Showing papers on "Sandwich panel published in 2001"

Truss core sandwich panels and methods for making same

Abstract: A structural material includes a plurality of discrete, interwoven wires disposed between and fastened to two solid face sheets. Each of the plurality of wires further includes at least two points of contact with each of the two face sheets. Methods for fabricating the aforementioned structural material include an automated methodology for fabricating a relatively inexpensive truss core sandwich panel.

Noise reduction sandwich panel, notably for aircraft turbojet engine

Abstract: Noise reduction sandwich panel, notably for an aircraft turbojet engine. In order to produce a noise reduction sandwich panel having a structure with two degrees of freedom, inserted separative components (20) are placed into the hexagonal cells (16) of the unique waffle core of the panel. More specifically, the separative components (20) have an substantially circular external peripheral edge, which allows them to be easily assembled, in spite of the deformations of the walls (18) of the cells (16) due to manufacturing tolerances and to the optional forming of the waffle core. Advantageously, several separative components (20) are supported by a same positioning unit (22), which then allows relative displacement between the separative components.

Fiber-reinforced sandwich panel

Abstract: The present invention may be embodied in a sandwich panel having first and second face panels each having a first predetermined thickness and being formed of a fiber-reinforced cementitious material. The sandwich panel further includes support frame for supporting the first and second face panels in a spaced apart configuration. The support frame is formed of a fiber-reinforced cementitious material that is continuous with the cementitious material of the first and second face panels. Blocks of rigid insulation are embedded in the sandwich panel for defining a structure of the support frame.

Composite, Grid-Stiffened Panel Design for Post Buckling Using Hypersizer (Trademark)

Abstract: : Due to weight and cost goals. a grid-stiffened panel concept is being used for redesign of a structural component on the Minotaur OSP space launch vehicle. By designing the structural panels to carry operational loads past the point of initial buckling (local post- buckling). the resulting grid stiffened panel concept is lighter and 300- less costly to manufacture than other design candidates such as the existing honeycomb sandwich panel concept flown today. During June 2001 in Seattle. Boeing performed a structural certification experiment of a composite, grid stiffened, cylindrical panel loaded in axial compression. Pretest predictions were made for linear elastic (bifurcation) buckling, and non-linear post buckling. The tools used for pretest analysis were HyperSizer(Registered). and the FEM based tools MSC/NASTRAN(TradeMade) and STAGS(TradeMade). Local buckling of the facesheet triangular shaped skin pocket occurred at a load of around 230 (lb/in). The test panel was able to sustain considerable additional loading. with post buckling failure occurring at 1320 (lb/in). The HyperSizer post buckling pretest prediction was 1300 (lb/in), the STAGS pretest prediction was 1250 (lb/in), and the MSC/NASTRAN pretest prediction ranged from 1425 to 2000 (lb/in). HyperSizer's implementation of local post buckling based on an effective width approach is presented.

Prediction of Natural Frequencies of a Sandwich Panel Using Thick Plate Theory

Abstract: The vibration of a sandwich panel with two identical isotropic facesheets and an orthotropic core was studied. The governing partial differential equation was derived using a variational principle. Linear shear theory was employed to describe the transverse deformation of the panel, and the rotational effect was taken into consideration. The natural frequencies of a rectangular sandwich panel can be predicted on the basis of the proposed analytical model. Results from the proposed model were compared with those from thin plate theory. The effects of the structural and material parameters such as core anisotropy, core density, and facesheet thickness on natural frequencies were discussed.

Analysis and Parametric Study of Non-Circular Pressurized Sandwich Fuselage Cross Section Using a High-Order Sandwich Theory Formulation

Abstract: Results obtained as part of a design study regarding a non-circular pressurized sandwich fuselage cross section are presented. The originating problem is associated with preliminary studies for the “Global Range Transport” envisaged by the “New World Vistas” program of the United States Air Force. The modeling and analysis is conducted using a high-order sandwich theory formulation in which the elastic response of each face laminate is accounted for, including bending-stretching coupling, and including the transverse flexibility of the core material. The paper includes a presentation of the high-order sandwich theory approach adopted for the analysis of the fuselage section, including the formulations for flat and curved sandwich panels. The paper is concluded by presentation of the results of a parametric study, which includes the effects on the structural response of varying the sandwich panel mid-plane asymmetry, the core properties, and the radius of curvature of the fuselage cross section corners.

Honeycomb sandwich panel

Abstract: In a honeycomb sandwich panel having a honeycomb core, and a front surface layer and a rear surface layer sandwiching the honeycomb core on its upper and lower surfaces, at least one of the front surface layer and the rear surface layer is made of a fiber reinforced plastic using a phenolic resin as a matrix.

Center Notch Flexure Sandwich Geometry for Characterizing Skin-Core Adhesion in Thin-Skinned Sandwich Structures

Abstract: The fracture properties of a number of sandwich structures have been investigated using a simple three point bend test geometry. The center notch flexure sandwich (CNFS) test involves loading the lower skin of the sandwich structure and propagating a central crack along the lower skin-core interface. A finite element analysis has been used to determine the crack tip loading conditions as a function of crack length and mechanical properties of the sandwich panel. The analysis agrees well with strain energy release rate data obtained via experiment, and shows the CNFS test to be predominantly mode I. The CNFS technique has been used to characterize the interfacial fracture properties of several foam, balsa, and honeycomb-based sandwich structures similar to those currently used in the marine and aerospace industries. Experimentally-determined values for interfacial fracture energy varied between approximately 170 J/m 2 for a glass fiber reinforced polyester/linear PVC system and 2750 J/m 2 for a glass fiber reinforced sandwich system based on a Nomex honeycomb core. The fracture toughness values obtained through the CNFS test agreed well with those values obtained via two different test methods. The J integral has been proposed as a fracture criterion for CNFS specimens that do not behave in a linear elastic manner; initial findings suggest this fracture criterion is applicable to CNFS specimens.

Dry-cast hollowcore concrete sandwich panels

Abstract: A concrete sandwich panel (10) is provided with a first dry-cast hollowcore concrete layer (12) having pre-stressing strands (24), and a second concrete layer (14), and an insulation layer (16)sandwiched therebetween. The insulation layer (16) includes pre- formed holes (26). A tool is used to form holes in the first concrete layer (12) aligned with the insulation holes (26). Adhesive (40) is injected into the concrete holes (28). The adhesive (40), when cured, locks the connector (18) in the hollowcore concrete layer (14). The upper concrete layer (12) is cast over the insulation layer (16) so as to embed the upper ends of the connectors (18). The plasticity of the upper concrete layer (12), which may result from vibration energy input to low-slump concrete, allows the concrete to consolidate around the upper ends of the connectors (18). When the concrete layers (12, 14) cure, the connectors tie the layers together to preclude excessive shear displacement between the concrete.

High-Order Analysis of Unidirectional Sandwich Panels with Flat and Generally Curved Faces and a “Soft” Core

Abstract: The bending behavior of a unidirectional sandwich panel with flat and generally curved faces and a flexible core in the vertical direction is investigated. The studied panels consist of an upper flat face sheet, a core of variable thickness, and a lower face sheet that can take any geometrical layout described by an analytical function. The core is assumed a two-dimensional elastic medium with shear and transverse vertical rigidities only, and the face sheets are considered as membrane and bending members made of metallic or composite materials. The term unidirectional refers here either to a beam (narrow panel) or to a wide beam (panel) undergoing a cylindrical bending. The field equations and the boundary conditions are derived via the variational principle of the virtual work and transformed from the local polar coordinate system of the curved face into the global Cartesian one. Higher order effects due to flexibility of the core in the form of nonlinear deformation fields are incorporated in the propo...

Application of decohesive model with mixed damage scale in fracture analysis of composite materials

Abstract: A decohesive model using a mixed damage scale and using the total fracture energy to simulate the fracture process of composite materials has been developed in this article. The model assumes a bilinear interfacial decohesion function and is incorporated into an interface finite element developed as a user subroutine in the commercial FEA package ABAQUS. In comparison with traditional numerical methods in fracture mechanics, this approach can automatically predict the failure load, crack path and the residual stiffness of bodies undergoing the fracture process. Applications given in this paper are simulation of a typical fracture test with a double cantilever beam (DCB) specimen; modelling a stiffened composite laminated panel under four-point bending and modelling a repaired composite sandwich panel under four-point bending. Good correlation was seen between modelling predictions and experimental results.

Embedded heat pipe sandwich panel constructed using dissimilar materials

Abstract: An embedded heat pipe sandwich panel having components made using dissimilar materials is described. An exemplary embedded heat pipe sandwich panel comprises graphite faceskins secured to aluminum honeycomb core using traditional film adhesives. One or more aluminum heat pipes are embedded in the sandwich panel and thermally coupled to the faceskins using a high thermal conductivity gasket material disposed between the panel faceskins and the heat pipes.

Modeling Low-Velocity Impact Damage of Composite Sandwich Panels

Abstract: Analytical solutions for the low-velocity impact damage of composite sandwich panels are found by considering systems of discrete masses, springs and constant-force dashpots. Equivalent spring and dashpot forces for the sandwich panel are derived from the static load-indentation response and adjusted with dynamic material properties of the facesheet and core. Predictions of the maximum impact force are about 15% higher than experimental values, which is the same order of accuracy that is obtained from the static load-indentation analysis. Damage initiation due to tensile failure by hemispherical-nose shape projectiles and shear failure by blunt projectiles are examined. Predicted tensile and shear failure loads are about 20% higher than experimental results.

Simulation of the creep expansion of porous sandwich structures

Abstract: Recently developed sandwich structures consist of a porous metal core sandwiched between two fully dense face sheets. These structures are produced by pressurizing a metal powder compact with an inert gas prior to consolidation by hot isostatic pressing (“hipping”). After consolidating and hot rolling the compact to a sheet form, a high-temperature annealing step is used to expand the internally pressurized gas-filled micropores. This expansion results in a porous core sandwich structure with integrally bonded face sheets. Recent experimental studies[1] with a Ti-6Al-4V porous core sandwich have indicated that the expansion rate exhibits a maximum during thermal ramping to 920 °C but then continued to expand over many hours at a constant temperature. Significant grain growth also accompanied the expansion. A microstructure-dependent creep model has been developed for a body containing a distribution of spheroidal pores. The body’s constitutive behavior is described by microstructure-dependent creep potentials for dislocation (power law) and diffusion-accommodated grain-boundary sliding (DAGS). It has been used to simulate the expansion of Ti-6Al-4V sandwich structures subjected to thermal cycles similar to those studied experimentally. The simulated response compared well with experimental results. The model was then used to identify an attainable core porosity as a function of the initial gas pressure and initial core relative density at the completion of the expansion process step.

Plasma display device

Abstract: PROBLEM TO BE SOLVED: To provide a plasma display device which suppresses an increase of weight and space of the device to the minimum, has the strength durable for the requirements such as vibration and impact as well as improper load and has the dissipation function for the heat dissipated from a module in order to permit the use of the plasma display device in the dynamic environment. SOLUTION: A reinforcing material 15 of a sandwich panel (laminated panel) in which a honeycomb core 151 made of aluminium alloy is interposed between aluminium alloy sheets 153 is disposed on the rear face of the display module 10. The reinforcing material 15 is light in weight, at the same time, the items required for the improper load is satisfied and the heat dissipating function is retained by disposing a cooling fin 171 on the inner surface of a supporting member 17 disposed on the reinforcing material 15.

Development of H-2A launch vehicle composite interstage structure

Abstract: The Interstage structure of an H-2A launch vehicle was developed as CFRP and foam core sandwich structure by co-curing technique. In the design analysis, nonlinear buckling analysis for a sandwich panel cylinder was conducted considering the imperfection effect of the actual cylinder shape. The manufacturing process of the co-cured composite cylinder was established in various manufacturing tests. The Interstage structure was qualified by a full-scale strength test. The required cost and weight target was achieved.

Method for forming a three-dimensional construction

Abstract: The invention relates to a method for forming a three-dimensional construction from a hollow sandwich panel (1), which consists of two boards (2) which are held at a mutual distance by spacer elements (3) extending mutually parallel and lying at a mutual distance, which method consists of reducing the bending stiffness of the sandwich panel (1) by reducing the stiffness of at least one of the boards, and bending the sandwich panel (1) round an axis of curvature such that in the area of the bending an inner board with relatively small radius of curvature and an outer board with relatively large radius of curvature are created, wherein according to the invention the bending stiffness of at least one of the boards is first reduced by deforming a part of the relevant board, and the sandwich panel (1) is subsequently bent round the axis of curvature formed by the deformed board part, and wherein the axis of curvature can also be straight or curved.

Soundproofing structure of structural body using sandwich panel

Abstract: PROBLEM TO BE SOLVED: To provide a soundproofing structure of a structural body using a sandwich panel facilitating the construction, reducing manhour, the manufactur ing cost, and the weight of the whole body, and maximizing the car inside space. SOLUTION: The structural body 22 is constituted of the sandwich panel 29 having a core 28 with a lot of clearances, between two faceplates 25 and 26 so that a lightweight and highly rigid body structure is provided. A vibration damping material 27 is provided between the two faceplates near a connecting part 24 of the body structure 22 so as to suppress the vibration of a part near the connecting part of the respective faceplates. If the vibration is transmitted from an underframe 23 to the body structure 22, the vibration of the respective faceplates 25 and 26 becomes small in a large area of the body structure 22 so as to prevent the vibration of the respective faceplates 25 and 26 from being a generation source of the noise.