Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
  • B32B5/18—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by features of a layer of foamed material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
  • B32B5/22—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
  • B32B5/24—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being a fibrous or filamentary layer
  • B32B5/245—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being a fibrous or filamentary layer another layer next to it being a foam layer
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
  • B32B5/22—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
  • B32B5/32—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed at least two layers being foamed and next to each other
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
  • B63B5/00—Hulls characterised by their construction of non-metallic material
  • B63B5/24—Hulls characterised by their construction of non-metallic material made predominantly of plastics
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2266/00—Composition of foam
  • B32B2266/02—Organic
  • B32B2266/0214—Materials belonging to B32B27/00
  • B32B2266/0221—Vinyl resin
  • B32B2266/0228—Aromatic vinyl resin, e.g. styrenic (co)polymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2305/00—Condition, form or state of the layers or laminate
  • B32B2305/08—Reinforcements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2309/00—Parameters for the laminating or treatment process; Apparatus details
  • B32B2309/08—Dimensions, e.g. volume
  • B32B2309/10—Dimensions, e.g. volume linear, e.g. length, distance, width
  • B32B2309/105—Thickness
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24942—Structurally defined web or sheet [e.g., overall dimension, etc.] including components having same physical characteristic in differing degree
  • Y10T428/2495—Thickness [relative or absolute]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/249921—Web or sheet containing structurally defined element or component
  • Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/249921—Web or sheet containing structurally defined element or component
  • Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]
  • Y10T428/249981—Plural void-containing components

Definitions

• the invention relates to the field of sandwich-type laminated structures, that is to say structures comprising at least three layers of superimposed materials, one of the layers, called the core layer, comprising a cellular material (little or no compressible), and being bonded on each of its faces to a reinforcing material.
• These layers of material generally have a dimension (thickness) much smaller than their other dimensions, and the reinforcing layers generally have a thickness of at least 5 to 10 times less than the thickness of the core layer.
• the laminated sandwich structures are appreciated for the very good ratio that they display between their weight and their mechanical strength, in particular from the point of view of their stiffness in bending.
• the layers are bonded together, by any form of bonding, welding, etc., so that the bending of the structure results in a stressing of the (thin) reinforcing layers essentially in tension or in tension. compression, the core layer (thicker) being essentially stressed in compression in the direction of its thickness, and in shear in its general plane.
• light materials are generally used, most often cellular materials having a bulk density of less than 400 kg / m 3 and / or woody materials such as wood or other wood-based materials. . These materials are generally substantially rigid in compression in the direction of their thickness, at least in the field of efforts for which the structure is provided.
• the composite materials composed of fibers embedded in a plastic resin are appreciated for their mechanical characteristics and for their relative ease of use.
• other reinforcing materials are usable, such as metals (including aluminum), wood, or plastics with good mechanical properties.
• a sandwich laminate structure essentially comprises three interconnected layers, it may comprise complementary layers, either in the form of external layers superimposed on one or other of the reinforcing layers, or in the form of intermediate layers. arranged between a reinforcing layer and the core layer. In the latter case, it is important to maintain good adhesion between the different layers so that the shear forces can be transmitted from one layer to another.
• the invention may find application in many fields, including those of shipbuilding, aeronautics, rail or automobile. It may also apply to the field of sports gear such as gliding machines.
• the invention proposes a sandwich-type laminated structure comprising at least a first core layer made of cellular material, a first reinforcing layer bonded to a first face of the first core layer, and a second reinforcing layer on the side bonded to the second face of the core layer, characterized in that the laminated structure comprises at least, between the first core layer and the first reinforcing layer, a compressed foam layer bonded to these two layers.
• FIG. 1 is a schematic perspective exploded view of a sandwich structure sample according to a first embodiment of the invention
• Figure 2 is a sectional view of the sample of Figure 1
• Figure 3 is a view similar to that of Figure 1 illustrating a second embodiment of the invention
• Figure 4 is a view similar to that of Figure 1 illustrating a third embodiment of the invention.
• FIG. 1 illustrates in exploded perspective a first example of a sample of a sandwich structure 10 according to the invention.
• the notions of "superior”, “lower”, “high” and “low” will be used with reference to the appended drawings, and only in order to facilitate the understanding of the description, without being limiting in nature. the scope of the invention.
• This structure is here composed of layers in the form of plates, in that they have a dimension (their respective thicknesses) much lower than their two other respective dimensions. These plates are essentially flat, but they could be curved in two or three dimensions, developable in the mathematical sense or not.
• the sandwich structure 10 thus comprises a core layer 12 of cellular material on both sides of which are arranged reinforcing layers 14.
• the cellular material of the core layer 12 is chosen from foams, in particular from so-called rigid foams.
• Rigid foams have a low elasticity in that as soon as the compression force exceeds a certain value, they deform by collapse, irreversibly or very little reversible.
• Rigid foams include polyurethane foams, expanded polystyrene foam and extruded polystyrene foam which are generally used in the form of foam bars to form the cores of traditional surfboards.
• some foams of PVC or polyimide used generally as a core in the sandwich structure are part of so-called rigid foams.
• foams of expanded polyolefins are generally considered by those skilled in the art to be flexible foams, in particular by their capacity to be able to undergo large deformations in the elastic domain.
• the material of the core 12 is an extruded polystyrene foam such as that marketed by The Dow Chemical Company under the trademark “Styrofoam” and under the reference "HD300". This foam has a density of 45 kg / m3.
• any other cellular material may be considered, especially any cellular material of less than 150 kg / m 3, such as most plastic foams.
• the reinforcing layers 14 are advantageously layers of composite material such as fibers (glass, carbon, aramid, or mixtures thereof) impregnated or embedded in a resin (thermoplastic or thermosetting, for example of the polyester or epoxy type).
• the fibers will preferably be chosen from long woven fibers, with the possibility of superimposing several fabrics (identical or different, with different fiber orientations) within the same reinforcing layer 14.
• the sandwich structure 10 comprises, between the core layer 12 and at least one of the reinforcing layers 14 (in this case the upper reinforcing layer in the drawings), a layer of compressed foam 16 which is directly bonded or indirectly to these two layers 12, 14.
• the compression operation will generally be performed as an operation prior to assembling the composite structure.
• this compression operation will be a thermocompression operation, that is to say carried out in the presence of a heat input, to bring the material in a state favorable to its plastic deformation capacity.
• a compressed foam layer having a density of between 150 and 500. kg / m3.
• the thickness of the compressed foam layer will be between 0.3 and 2 mm.
• thermocompression is performed with a minimum heating time before the actual compression phase, so that the foam plate does not have time to see its temperature to homogenize in the thickness. Under the effect of pressure, the outermost parts of the plate will be more easily deformable than the heart and will be more compressed.
• thermoforming operation with plastic compression could also be performed directly at the output of the foam production line, for example by calendering directly at the extruder outlet for the case of an extruded foam.
• connection between the different layers of the sandwich structure (essential so that the shear stresses are transmitted from one layer to another and so that the structure can function as a sandwich structure and not as a simple stack), can be performed in different ways, according to the procedures known to those skilled in the art for making sandwich structures.
• the reinforcing layers will be bonded to the core layer or to the foam layer compressed by said resin.
• reinforcement layers made of other materials, they may be bonded to the adjacent layer by a suitable adhesive.
• This layer of fiber-reinforced adhesive then forms a layer of interlayered composite material 15 between the compressed foam layer 16 and the core layer 12, these two layers then being indirectly bonded to one another via the layer insert 15 which is related to both.
• This intermediate layer 15 can be made in the form of a reinforcing layer, for example combining fibers and resin, or in any other form of reinforcement layers as seen above. .
• the foam layer 16 thus compressed has the advantage of having a high resistance to any new compressive stress in a plane perpendicular to the structure.
• the core layer It thus protects the core layer from this type of stress which may appear for example when the sandwich structure is stressed in flexion.
• the reinforcing layer 14 arranged on the internal side of the flexion (that which sees its concavity increase) is stressed in compression in its plane and may therefore tend to flare inwards, towards the core layer 12.
• the reinforcing layer 14 is better held, and flambera for higher stress rates.
• the structure will be stronger when a point load is applied perpendicular to its reinforced surface.
• the compressed foam layer has a thickness at least four times less than the thickness of the core layer.
• the thickness ratio between the core layer and the compressed foam layer it will be advantageous for the thickness ratio between the core layer and the compressed foam layer to be even greater, for example at least 10.
• the compressed foam layer is compressed to have substantially smooth upper and lower faces.
• the sample differs from the first only in that, according to a second aspect of the invention, the compressed foam comprises, on one of its faces (in the occurrence on its upper face arranged on the side of the upper reinforcing layer 14), engravings 30.
• the etchings 30 are carried out without removal of material, by simple plastic compression of the light material. They can thus be made by supporting a tool (for example a plate or a roll provided with ribs) in a direction substantially perpendicular to the general plane of the light layer, the tool leaving the impression of its ribs after have plastically compressed the material.
• a tool for example a plate or a roll provided with ribs
• the etching can be performed before, during, or after the foam compression operation.
• the etchings are formed during this step, for example by interposing a flexible grid between the material and the mold or the press (flexible or rigid ) of thermoforming.
• the engravings 30 may have various geometries.
• the engravings may for example have a V shape, a shape with parallel flanks and rounded bottom, or have a flared shape.
• they may be for example in the form of furrows (straight lines, curves, segments, etc ). They can form an ordered network (parallel, crossed paths, arranged in a particular symmetry etc.) or a random network. They may eventually draw geometric figures, or even decorative patterns or text elements.
• the etchings 30 form two crossed gratings of parallel lines drawing cells in parallelograms (rhombs, rectangles, squares, etc.).
• the engravings may have a depth of about 0.1 mm to 0.5 mm or more for relatively thick layers of compressed foam.
• the depth of the etchings may be just less than the thickness of the compressed foam layer, for example of the order of 0.9 times the thickness. In the latter case, the engravings will make the compressed foam layer particularly flexible and able to conform to a complex three-dimensional form, even if it is not developable.
• the etchings 30 are intended to be filled by the resin which forms the matrix of the composite material of the adjacent layer.
• This adjacent layer is, in FIG. 4, the upper reinforcement layer 14.
• the layer of composite material 14 has, on its interface surface with the compressed foam layer 16, raised ribs whose shape is directly complementary to the shape of the etchings 30 of the compressed foam layer 16.
• the polymerization step of the resin which impregnates the fibers under pressure is carried out, for example by arranging the laminated structure in a flexible membrane enclosure, and establishing a pressure differential between the inside and the outside of the membrane. the enclosure so that the flexible membrane intimately presses the layer of fibers and resin during polymerization against the compressed foam layer 16.
• the pressure differential can be obtained by creating a depression inside the speaker, or creating an overpressure outside the enclosure. In this way, it ensures a good flow of the resin between the fibers and into the etchings 30, thus forming the ribs.
• the engravings are filled with resin, it is particularly important that the engravings are shallow and narrow.
• the network of resin ribs which is thus created at the interface between the compressed foam layer 16 and the composite reinforcing layer 14 has many advantages. Firstly, the presence of this network makes it possible to increase the contact area between the two layers, thus increasing the adhesion surface between the two layers, and therefore their cohesion, thus limiting the risk of delamination of the layers. This aspect is reinforced by the fact that the combination of ribs and complementary engravings performs a mechanical attachment by complementarity of shapes that completes the chemical bonding of the resin on the material of the compressed foam layer.
• the ribs make it possible to increase the mechanical performance of the structure, in particular because the composite layer is reinforced by the ribs and in particular is more resistant to flanking when the composite layer is stressed in compression in its general plane.
• the bending of the board is reflected, among other things, by a stress on the upper surface of the board in compression in its general plane.
• the reinforcement of the laminated structure according to the invention finds a particularly advantageous application for the realization of the upper faces of the board, as illustrated in the examples below.
• the network of engravings 30 and complementary ribs is a multidirectional and repetitive geometric pattern.
• the reinforcing effect acts substantially homogeneously in all directions.
• the reinforcement effect will also be more directional.
• the engravings are filled by a reinforcing reinforcement so that it is embedded in the compressed foam layer.
• the engravings it is possible for the engravings to be produced by pressing a grid (of metal, fibers, etc.) into the surface of the compressed layer, and to leave this grid in place in the compressed foam layer when the latter is compressed. is integrated into the sandwich structure to strengthen.
• sandwich structure according to the invention may comprise other additional elements, either at the core layer (reinforcing structures for example or multi-material cores), reinforcing layers (for example additional layers of protection or
• the layer of compressed foam has a substantially uniform density over its entire extent (if not over its entire thickness). that the density of the layer is not uniform but on the contrary the foam layer has denser areas than others, these denser areas being for example arranged in areas subject to higher stresses.
• the foam layer is made of several elements juxtaposed, each having undergone different compression rates, or being at constant compression ratio from foams of different initial densities. It is also possible to provide a one-piece multidensity layer. For this purpose, it is possible to form part of an initial foam layer having a uniform density but having a variable thickness. By subjecting it to a thermocompression operation during which the foam layer is brought to a substantially uniform thickness, the initially thicker areas will experience a higher compression ratio than the initially thinner areas, and will therefore be denser.
• the sandwich structure is reinforced only on one of these faces. This is particularly true for a structure that is asymmetrically solicited.
• the side of the structure which is most likely to undergo compressive forces perpendicular to the plane of the plates of the structure, and / or of the side of the structure for which the reinforcing layer is subjected to is preferably reinforced. compression in his plane.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• Ocean & Marine Engineering (AREA)
• Laminated Bodies (AREA)

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• 2005
  • 2005-10-24 FR FR0510810A patent/FR2892340B1/fr not_active Expired - Fee Related
• 2006
  • 2006-10-17 EP EP06820231A patent/EP1940619A1/de not_active Withdrawn
  • 2006-10-17 US US12/091,244 patent/US20080286543A1/en not_active Abandoned
  • 2006-10-17 WO PCT/FR2006/002337 patent/WO2007048899A1/fr active Application Filing

Non-Patent Citations (1)

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