Showing papers on "Sandwich panel published in 2004"

Dynamic Response of a Clamped Circular Sandwich Plate Subject to Shock Loading

Abstract: An analytical model is developed for the deformation response of clamped circular sandwich plates subjected to shock loading in air and in water. The deformation history is divided into three sequential stages and analytical expressions are derived for the deflection, degree of core compression, and for the overall structural response time. An explicit finite element method is employed to assess the accuracy of the analytical formulas for the simplified case where the effects of fluid-structure interaction are neglected. The sandwich panel response has only a low sensitivity to the magnitude of the core compressive strength and to the degree of strain hardening in the face-sheets. The finite element results confirm the accuracy of the analytical predictions for the rigid ideally plastic sandwich plates. The analytical formulas are employed to determine optimal geometries of the sandwich plates that maximize the shock resistance of the plates for a given mass. The optimization reveals that sandwich plates have a superior shock resistance relative to monolithic plates of the same mass. @DOI: 10.1115/1.1778416#

Analysis, Design and Optimization of Non-Cylindrical Fuselage for Blended-Wing-Body (BWB) Vehicle

Abstract: Initial results of an investigation towards finding an efficient non-cylindrical fuselage configuration for a conceptual blended-wing-body flight vehicle were presented. A simplified 2-D beam column analysis and optimization was performed first. Then a set of detailed finite element models of deep sandwich panel and ribbed shell construction concepts were analyzed and optimized. Generally these concepts with flat surfaces were found to be structurally inefficient to withstand internal pressure and resultant compressive loads simultaneously. Alternatively, a set of multi-bubble fuselage configuration concepts were developed for balancing internal cabin pressure load efficiently, through membrane stress in inner-stiffened shell and inter-cabin walls. An outer-ribbed shell was designed to prevent buckling due to external resultant compressive loads. Initial results from finite element analysis appear to be promising. These concepts should be developed further to exploit their inherent structurally efficiency.

Local effects in the vicinity of inserts in sandwich panels

Abstract: The paper considers local bending effects induced in the vicinity of inserts in sandwich panels. Such local bending effects are associated with an increase of bending stresses in the sandwich faces and normal and shear stresses in the sandwich core. An earlier developed analytic model [Proceedings of the Sixth International Conference on Sandwich Structures (ICSS-6) (2002) 551] is adapted for the case of a sandwich panel with circular insert, with elastic properties differing from those of the core. The locally induced stresses in the faces and core due to presence of the insert are expressed via simple analytic relations (and charts) enabling an estimation of these local stresses. Finite element analysis is employed to demonstrate the applicability of the analytic model, and a good correspondence between the numerical and the analytical data is found. A study case related to marine applications, namely a circular insert in a sandwich deck panel used for mounting of a rigging fixture, is considered, and optimization of an existing design is carried out.

Impact Penetration of Sandwich Panels at Different Velocities - An Experimental Parameter Study: Part I - Parameters and Results:

Abstract: Part I of this article describes a series of tests of localized, penetrating impact on sandwich panels. The sandwich panel size was 500 500 mm2 with a thickness of 46 mm. Three types of panel configuration were tested. Penetration was carried out in quasi-static conditions and at approximately 70 and 93 m/s. Impactor mass was 1 kg with an impactor diameter of 50 mm and with three different impactor tip geometries. For each of the 27 combinations, the total energy absorption was measured, and the damage patterns are described and quantified.

Connector for a solar module

Abstract: In order to deliver the current generated by means of photovoltaic solar elements, the invention proposes a connector for a solar module that is accommodated in a connector housing and can be connected to the solar elements. The solar elements are interconnected by means of flat connecting lines and embedded in a translucid sandwich panel. The current is delivered through an opening in one of the sheets of the sandwich panel by means of springable contact elements that are in electric contact with the connecting lines of the solar elements.

Impact Penetration of Sandwich Panels at Different Velocities – An Experimental Parameter Study: Part II – Interpretation of Results and Modeling

Abstract: Based on sandwich panel penetration experiments and the observed damage patterns, as described in Part I of this article, the individual energy contributions are estimated from simple physical mode...

Sandwich panel and a method of producing a sandwich panel

Abstract: The present invention relates to a sandwich panel comprising a front face plate (2), a back face plate (3) and one or more core materials (4, 5), where said front face plate and said back face plate are interconnected by said core materials, where a number of different core inserts, and/or fasteners (51-55, 58, 59) are provided in connection to said sandwich panel, where boundaries between said core inserts and/or fasteners and said core material terminate at an angle, preferably of 90 degrees, in relation to said face plates, and/or where a number of joints, shaped by complementary surfaces of said core materials, terminate at an angle, preferably of 90 degrees, in relation to said face plates, wherein said core materials and/or said core inserts are provided with a structural grading and/or shaping of said boundaries and/or said joints. The present invention furthermore relates to a method for producing such a sandwich panel.

Similitude of sandwich panels with a ‘soft’ core in buckling

Abstract: The paper presents the similarity analysis of a sandwich unidirectional panel with a transversely flexible core under buckling loads. The governing equations are those used in the high-order analysis of sandwich panels with a ‘soft’ core. The study derives the similitude conditions in the case of external in-plane compressive loads that yield buckling of the panel with and without imperfections. In the first part, the buckling analysis is presented and it is based on the linearized version of the governing equations of the non-linear geometrical bending equations. The presentation includes an analytical proof of the applicability of similarity for the buckling of a sandwich panel with identical faces and a numerical demonstration of the response when full similarity and partial similarity exist. The effects of full and partial similarity are presented for a panel with imperfections.

A review in design and manufacturing of stainless steel sandwich panels

Abstract: stainless steel manufacturer Outokumpu Stainless Oy as well as Finnish sandwich panel manufacturers. In this article the results of the earlier mentioned R&D work in steel sandwich structures and applications is summarized from the stainless steel material point of view. The research related to design and design optimization of steel sandwich panels has been summarised by Romanoff and Kujala

Optimal Design of Steel Sandwich Panel Applications in Ships

Abstract: With the development of advanced joining techniques, such as laser welding, new structural concepts gain their ground in everyday engineering applications. Steel sandwich panels are one of these concepts, which applications are already very appealing to ship designers. Due to these reasons, it is crucial to supply the designer with the design concept that can help in obtaining best feasible structures. This paper aims to provide just that, with the presentation of a redesign of a traditionally built hoistable cardeck applying steel sandwich panels for decking. Using the approach of optimum design performance of the cardeck has been improved, significantly reducing the weight and the cost of the structure.

Fatigue Studies of Polyurethane Sandwich Structures

Abstract: The fatigue characteristics of polyurethane foam-cored (PUF) composite sandwich structures were investigated using three-point bending tests carried out according to ASTM C 393. Three types of specimens (epoxy/glass-PUF-epoxy/glass, polyester/glass-PUF-polyester/glass, and epoxy/glass-PUF-polyester/glass) were considered for investigation. Experimental results indicate that degradation of stiffness occurs due to debonding and sliding between the skin and the foam during fatigue cycles. Epoxy/glass-PUF-epoxy/glass sandwich structures exhibit higher bending strength along with higher stiffness degradation than the other two types of sandwich panels, due to higher initial fatigue loading. The lowest fatigue properties have been obtained for the polyester/glass-PUF-polyester/glass sandwich panel specimens. Better performance of the epoxy/glass-PUF-epoxy/glass sandwich panels is most likely due to the superior properties of the outer thin skins. Most of the specimens fail within the foam region and not at the skin level. This situation is possibly due to debonding between the foam and the skin. The fatigue damage development in the foam and skin has been investigated using scanning electron microscopy.

Continuously produced paper honeycomb sandwich panels for furniture applications

Abstract: Today mechanical requirements and weight targets demand a lightweight sandwich design in many application areas. The potential of honeycomb sandwich construction in furniture applications is, like in many other application areas mainly determined by the production cost of cores and panels. In the last decade the traditional honeycomb production processes for low cost paper honeycomb cores have been optimised towards concepts with a fully automated continuous in-line sandwich panel production. Sandwich selection charts, a graphical presentation of the effects of sandwich constructions on weight and cost are shown for paper honeycomb sandwich panels. This allows a transparent selection and comparison of sandwich materials for furniture applications. It can be shown that a paper honeycomb sandwich panel can offer cost savings in comparison to uniform chipboard panels.

Stability of lightweight structural sandwich panels exposed to fire

Abstract: Sandwich panels comprising thin flat metal faces and a lightweight structural core are increasingly used as walls and ceilings in buildings where their long-span capabilities, high thermal insulation, clean design, rapid installation and low maintenance often make them the preferred choice of designers and building owners. The fire performance of sandwich panels can be excellent if the correct core material is used and, importantly, if the metal facings are adequately restrained. For example, fire resistance in excess of 2 h can be easily achieved using panels with sheet steel faces and a non-combustible rock wool core. Where sandwich panels are used in cold stores there is the potential problem of cold-bridging between the facings wherever there is a metallic through-fixing, and this has led to designs which work well in normal conditions but allow panels to collapse very early when exposed to fire because the facings are not tied back to the supporting structure. Such collapse is a fire hazard to fire-fighters as proven in the 1993 fire in the Sun Valley poultry factory in Hereford, United Kingdom in which two firemen lost their lives. The paper describes what can happen if panel facings are not mechanically restrained with steel fastenings. It then introduces a fire safety engineering method for assessing the stability of ceiling sandwich panels exposed to fire. The method assumes that the ends of panels are restrained and the panel behaves as a catenary after delamination. The paper quantifies the variation of catenary force as fire develops and takes account of the initial beneficial sag which is present at the time of delamination. The method is currently being considered in the work of European committee CEN TC 127 on the development of rules for extended applications for construction products.

A structural element

Abstract: The invention resides in a structural element comprising a plurality of fibre composite sandwich panels, each sandwich panel having a pair of fibre composite skins with structural core material located there between; the plurality of fibre composite sandwich panels being adhered together; two planar, fibre composite joiners; each of the joiners having a width that is longer than the width of the fibre composite sandwich panels; the fibre composite joiners being adhered to different composite fibre skins of different composite sandwich panels; and at least one end member located adjacent at least one end of the plurality of fibre composite sandwich panels; the at least one end member being adhered to the fibre composite sandwich panels and the two planar fibre composite joiners.

Multisheet sandwich panel using superplastic forming and adhesive bonding

Abstract: We combine superplastic forming (SPF) with adhesive bonding (AB) to produce quality multisheet sandwich panel structures, especially those using a superplastic aluminum alloy, such as Al 2004, Al 8090, or Al 1570. We produce the parts with improved energy efficiency and at lower cost. We heat the multisheet pack having an adhesive, preferably a polyimide, between the core sheets and the face sheets to its superplastic forming range. Then, we superplastically form the pack to define adhesive bonds between the sheets in the core and between the core and the face sheets with the flowing adhesive. Finally, we cool the formed pack below the superplastic range to set the adhesive.

High-Order Bending Analysis of Unidirectional Curved ‘‘Soft’’ Sandwich Panels with Disbonds and Slipping Layers

Abstract: The bending behavior of unidirectional singly curved sandwich panels with a ‘‘soft’’ core and delaminated (debonded) zones or slipping layers is described herein. The delaminated zone is assumed to exist through the width of the panels, and is in the form of an interfacial debonded zone at one of the face–core interfaces, thus subdividing the length of the panel into three zones, i.e. two fully bonded zones and one that is debonded (delaminated). The formulation uses an interfacial spring description, i.e. distributed shear and radial normal springs at the face–core interfaces, to model the effects of the slipping layers and the various delaminated (debonded) zones. The formulation is based on a closed-form high-order approach (HSAPT) that incorporates the high-order effects of the ‘‘soft’’ core. The variational approach is used to derive the governing equations along with the general explicit boundary and continuity conditions. A typical curved sandwich panel with an inner or an edge delamination, with o...

Quality and costs analysis of laser welded all steel sandwich panels

Abstract: Laser welding is a fast and flexible way to manufacture all steel sandwich panels. Economically the most feasible solution is often to weld as large panels as possible. In corrugated core all steel sandwich panel applications the effect of an air gap in welding is difficult to eliminate when welding large panels. A system for welding large panels with a laser is often considered to be complicated and expensive. The processibility of large panels with specified core types was estimated by welding large all steel sandwich panels with two different core types. Materials used were low-carbon steel DC01 and stainless steel ASTM 304 with sheet thickness from 0.5 to 1.5 mm. The panels were welded with a 6 kW CO2 laser. The manufacturing of large steel panels was possible with acceptable weld quality (EN-ISO 13919-1). The total flatness of the panels was better than 11.3 mm, depending on the manufacturing procedure, core type, and material. Total manufacturing costs of high power CO2, Nd:yttrium–aluminum–garnet a...

Evaluation of gfrp deck panel for the o'fallon park bridge

Abstract: Under the Innovative Bridge Research and Construction (IBRC) program of the Federal Highway Administration (FHWA), the City and County of Denver in cooperation with the Colorado Department of Transportation (CDOT) and FHWA built a bridge with a glass fiber reinforced polymer (GFRP) deck in O'Fallon Park, which is located west of the City of Denver. One of the main objectives of this project was to investigate the feasibility of using FRP decks for highway bridges. Hence, the FRP deck in the O'Fallon Park bridge was designed to have a configuration similar to a highway bridge deck. The GFRP deck has a sandwich construction with top and bottom faces and a honeycomb core. Because of the lack of standard design provisions and manufacturing techniques for GFRP deck C panels, studies have been conducted at the University of Colorado at Boulder to evaluate the design proposed by the manufacturer, and the load-carrying capacity and long-term performance of the selected panels as part of the IBRC program. This study has shown that the design of the GFRP deck is adequate according to the provisions of the City and County of Denver. The deck has a factor of safety of five against failure. The deck also satisfies the deflection limits stipulated in the design provisions. However, the tests and the analyses have indicated that the material orthotropy of the panel and the localized bending effect caused by the soft core can reduce the effective bending width by 25% compared to a homogenous isotropic panel. Furthermore, this and past studies have shown that the governing failure mode of this type of sandwich panel is the delamination of the upper face from the core and that there is a large scatter of the interface shear strength among the test specimens. Hence, this should be a major consideration in design.

Ultimate Strength of Precast Concrete Sandwich Panel with Opening Under Axial Load

Abstract: A precast sandwich panel which is being developed as a building system consists of a single layer of insulation sandwiched between two layers of reinforced concrete. At present, an equation to predict the ultimate strength of precast concrete sandwich wall panel with opening, to the best of authors’ knowledge, is not available. This paper reports a research effort to determine the suitability of the load equations developed by earlier researchers for thin reinforced concrete solid wall with opening when used to estimate the ultimate load of precast concrete sandwich wall panel with opening. Nine sandwich panels with different window and door opening combination were prepared and tested under uniformly distributed load. The load was applied and increased in stages till failure. At each stage of the load, deflection gauges and strain gauges reading were recorded. The development of cracks was also monitored. The experimental ultimate loads of precast concrete sandwich wall panels with opening tested in the laboratory were compared with and found close to the theoretical values derived from the equation proposed by Saheb and Desayi for ordinary precast concrete wall panels with opening.

Partly filled honeycomb panel

Abstract: A sandwich panel (10) includes a honeycomb core (12) of a plurality of cells (20). A first skin (14) is adhered to a first surface of the honeycomb core (12) with an adhesive. A second skin (16) is adhered to a second surface of the honeycomb core (12) with the adhesive. The plurality of cells (20) extends longitudinally between the first and second skins (14, 16). The first and second skins (14, 16) adhere to the honeycomb core (12) to form a sandwich panel (10) having a surface area of at least 2.25 square feet. A foam fill (18) is disposed within the cells (20) of the honeycomb core (12). The foam fill (18) and the honeycomb core (12) define a first gap region (22) proximate to the first skin (14) and a second gap region (22) proximate to the second skin (16).

Sandwich panel for heating, cooling or for use as collector comprises central support to whose surfaces cover layers are applied, grooves in surface allowing pipes to be mounted below cover layer

Abstract: Sandwich panel for heating, cooling or for use as a collector comprises a central support (1) to whose surfaces (11, 12) cover layers (22, 33) are applied. Grooves (13) in the surface allow pipes (33) to be mounted below the cover layer. These are slightly deeper than the diameter of the pipes. Independent claims are included for: (a) a method for making the panel by pressing cover layers on to the adhesive-coated surfaces of the support; and (b) use of the panel in roofs or facades in which the outside of the panel acts as a solar collector and the inner surface as part of a heating or cooling system.

Double-side colour-steel sandwich plate

Abstract: The utility model discloses a double-sided color steel sandwich panel, the partition slab consists of a two layers color steel plies and a sandwich ply agglutinated between the two layers of color steel plies, the color steel ply is a color steel sheet ply constructs of an armor plate processed through some times of paint baking process, the sandwich ply is agglutinated between the two layers of color steel plies, is a polystyrene foam plastic ply mixed with fire retardant, a film of razor-thin bond ply is formed by a bond between the sandwich ply and color steel plate ply, the bond ply is a chemical material of premixed polyether polyol, and isocyanate, because of the construction features, the fire retardant polystyrene foam plastic are of inner core, lightweight, beautiful and elegant, has good heat-keeping effect, besides, the utility model has the advantages of sound and heat insulation, damp-proof, corrosion resistance, as well as anti-press, high intensity and good stability due to the structure of two layers of color steel plies agglutinated together with sandwich ply.