Showing papers on "Sandwich panel published in 2000"

Elastic Stiffness Properties and Behavior of Truss-Core Sandwich Panel

Abstract: In this paper, a truss-core sandwich panel is introduced and its elastic properties are presented. Two thin flat sheets, separated by two inclined plates acting as the core and rigidly jointed at their ends, characterize the sandwich section. This construction form eliminates most of the attendant problems of conventional spot-welded or rivet-fastened sandwich panel construction. Advantages of the truss-core panel are discussed. The 3D sandwich panel is idealized as an equivalent 2D orthotropic thick plate continuum. Equivalent bending, twisting, and transverse shear stiffness are derived, and the influence of the relatively weak shear stiffness on the behavior is discussed. By integrating these elastic stiffness constants into closed-form solution, panel response is calculated. The calculated results, which requires significantly less computational effort, agree well with 3D finite-element analysis. Comparisons of stiffnesses and deflections with the corresponding responses of conventional sandwich construction are provided. This study indicates that the truss-core sandwich panel performs better due to its inherently higher flexural resistance per unit weight.

Sandwich Panel Design Using Aluminum Alloy Foam

Abstract: Metal foams may replace polymer foams in applications where multi-functionality is important. For example it acts as a structural component in a sandwich panel but also as a cooling system or acoustic damper. Associated with sandwich panel geometry and change in loading one observes three failure modes: face sheet yield, core shearing and indentation under the loading roller.

Perforation of honeycomb sandwich plates by projectiles

Abstract: An analytical solution for the ballistic limit of a honeycomb plate subjected to normal impact by blunt and spherical projectiles is presented. The solution involves a three-stage, perforation process that results in complete perforation of the sandwich. Stages 1–3 describe perforation of the top facesheet, honeycomb core, and bottom facesheet, respectively. Residual velocities in Stages 1 and 2 are found from energy balances between each stage. The plastic work dissipated in deformation and fracture at each stage is approximated from the solution of the previous stage. Shear forces are transmitted in the bond between facesheets and honeycomb core. The predicted ballistic limits are found to be within 5% of the measured ballistic limits for sandwich plates perforated by the blunt and spherical projectiles. The lateral extent and deformation of the damaged facesheets are also found to be within 34 and 51% of limited test results, respectively. It has also been found that most of the work is dissipated in perforation of the bottom facesheet during impact. The work to perforate the bottom facesheet by the blunt and spherical projectiles accounts for 63–85 and 55% of the initial kinetic energy, respectively. Therefore, the perforation resistance of the bottom facesheet, rather than the top facesheet or honeycomb core, would be an important parameter in determining the perforation resistance of the entire sandwich panel.

Panels utilizing a precured reinforced core and method of manufacturing the same

Abstract: A mass transit flooring assembly including a plurality of sandwich panels. The sandwich panels ( 30 ) include a top skin ( 54 ), a bottom skin ( 58 ), a perimeter defining closeout ( 46 ), and a core ( 50 ) between the top ( 54 ) and bottom skin ( 58 ) and within the closeout parameter ( 46 ). The closeout ( 46 ) includes mating surfaces used to connect adjacent panels. The core is a precured reinforced core including a plurality of phenolic ribs and foam strips positioned in an alternating fashion. The precured core is manufactured by impregnating a layer of fabric with phenolic resin between two foam cores and stacking in a similar alternating fashion to create a bun. After the bun is cured at a constant pressure and temperature and cooled, the bun is cut along a plane perpendicular to the plane of the layers to provide a precured reinforced core panel ready to be inserted as a core in a sandwich panel.

Structural sandwich panels and method of manufacture of structural sandwich panels

Abstract: Rigid structural members, profiles, joints, and forms added to structural sandwich panels to provide higher strength, integral joining joint, and single facing sheet manufacturing. Facing sheets ( 20 ) and ( 22 ), rigid structural members ( 24 ) and ( 26 ), latch side and pin side cam-locks ( 34 ) and ( 32 ), fabricated wire truss assembly ( 48 ), and rigid structural headers ( 28 ) and ( 30 ) and an integrated top plate ( 29 ) are positioned into containment form assembly ( 58 ) in the proper position. Facing sheets ( 20 ) and ( 22 ) are placed in position in the containment form assembly ( 58 ) forming a structural sandwich panel assembly. A foam resin core material ( 40 ) is injected into the structural sandwich panel assembly and allowed to cure. The resultant structural sandwich panel includes rigid structural members ( 24 ) and ( 26 ) and elongated recesses ( 36 ) and ( 38 ) which also form a joint for joining abutting structural sandwich panels together and cam-locks ( 32 ) and ( 34 ) used to secure adjoining panels together. Comer and angle panels have a comer rigid structural assembly ( 44 ).

Method of manufacturing a sandwich panel, made of composite material, and a panel thereby obtained

Abstract: In order to manufacture a sandwich panel using the RTM technique, a stack comprising a core ( 10 ) with open cells, a film ( 12 ) of intumescent material covering each of the faces of the core ( 10 ), a dry barrier fabric ( 14 ) covering each of the films ( 12 ) and an overlay of dry fibers ( 16 ) covering each of the barrier fabrics is placed in a mold. During polymerization of the films ( 12 ), pressurization of the mold and the presence of the barrier fabrics ( 14 ) prevent penetration of the foam into the overlays ( 16 ). The resin is then injected into the mold and then polymerized, without danger of penetration into the cells of the core ( 10 ).

Failure Modes and Load Transfer in Sandwich T-Joints

Abstract: Various T-joints of composite sandwich panels were investigated. The corresponding modes of failure at the joint were identified. The key modes of failure include debonding between the two sandwich components to be joined, debonding between the attachment and the sandwich panel, and cracking in the core of the sandwich. A new type of T-joint incorporating an aluminum U-channel in the web sandwich was found to provide much improvement over the conventional circular fillet T-joint. Two types of bolted joints were also studied to investigate the effectiveness of using bolts for suppressing debonding at the joint. It was shown that using bolts in a circular fillet joint could cause early failure in the core and would not help much to increase the ultimate joint strength. The experimental failure modes of the tested joints were explained with the help of FE analysis.

Sandwich panel made of a composite material and production method

Abstract: A sandwich panel made of a composite material with acoustical attenuation for a wall and/or self-supporting covering, more particularly for doubling the bulkheads or cabin walls of aircraft, and including an alveolar structural core (14) especially a honeycomb core, and two skins (12, 16) disposed and rendered integral on both sides of the core, wherein the two skins (12, 16) include holes and wherein the holes of at least one of the two skins are micropores A method for producing this panel is also disclosed

Higher-Order Buckling of Debonded (Delaminated ) Sandwich Panels with Soft Core

Abstract: Buckling behavior of sandwich panels with a transversely e exible core that are debonded at one of their face sheet‐core interfaces is presented. The analytical model allows for a general cone guration of the sandwich panel and nonrigid bond layers between the face sheets and core. The governing equations with the associated boundary and continuity conditions are derived through the variational principle of virtual work. Buckling response of the panels with inner and edge debondings (delaminations ) is studied numerically. The effects of length and location of the delamination, face sheet rigidities, boundary conditions, and existence or inexistence of contact on the critical loads and buckling modes are presented. A comparison with experimental buckling modes is discussed, and conclusions are drawn.

Wet deck slamming experiments with a FRP sandwich panel using a network of 16 fibre optic Bragg grating strain sensors

Abstract: Drop test experiments have been performed with a FRP sandwich panel instrumented with a network of 16 fibre optic (FO) Bragg strain sensors, together with conventional electrical strain gauges for control and verification. The drop tests simulate slamming loads on the wet deck of a surface effect ship (SES). The objectives were to show the possibility of using a network of FO sensors to monitor strain during a slamming impact, and to test out a technique for signal processing. The strain measurements provided both peak strain data and served as a base for frequency analysis. The results showed that the FO strain sensors performed satisfactorily and were in general agreement with the conventional strain gauges used. The FO interrogation system was, however, not designed with sufficiently large dynamic range for the most extreme drop sequences. The peak strain in the panel was found to increase almost proportionally with the drop velocity, or drop height, and the wet fundamental frequency increased with increasing drop angle. Furthermore, the frequency decreased with increasing drop velocity.

No-septum acoustic sandwich panel, and apparatus and method for suppressing noise in a nozzle

Abstract: An acoustic panel comprises a core layer of honeycomb whose opposite sides are covered by face sheets each comprising a perforated metal plate and a sheet of metal cloth such as woven wire or metal felt. The perforated metal plates are bonded to the core and the metal cloth sheets form the outer surfaces of the panel. Each metal cloth sheet has an acoustic resistance of 5 to 300 Rayls. The perforated metal plates have an open area of about 20 to 40 percent in preferred embodiments. Noise in a nozzle is suppressed by disposing a plurality of the acoustic panels in the nozzle duct with the panels oriented radially and spaced apart about a circumference of the duct.

Behavior of Unidirectional Sandwich Panels with a Multi-Skin Construction or a Multi-Layered Core Layout-High-Order Approach

Abstract: The behavior of a unidirectional sandwich panel that consists of a multi-skin construction and a "soft" core is presented. In addition, a unidirectional sandwich panel with a core made of various layers, a multi-layered core, is discussed. The formulation is comprehensive, rigorous, and uses a variational approach that yields the field equations along with the appropriate boundary conditions for beams and unidirectional panels (wide beams). The governing equations for the two cases are presented for skins made of laminated composites with a general stacking sequence, and for a multi-layered core made of layers of isotropic or orthotropic materials. Typical panels that consist of a multi-skin construction are numerically studied. A unidirectional sandwich panel that has an edge with a cut-off is investigated and the involved stress concentration is examined as well. The effect of additional skin layers at mid height of the panel is presented and compared with an ordinary panel that consists of two skins. T...

Composite panel with fire resistant face sheets

Abstract: A fire resistant laminate for application to a core structure (12) to form a sandwich panel (10) having fire resistant face sheets (14 & 16). The laminate includes a fire protection (18) in which at least one layer of fibers (22) is embedded within a cured inorganic polymer matrix (24). The laminate further includes an adhesive layer (20) for bonding to the core structure.

Damage detection of satellite structures by optical fiber with small diameter

Abstract: Although there have been many researches concerning health monitoring system in the aerospace field, most of such researches relate to aircraft; there are only few that relate to satellite structures. This research first points out merit of the health monitoring system. The health monitoring system usually utilizes optical fiber sensor of which the diameter is 125 micrometer. However, such fiber sensors tend to be perceived as obstacles within the structure, which affects the soundness of the structure. This is especially the case in satellite structure, which utilizes especially thin composite laminates. In view of this problem, this study utilizes small diameter optical fiber, which is less likely to affect the soundness of the structure. The optical fiber is 40 micrometer in cladding diameter, and is embedded in the composite laminate structure. The structure and the optical fiber have been visually observed. Also, tensile test has been conducted on the structure. The result of the study indicates that the small diameter optical fiber can be embedded in the structure without affecting the soundness of the structure. The study further found that compressive destruction of a face sheet of a honeycomb sandwich panel having thin face sheets can be detected by utilizing this optical fiber.

Sandwich panel and method of manufacturing the sandwich panel

Abstract: A sandwich panel is manufactured by the following steps: a first step of attaching another end portion of an insert (1) whose one end portion is made sharp (1b, 1c, 1d) to the inner side of a facing member (2) in which a hole (6) has been cut in advance; a second step of pressing the insert (1) into the core member (4) such that the one end portion of the insert (1) force-cuts the core member (4); and a third step of attaching another facing member (2) to a side of the core member (4) opposite to the insert-inserting side thereof.

Sandwich panel, insert therefor, structure comprising sandwich panels and method of joining such panels

Abstract: A sandwich panel (1, 2) comprising a core material (3) sandwiched between plate members (4), and an insert member (9) locally replacing the core (3) and having a profile so as to intermesh with an appropriately profiled member on the unit to which it is to be connected. Further described is a method of connecting sandwich panels comprising a core material sandwiched between plate members, to a unit, comprising inserting an insert member having a profiled side so as to interlock with an appropriately profiled member on the unit to which it is to be connected.

Design Considerations for Buckling in ComDosite Wind Turbine Blades

Abstract: In this paper, design considerations, analysis techniques, and experimental ver&cation for bucklingcritical designs are provided. This presentation begins with a basic overview of the buckling prob lem, followed by design and analysis methodologies. Simple shell analyses are discussed, along with detailed, large deflection finite element post-buckling responses of typical wind turbine blade structures. An experimental verification program is reviewed with analytical/experimental correlations for stiffened, sandwich panel configurations. The basic results for this study are correlations for criticaland post-buckling structural responses for composite sub-structures that may be used in wind turbine blades. Good experimental/analytical correlations were found for this complicated, nonlinear problem. A methodology is provided for the design of composite wind turbine blades against buckling using finite element models.

Connecting/sealing extrusion for edge of sandwich panel used for wall facings or partitions has joint surface with tongue, groove and seals

Abstract: The extrusion (100) has a flat face (106) which is joined to the edge of a panel, upper and lower surfaces (108, 110) lying parallel to the panel's main faces, and a joint surface with a tongue (102), groove (104) and seals (118, 146) The joint surface is designed to engage with a matching and opposite surface on an adjacent panel, and the tongue is shaped to form a drainage channel (156)

Method for manufacturing a composite sandwich panel and panel obtained thereby

Abstract: A composite material has an open cellular core, whose cells are closed with foam. The faces of the core are covered with a barrier fabric and fibres impregnated in a polymerized resin that adheres to the core. An Independent claim is included for manufacturing a composite material as above includes assembling in a mould a cellular core covered in turn with a fireproof film, a dry barrier fabric, dry fibres. The mould is closed. Heat and pressure is applied to the assembly so the film polymerizes and expands to close off the cells without impregnating the barrier fabric. Resin is injected into the mould under vacuum to impregnate the barrier fabric and dry fibres. The resin is polymerized and the mould opened.

Acoustic sandwich panel with several degrees of freedom has two or more cellular layers of different dimensions with porous separators

Abstract: The sandwich panel, made from metals, thermoplastics or composition materials, has a resistive layer (14) forming its front face and a cellular structure (16) made from at least two cellular layers (18a, 18b, 18c) with porous separators (24) between, and a reflector (17) forming the rear face. The cellular structure is made from layers with cells of different dimensions, positioned alternately. The difference in the cellular networks of the layers is about 30 mm, and the structure has, for example, a layer with relatively large cells between two layers having smaller cells.

Plasma display device having reinforcement member

Abstract: In a plasma display device, a reinforcement member 15 constituted of a sandwich panel (laminated panel) formed by sandwiching a honeycomb core 151 made of aluminum alloy with aluminum alloy plates 153 is mounted on the back surface of a display module 10 . The reinforcement member 15 is light in weight, satisfies the abuse load requirements, and is equipped with supporting members 17 having cooling fins 171 mounted to the interior of said members 17 and providing heat diffusing function to the supporting members.

Sandwich panel for satellite structure

Abstract: PROBLEM TO BE SOLVED: To reduce the load imposed on equipment on board when a rocket is launched, by bonding a metal part embedded into a sandwich panel to the sandwich panel with a filler which has a vibration suppressing function. SOLUTION: A metal part 4 is inserted into a hole opened in a sandwich panel. A liquid filler 9 is injected through slots opened on the surface of the metal part 4, and the hole and gaps around a honeycomb core 2 are filled. After that, the filler is cured, and the honeycomb core 2 and a surface member are bonded to the metal part 4. For the surface member 1, a composite material whose reinforcements are aluminum and carbon fibers and whose matrix is an organic member is used, for example. For the honeycomb core 2, a composite material whose reinforcements are aluminum and aramid resins and whose matrix is an organic member is used, for example. For the filler 9, a polymer such as rubber or gel silicon is used. This makes it possible to reduce the load imposed on equipment on board, and limit the increase in the mass of the equipment on board when a rocket is launched.

Loading, Degradation and Repair of F-111 Bonded Honeycomb Sandwich Panels - Preliminary Study

Abstract: : Many of the fixed and removable panels on the RAAF F-111 aircraft are made up of bonded honeycomb sandwich panels. Experience with the RAAF fleet has shown that a serious problem exists with degradation and damage of these panels. A review of the literature was undertaken to gain an understanding of the extent of this problem. It was found that panels were subject to large areas of adhesive bond separation and corrosion damage. This damage was believed to be caused by the ingress of water in the panel through poor sealing at the edges or after repair of the panels. Moisture in the panel is also believed to cause adhesive degradation that may reduce the strength of the bonds in such panels. At the same time the literature was surveyed to determine the design load cases for such panels. This information was used to develop a simple finite element model of a bonded honeycomb sandwich panel. This model was in turn used to generate data on the loading and failure of such panels. In addition, an understanding ofF-111 Structural Repair Manuals and the RAAF Engineering Standard C5033.

Numerical approach to calculate thermal expansion of honeycomb sandwich panel with composite face sheets

Abstract: The aim of this paper is to show an accurate method to predict thermal deformations of honeycomb sandwich panels having composite skins First of all, some problems of the conventional method using the laminate theory are pointed out In order to develop an effective predicting method, a model on detailed structure of a unit cell for sandwich panels is developed utilizing the 3D finite element method A periodic boundary condition is introduced to the model to represent the repetitive structures of the sandwich panel The effective elastic modulus of the cell foil is obtained from the result of an out-of-plane compressive test on the honeycomb core The adhesives between skin and core is modeled by considering its shape and quantity The difference between the CTE according to this model and the actually measured one is approximately 01 × 10-6/K The paper further attempts to explain the anisotropic character of the sandwich panel The result of this analysis suggests that the direction-dependency of the