: : Study of the design and fabrication of structural sandwich panels was initiated at the Forest Products Laboratory in the mid 1940's. It was recognized that, even with extensive basic research, additional information would be needed on the long-term serviceability and durability of sandwich panels as a building component. Accordingly, an experimental unit was built on the laboratory grounds in 1947 to provide for long-term exposure tests of panels. Selected sandwich panels placed in the exposure unit were evaluated for bending strength and stiffness after various lengths of service between the years 1947-1978. Panels were constructed with a variety of facing materials including plywood, aluminum, particleboard, hardboard, paperboard, and cement asbestos, and with cores of paper honeycomb, polyurethane, and extruded polystyrene. Measurements were kept of the bowing of panels due to seasonal climatic changes. This information should be useful to building manufacturers, building code authorities, and others concerned with design and manufacture of housing. (Author)

Finite Strip Laminated Sandwich Roof Analysis

Abstract: The finite strip method is extended and applied to the analysis of sandwich folded plate and cylindrical shell roofs supported on diaphragms. In addition to accounting for the transverse shear deformations in an orthotropic core, local bending and bending-membrane coupling effects in cross-ply laminated faces are considered. The formulation is presented in terms of the membrane, bending and coupling stiffnesses of the faces, and the transverse shear rigidities of the core. Displacements are approximated by assumed functions that satisfy the boundary conditions at the diaphragms and which provide the capability of imposing appropriate continuity conditions between adjacent strips. Sample results are presented for roofs with cross-ply laminated faces indicating the effects of bending-membrane coupling.

Lateral deflection of a sandwich-panel building model under combined loading

Abstract: The behavior of a half-scale panelized building model subjected to, lateral and vertical loads has been analyzed both experimentally and theoretically. The model wa made up of 2-in.-thick sandwich panels with styrofoam core and .025-in.-thick aluminum facings stapled together with aluminum extrusions. Comparisons of the results with the design wind and seismic loads of the Uniform Building Code shows the reliable structural performance of this type of structural system.

Nonlinear Elastic Analysis of Panelized Shear Sandwich Walls

Abstract: Light-weight sandwich panel assemblies can be prefabricated, mass-produced, easily transported, and effectively erected with a small crew and no crane. A one-half scale, six-story building model made up of 2-in. (51-mm) thick aluminum sandwich panels and stapled connections resisted lateral loads of up to 83.3 psf (4,000 kN/m²) representing reference wind speeds of over 93 mph (150 km/hr). An analytical approach has been developed to predict deflections and stresses of panelized building structures having friction-variable shear connections that give rise to nonlinear behavior of the structure. Theoretical and experimental results compared within an average of 6% and a maximum of 13%.

Manufacturing processes for fabricating graphite/PMR 15 polyimide structural elements

Abstract: Investigations were conducted to obtain commercially available graphite/PMR-15 polyimide prepreg, develop an autoclave manufacturing process, and demonstrate the process by manufacturing structural elements. Controls were established on polymer, prepreg, composite fabrication, and quality assurance, Successful material quality control and processes were demonstrated by fabricating major structural elements including flat laminates, hat sections, I beam sections, honeycomb sandwich structures, and molded graphite reinforced fittings. Successful fabrication of structural elements and simulated section of the space shuttle aft body flap shows that the graphite/PMR-15 polyimide system and the developed processes are ready for further evaluation in flight test hardware.

Comprehensive strength analysis of framed sandwich panels

Abstract: Local instability of thin facings in sandwich panels often leads to wrinkling at stresses lower than yield stresses. An investigation was carried out by the authors on the behaviour of the facings of rectangular sandwich panels having thin aluminum faces and styrofoam core when subjected to edgewise compression and (or) out-of-plane bending. A set of the panels had no additional reinforcement at the edges whereas others were either totally or partially reinforced with wood framing integrated along the edges. Existing formulae developed to predict these stresses were found to overestimate results obtained from a test programme conducted by the authors. New expressions are presented for wrinkling and ultimate loads for sandwich panels with various edge conditions. A comparison is made between existing and newly derived expressions.

The structural behavior of a graphite-polymide honeycomb sandwich panel with quasi-isotropic face sheets and an orthotropic core

Abstract: The results of a series of tests of graphite-polyimide honeycomb sandwich panels are presented. The panels were 1.22 m long, 0.508 m wide, and approximately 13.3 m thick. The face sheets were a T-300/PMR-15 fabric in a quasi-isotropic layup and were 0.279 mm thick. The core was Hexcel HRH 327-3/16 - 4.0 glass reinforced polyimide honeycomb, 12.7 mm thick. Three panels were used in the test: one was cut into smaller pieces for testing as beam, compression, and shear specimens; a second panel was used for plate bending tests; the third panel was used for in-plane stability tests. Presented are the experimental results of four point bending tests, short block compression tests, core transverse shear modulus, three point bending tests, vibration tests, plate bending tests, and panel stability tests. The results of the first three tests are used to predict the results of some of the other tests. The predictions and experimental results are compared, and the agreement is quite good.