Showing papers on "Sandwich-structured composite published in 1971"

Further study of composite laminates under cylindrical bending.

Abstract: In a series of three papers [1,2,3], the range of applicability of classical laminated plate theory (CPT) in describing the response of composite laminates under static bending has been examined. Briefly, exact solutions within the framework of linear elasticity theory were developed and compared to the respective solutions governed by CPT [4,5,6]. Numerical data calculated based on simple harmonic load distributions have indicated rather wide discrepancy between the two solutions for laminates having low span-to-depth ratios. At high aspect ratios however, the CPT solution is in good agreement with the elasticity solution.

Structural light-weight panel of high strength,having theral insulation properties and enclosures formed thereby

Abstract: A structural light-weight panel of high strength, having thermal insulation properties that render the panel particularly suitable for cryogenic and elevated temperature applications. The panel is constituted by a composite core bonded to a carrier membrane or laminated to facing skins, the core including at least one layer formed by a series of balsa beams in spaced relation, the spacing between the beams being filled with slabs of an insulating material such as rigid foam plastic material whose k-factor is similar to that of balsa, whereby the overall thermal insulating characteristics of the composite core are effectively equivalent to that of a homogeneous core composed entirely of foam plastic material, whereas the structural characteristics of the composite core are far superior thereto. The panels are useable as liners for structural enclosures for the storage of fluids at cryogenic to high temperatures.

Sandwich panel construction

Abstract: A SANDWICH PANEL CONSTRUCTION COMPRISING TWO INDEPENDENT OUTER LAYERS ATTACHED TO OPPOSITE SIDES OF A FOAMED METAL CORE, SAID CORE HAVING REINFORCING ELEMENTS THEREIN. COMPARED TO SANDWICH PANEL CONSTRUCTION HAVING NO REINFORCING ELEMENTS, THE PRESENT CONSTRUCTION HAS SUBSTANTIALLY IMPROVED RESISTANCE TO DEFORMATION.

Foamed core sandwich construction

Abstract: A SANDWICH PANEL CONSTRUCTION COMPRISING TWO INDEPENDENT OUTER SHEETS ATTACHED TO OPPOSITE SIDES OF A FOAMED METAL CORE. COMPARED TO KNOWN SANDWICH PANEL CONSTRUCTION, THE PRESENT PANELS ARE LIGHTWEIGHT, DIMENSIONALLY STABLE, STRONG, FIRE RESISTANT AND RESISTANT TO DETERIORATION CAUSED BY ATMOSPHERIC CONDITIONS AND ORDINARY AGING. D R A W I N G

Minimum weight web-core sandwich panels subjected to uniaxial compression.

Abstract: Analytical methods are developed by which web-core sandwich panels can be designed with minimum weight while retaining their structural integrity (i.e., structurally optimum) for a given load index, panel length and width, and specified face and web materials. These methods also provide a means for rational material selection through the comparison of weights of the minimum weight construction for various material system as a function of load index, and an assessment of weight penalties associated with the use of commercially available thicknesses. The methods account for both isotropic and orthotropic face and core material as well as various boundary conditions. Numerical results clearly show the weight savings associated with the use of second generation composite materialssuch as boron-epoxy and graphite-epoxy.

Method for manufacturing foam sandwich panels

Abstract: In order to provide rapid production of foam sandwich panels of the type utilized in building structures, an upright open top press, which clasps semi-rigid outer panels in spaced relationship, is filled with a quick rising foam by injecting the foam in repetitive horizontal layers using a specially configured gun. The press consists of three essential sections: the two outer members which contain the panel being prepared in the proper configuration without bulges, and a central, removable member which functions to define the bottom and ends of the foam injected between the semi-rigid panels. One of the outer members is mounted on rails to permit ready set up and withdrawal of the press and completed panels. The two outer members of the press are held together during the panel-forming operation by a plurality of snap-over clamps spaced about the periphery.

Composite sandwich panel type construction

Abstract: A COMPOSITE SANDWICH PANEL TYPE CONSTRUCTION COMPRISING TWO INDEPENDENT OUTER LAYERS ATTACHED TO OPPOSITE SIDES OF FOAMED METAL CORE, SAID CORE HAVING Z-SHAPED REINFORCING ELEMENTS THEREIN. A PREFERRED PANEL CONSTRUCTION HAS ONE OUTER LAYER EXTENDING AROUND SAID FOAMED METAL CORE SO AS TO SUBSTATALLY ENCASE SAID CORE, METHODS OF FABRICATING SUCH A PANEL CONSTRUCTION (1) BY CASTING SAID FOAMED ALUMINUM AROUND SAID REINFORCING ELEMENTS AND SUBSEQUENTLY ATTACHING SAID OUTER LAYERS TO THIS INTERAL METAL FOAM/REINFORCING ELEMENT CORE STRUCTURE, AND (2) BY FIRST PREPARING SAID CORE FROM INDIVIDUAL METAL FOAM PIECES WHICH ARE THEN ATTACHED TO PERFORMED Z-SHAPED REINFORCING ELEMENTS, SAID ASSEMBLED CORE STRUCTURE THEN HAVING THE OUTER LAYERS ATTACHED THERETO. COMPARED TO THE COMPOSITE SANDWICH PANEL CONSTRUCTION HAVING NO Z-SHAPED REINFORCING ELEMENTS IN SAID CORE, THE PRESENT CONSTRUCTION HAS SUBSTANTIALLY IMPROVED STRENGTH.

Buckling of Multilayer Plates by Finite Elements

Abstract: A method for determining the critical in-plane stresses for multilayer sandwich plates is developed. Stress funcitons are assumed in the finite element development of the stiffness of a multilayer plate element. A stiffness modifying matrix is then used to formulate an eigenvalue problem, which when solved yields the critical in-plane stresses. This procedure facilitates the solution of multilayer plates of varying boundary conditions and in-plane stress distribution.

Supersonic flutter of sandwich panels: effects of face sheet bending stiffness, rotary inertia, and orthotropic core shear stiffnesses

Abstract: Numerical analysis of supersonic flutter of flat rectangular, biaxilly stressed sandwich panels

Multi-ply, metal-clad sandwich panels

Abstract: A multi-ply metal-plated sandwich panel made up of: 1. A FIRST (OUTER) PLY OF A CORROSION-RESISTANT METAL HAVING A THICKNESS OF FROM 0.05 TO 1 MM; 2. A SECOND (INNER) PLY OF AN ETHYLENE COPOLYMER CONTAINING CARBOXYL GROUPS HAVING A THICKNESS OF 0.01 TO 0.4 MM AS A HOTMELT ADHESIVE; 3. A THIRD (INNER) PLY OF A SPECIAL ADHESION PROMOTER HAVING A THICKNESS OF 0.01 TO 0.4 MM; 4. A FOURTH (INNER) PLY OF A THERMOPLASTIC HAVING A THICKNESS OF 2 TO 20 MM; 5. A FIFTH (INNER) PLY OF A SPECIAL ADHESION PROMOTER HAVING A THICKNESS OF 0.01 TO 0.4 MM; 6. A SIXTH (INNER) PLY OF AN ETHYLENE COPOLYMER CONTAINING CARBOXYL GROUPS HAVING A THICKNESS OF 0.01 TO 0.4 MM AS A HOTMELT ADHESIVE; AND 7. A SEVENTH (OUTER) PLY OF A CORROSION-RESISTANT METAL HAVING A THICKNESS OF 0.05 TO 1 MM.

Thermal conductivity of honeycomb sandwich panels for space applications

Abstract: The thermal conductivity of a honeycomb sandwich panel was mesisured in the three characteristic directions. The measurements were carried out in the NLR space simulation chamber. The results are in good agreement with values calculated for a simplified model.

Effects of Rotary Inertia on the Supersonic Flutter of Sandwich Panels

Abstract: A theoretical analysis is presented for the supersonic flutter of a simply-supported isotropic sandwich panel. The aerodynamic loading is described by a static approximation valid for a wide range of Mach number. Small deflection theory for sandwich plates which considers transverse shear deformations and rotary inertia in addition to bending is used. The purpose of this study is to demonstrate the effect of the rotary inertia parameter on the critical flutter speed of simply-suppor ted panels. Previous investigators have neglected this effect and results obtained are of an anomalous nature for certain plate parameters. The effect of such plate parameters as rotary inertia, transverse shear, and midplane stress resultants on the critical flutter speed are presented in graphical form.

Elastic Stress Waves in Layered Composite Materials

Abstract: In [1], a theory is proposed by Chou and Wang for the calculation of elastic wave front speeds in unidirectional composite materials. A basic assumption employed in the theory states that after a brief initial transient period, the wave front attains a steady state and propagates with unchanging wave shape. The purpose of this paper is to present a preliminary experimental justification of this assumption. Although the results are not conclusive, they do show that the wave front is approaching a steady state. This paper also demonstrates that the photoelastic method is suitable for the study of wave propagation in composite materials. High speed photography and dynamic photoelasticity are used for testing a photoelastic composite model. The test specimen, shown in Figure 1, consists of two bonded plastic reference plates of PSM-IB* and S-16°°, mounted opposite to

Minimum Weight Design of Orthotropic Sandwich Panels Loaded in Compression and Shear

Abstract: : The purpose of the report is the determination of the minimum weight configuration of rectangular orthotropic sandwich panels with fibre-reinforced plastic faces designed to meet specified requirements with regard to strength, stability, in-plane stiffness and minimum feasible thicknesses of core and faces. The design specifications are assumed to comprise an arbitrary number of different states of loading acting successively on the panel. Each state of loading may consist of either unixial compression or tension, pure shear or a combination of such loads. In order to investigate the weight-efficiency of different reinforcing materials, optimum configurations are numerically determined for long sandwich panels with simply supported edges and with faces reinforced by bidirectional glass-fibre fabric, unwoven E-glass fibres and boron fibres. The weight of such panels is compared with that of panels having faces of aluminium for the purpose of studying the advantages or disadvantages of aluminium and fibre-reinforced plastics as design materials in the light of different design requirements. (Author)

Stiffness Matrix for Sandwich Folded Plates

Abstract: Reissner’s equations for isotropic sandwich plates are used to derive a set of stiffness coefficients which, in conjunction with a stiffness method, can be used to analyze folded plate structures made from sandwich panels. The derivation results in a stiffness matrix which can be used directly in the stiffness formulation outlined by Scordelis for homogeneous folded plates.

Face Wrinkling of Sandwich Plates and Cylinders

Abstract: Face wrinkling of sandwich plates and cylinders is treated as a problem of local stability of a sandwich face sheet resting on an elastic foundation. The core is replaced by an equivalent spring determined by the use of an energy principle. Formulas are derived and curves are presented to illustrate the buckling behavior of the structure. The results of the study demonstrate that plate action does increase the face wrinkling strength of the sandwich structure. The effect of curvature of sandwich cylinders is shown to be negligible when the radius-to-face thickness ratio is large, as is usually the case.

Strength and stiffness of sandwich panels under transverse loading

Abstract: THIS paper describes work done to translate the theory of Structural Sandwich Panel Design into a form in which it could be used for rapid estimation in a design office.

Dynamic Stability of Circular Cylindrical Sandwich Panels

Abstract: A theoretical study of the dynamic stability of simply supported sandwich plates and circular cylindrical sandwich panels with dissimilar face-sheets and orthotropic cores is presented. The uniformly distributed periodic edge loads consist of steady components and oscillating components which are impulsive or vary according to an arbitrary piecewise constant law. It was observed that stable regions exist when the steady component of the applied load exceeds the static buckling load. For the particular combination of parameters associated with these regions the oscillating component of the load has a stabilizing effect on the structure. It was further observed that the mathematical structure of the equations governing the dynamic stability of simply supported sandwich plates and circular cylindrical sandwich panels is the same as that for the corresponding simply supported, homogeneous plates and panels, and a complete analogy exists between them.

On the design of fiberglass reinforced plastic ship hull structures

Abstract: Basic problems on the design of fiberglass reinforced plastic (FRP) ship hull structures are considered. The design procedures of FRP structures are considerably different from the conventional method of metal structures. FRP is a kind of composite materials and is inherently heterogeneous anisotropic, and the FRP structural design is closely connected with the FRP material design (in particular, the lamination design of FRP). Composite constructions such as stiffened panels and sandwich panels are important in FRP structural design, in order to compensate the low rigidity of FRP (one of the main faults of the material). In part I, the rigidity of FRP laminated plates (using chopped strand mats and woven rovings) are considered on the basis of classical theory of anisotropic laminates. Further, the large deflections of orthotropic membranes are considered by the energy method taking into consideration the initial small deflections, and compared with the hydrostatic pressure test results of FRP laminates. In part II, the rigidity and strength of FRP sandwich constructions with FRP faces and plastic foam core are discussed. Basic equations of rotation angles and deflection of sandwich plates with orthotropic membrane faces under lateral load are derived by the application of Cheng's theory (orthotropic core). The closed-form solutions are given in the case of simply supported edges and the finite difference solutions are given in the case of fixed edges. The latter are compared with the hydrostatic pressure test results of FRP sandwich panels. Typical examples of shear fracture modes of core after test are shown and discussed. Further, the bending behavior of FRP sandwich beams cut from the panels are discussed experimentally. In part III, seven kinds of simplified FRP composite structural models are fabricated and tested, in order to grasp the complex behavior of the actual FRP composite constructions. The bending behavior of these models are discussed from the view-point of the structural effectiveness. Simplified analyses are made on the effects of the shear deflection, the incomplete interaction of the stiffeners and the main beam, and the fall of effectiveness of the compression-side flange due to local deflections. Finally, the test results of these models are compared and discussed, defining the structural efficiency as the ratio of the so-called structural Young's modulus and that of the material.