Showing papers on "Sandwich-structured composite published in 1988"

Cellular Solids: Structure and Properties

Abstract: 1. Introduction 2. The structure of cellular solids 3. Material properties 4. The mechanics of honeycombs 5. The mechanics of foams: basic results 6. The mechanics of foams refinements 7. Thermal, electrical and acoustic properties of foams 8. Energy absorption in cellular materials 9. The design of sandwich panels with foam cores 10. Wood 11. Cancellous bone 12. Cork 13. Sources, suppliers and property data Appendix: the linear-elasticity of anisotropic cellular solids.

Compressive Strength of Composite Sandwich Panels After Impact Damage: An Experimental and Analytical Study

Abstract: The effect of low speed impact on the compressive strength of graphite/epoxy sandwich panels was examined experimentally and analytically. Various impactor sizes and impact energy levels were used. Impact damage was found to decrease the compressive strength of panels in this investigation by up to 33%. The use of film adhesive as an interply layer was found to reduce the extent of damage and increase the residual compressive strength. A one-parameter model to predict compressive failure of impact damaged panels is presented. The theoretical predictions are in good agreement with experimental results. Some of the factors affecting the panel behavior are also discussed.

Fiber Composite Sandwich Thermostructural Behavior: Computational Simulation

Abstract: Four computational simulation methods with different levels of sophistication were used to simulate thermal behavior and structural changes of composite sandwich panels with a honeycomb core subjected to a variety of environmental effects. The models on thich these methods are based include three-dimensional finite-element modeling, three-dimensional finite-element modeling assuming a homogeneous core, laminate theory, and simple equations for predicting the equivalent properties of the honeycomb core. A procedure was developed and embedded in a composite mechanics computer code, which made it possile to conduct parametric studies to determine 'optimum' composite sandwich configurations for specific applications. The procedure was applied for the evaluation of composite sandwich behavior at the global, local, laminate, ply, and micromechanics levels when the composite sandwich is subjected to hygral, thermal, and mechanical loading environments.

Reinforced honeycomb core sandwich panels and method for making same

Abstract: The composite structural panel has bottom (24), top (26) and edge layers (28) which enclose a primary core (30). The core provides additional structural strength to the panel. The edge layer (28) forms a desired panel edge angle of approximately 20° to 45°. The primary core (36) is trimmed at an angle (46) of approximately one-half the desired edge angle to form a first pressure reaction surface (48). A peripheral core (56) is positioned on the tapered portion of the primary core (36) so that the axis of the peripheral core (56) is perpendicular to the first pressure reaction surface (48). The peripheral core is trimmed to form a second pressure reaction surface (62) beneath the edge of the panel. The structure is lightweight and resists deformation of the panel edge when the panel is cured under elevated pressure in an autoclave.

Viscoelastic sandwich plates with crossply faces

Abstract: An energy method has been used for an elastic formulation of buckling analysis of a simply supported sandwich plate with crossply faces, including the interlayer shear deformation of adhesive layers and the transverse normal and shear deformations of the core. A quasielastic method is used for the solution of viscoelastic analysis of the sandwich plate. Results of the viscoelastic buckling analysis under in‐plane loads are presented for various lay‐up sequences of face plates. Dependence of buckling load on face lay‐up sequence, adhesive bonding stiffness, load ratio, and plate geometry is examined, including the effect of change of buckling modes.

Application of ferrocement concept to low cost lightweight concrete sandwich panels

Abstract: Description de panneaux porteurs pour structures (compression, flexion) avec le noyau en beton leger et les faces en ferrociment; utilisation de cendre volante pour les deux materiaux. Proprietes mecaniques et thermiques, avec essais de flexion en laboratoires

Multi-objective optimization of acoustic sandwich panels

Abstract: In this paper the optimal acoustic design of sandwich panels is studied in a comprehensive way with an attempt to establish a methodology to assist the acoustic analysts and panel designers in making appropriate trade-offs between conflicting objectives Closed-form relationships between design objectives and design variables are obtained for panel cost and for panel loading and deflection from various mechanics models of panel response Four different objectives—Transmission Loss, Cost, Panel End-Loading, and Mid-Span Deflection—are combined to carry out the multi-objective optimization Finally, ways for the selection of the best-compromise solution are indicated

Composite material of low dielectric constant and method of producing it

Abstract: A composite material of low dielectric constant, having minute hollow spheres of insulating material dispersed in a fibrous Polytetrafluoro­ethylene. The composite material has high mechanical strength.

Of composite laminates

Abstract: Typically, the basic building block block of a composite material structural component is a

Composite material of metal and plastic

Abstract: A composite material is produced from a metal core and fiber-reinforced plastic material, in which the reinforcing fibers penetrate into and entwine around the metal core without coming into contact with the metal core Parts for aircraft and turbine construction can be made from the composite material to provide higher impact strength and rigidity at less weight as compared to metal components

Flexural response of foam-cored frp sandwich panels

Abstract: The flexural response of an FRP (fiber-reinforced plastic) foam- cored sandwich beam is predicted using several methods: a one- dimensional set of differential equations that represents the core as an elastic foundation, a two-dimentional solution for a governing bi-harmonic partial differential equation expressed as an infinite trigonometric series, and a finite-element solution using varying nodal point mesh densities. The comparative results for all three methods in predicting normal skin stresses, core shear stresses, and beam deflection are very good for relatively thick-skinned composites. The excellent correlation for the predicted deflections of the laminated beams to test data, for both "linear" and "cross- linked" sandwich core materials, demonstrates that the methods will work well for composite structural analysis.

Development of SiC Reinforced Titanium Corrugated Structures

Abstract: Silicon carbide (SiC) reinforced Ti-6Al-4V (SiC/Ti-6Al-4V) composite was used to fabricate unidirectional corrugated structural panels. Corrugated structural panels are more efficient than honeycomb sandwich panels under normal (aerodynamic) compressive loading at high load levels that permit relatively thin skins to carry high skin stresses. Elevated temperature compression tests were conducted on the corrugated panels. The results indicated that the load carrying capacity of the SiC/Ti-6Al-4V composite panel was substantially higher than that of the baseline Ti-6Al-4V structure, especially at temperatures above 538°C (1000°F), where titanium alloy properties rapidly degrade. A finite-element stress analysis was also performed to estimate the thermal stress and the mechanical stress at assumed service conditions with three different face sheet thicknesses. The results of the study indicate that the corrugated panel, consisting of SiC/Ti-6Al-4V face sheets and core, can be used for space applications where elevated temperature compressive loads caused by bending moments are critical, such as for the body structure of a reentry vehicle.

Buckling of Composite Sandwich Rectangular Panels (Grid Core

Abstract: Laminated composite sandwich panels are extensively used in many engineering indus tries. Stability studies are needed to achieve good structural performance with minimum weight. The work presented in this paper deals with the prediction of elastic buckling loads for composite sandwich rectangular panels with a grid core subjected to axial com pression. Kirchhoff-Love assumptions are used and each of the edges is considered to be clamped (C) or simply supported(S). The given panel is idealised as a homogeneous orthotropic plate whose equivalent properties are determined based on the given param eters of the panel. The boundary conditions considered are SCSC, CSCS, SCSS, CSSS, CCCC, CCCS, CCSC and CCSS. Critical buckling loads are obtained using conventional orthotropic plate theory. A large class of 0°/90°/45°/-45° lamination schemes leading to quadridirectional, tridirectional and bidirectional T300/N5208 sandwich Panals is ex amined and merit listed from buckling point of view. Results indicate that by ...

Coupling between two sandwich panels, and modular building system based thereon

Abstract: The invention relates to a coupling between two sandwich panels (1, 2), each comprising: an insulating layer (3) being covered on its one side with a first metal plate (4) and on its other side with a second metal plate (5), each of the panels (1,2) having a prismatic connecting edge (6, 7) for coupling by means of connecting means (13) another like panel (1, 2) to said connecting edge. It is a purpose of the invention to design a coupling of this type in such a way that interior ventilation and vapour transport in the space bounded by the plates is effectively stimulated, whilst nevertheless the properties as e.g. a partition of two coupled panels is not adversely affected.

Geometrically nonlinear finite element analysis of sandwich panels

Abstract: A displacement-based versatile and effective finite element analysis of sandwich panels is presented. The analysis is applicable to both small and large deflections. Allowance for the local bending stiffness of the faces is made. The procedure described is readily adapted to arbitrary laminated beams and plates. Selected example problems are given to illustrate the applicability of the formulation.

Acousto-Ultrasonic Evaluation of the Strength of Composite Material Adhesive Joints

Abstract: The aim of the present research program is to evaluate the tensile strength of adhesively bonded lap joints of glass fibre reinforced plastic (GRP) and carbon fibre reinforced plastic (CFRP) composites by using the acoustoultrasonic technique. The results show that depending upon the application for which the particular adhesive joints are to be used, one may choose a confidence level and then using the correlation curves, one may obtain the upper and lower bonds of strength values for a particular stress wave factor.

Toward In Situ Testing of the Mechanical Properties of Composite Panels

Abstract: Phase changes of flexural waves propagating in a composite panel are used to infer the mechanical properties. Experimental results for a Scotchply laminated composite are presented.

Sandwich panel for interior decoration and method of making such panel

Abstract: Sandwich panel for interior decoration having a tough surface. It can be used in particular for work tops 1 in fitted kitchens. An outer layer 2 is designed as a preformed component which contains aluminium trihydroxide bonded with cured synthetic resin. An underlayer 4 consists of a water-impervious plastic sheet material suitable for screwing firmly in place. In between there is an intermediate layer 3 based on a plastic foam material. The invention also relates to a method of making such a sandwich panel and to a method of making a panel composite from such sandwich panels.

Minimum Weight of a Sandwich Panel

Abstract: The least‐weight problem of a sandwich panel with a truncated, hollow, hexagonal core, and subjected to a given bending moment along each edge is analyzed in this paper. In order to meet the practical manufacturing requirements and be within allowable stress limits, constraints are placed on the geometrical dimensions of the structural parts of the sandwich panel as well as on the physical strength, such as the allowable stresses. Upper and lower limiting values are assigned for each of the design variables. Through the use of the penalty function, the minimization problem subjected to a set of twenty inequality constraints is changed to a sequence of unconstrained ones. The modified Fletcher‐Powell method is used by a proper choice of the penalty parameter and the reduction factor. The methodology presented here can be extended to include multiple loading conditions, bending rigidity, and shear rigidity requirements, which present no additional difficulties except to increase the number of constraints.

High-performance sandwich panels made from braided tubes

Abstract: A light weight, high-performance sandwich panel was developed using thin walled braided tubes as the core material. The panels have certain specific advantages over conventional honeycomb sandwich panels including superior skin-core bonding, integral conduit systems and self-draining thereby avoiding moisture accumulation. A short manufacturing process leads to a cost effective product. The technology of the tube production is not material-specific, so any reinforcing fiber can used in conjunction with a large number of resin systems including thermoplastic resins. The braided tubes used as the core can be produced in a wide variety of cross-sectional shapes and sizes so the panels can be designed to meet various specific functions. 6 figures, 1 table.

Optimum Design Methods for Structural Sandwich Panels

Abstract: : Structural sandwich panels are composed of two thin, stiff skins separated by a light weight core. The faces are typically strong materials such as aluminum fiber reinforced composites, while honeycombs or foams are used in the core. The separation of the faces increase the moment of inertia of the panel with minimum increase in weight. Because of this, these panels are extremely efficient in bending and are used in applications where the weight of the member is critical: aircraft, marine, and land vehicles; portable structures; construction in remote areas; roofing shells; and some types of sports equipment (e.g., modern downhill skis). In all of these, the mechanical behavior of the sandwich panel depends on the strength and stiffness of the face and the core, on the geometry of the panel (the core and face thicknesses), and on the bond strength between the faces and the core. The goal of this research is to determine the core density as well as the core and face thicknesses that minimize the weight of a sandwich panel for given structural requirements. This will improve the minimum design of structural sandwich panels in a manner not previously possible.

Sandwich panels as an efficient form of protection against dropped objects

Abstract: Norwegian legislation requires that sensitive areas of offshore oil platforms are protected against accidentally dropped objects. Typical of these is a drill collar weighing as much as 3.5t and dropped from 15m. Conventional design against such an event usually involves stiffened steel plate of large thickness, of high strength material or special quality steel, such as armour plating, and is therefore very costly. An alternative method of design and construction is described here, which is of sandwich form and uses ordinary mild steel enclosing a softwood infill. A simple design procedure is described which has been validated by both model- and full-scale tests.