Method of preparing composite material in sandwich form

Abstract

To provide a method of manufacturing a product in a sandwich form comprising a core and outer layers.SOLUTION: The outer layers may be composed of composite material comprising a fiber-reinforced polymeric matrix. The method uses an insert made of heat-resistant material, for example silicone. The object of this invention is to provide a method of manufacturing a sandwich that dissociates the choice of material of the core of the sandwich from the choice of the material of the outer layers.SELECTED DRAWING: None

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0001] The present invention relates to the field of composite products or composite materials. The products are resins made of polymeric materials, specifically thermoplastic or thermosetting materials. This means a product which may contain a fatty matrix. This matrix is ​​formed at a temperature below the melting point of the polymeric material. FRP is usually abbreviated as "fiber reinforced plastics". " refers to

[0002] FRP composite materials have good mechanical resistance relative to the weight of the material. FRP composites also have very good corrosion resistance. FRP type composite materials have properties superior to those of the parts they are made of. In the aircraft industry, it can reduce the weight of conventional steel parts. Also, FRP-type composite materials The material also has good fatigue resistance.

[0003] Composite reinforcement is achieved by the addition of mineral fibers dispersed within the matrix, either iron or synthetic. By using a support structure made of materials, by using reinforced fiber fabrics, nonwoven or by the use of mats, or other products obtained by weaving methods, can be obtained.

[0004] The fabric reinforcement may have a flat structure, with weft and warp threads interwoven perpendicularly. The manufacture of the fabric reinforcement requires the use of thread spools separate from the warp threads. could be.

[0005] In recent years, knitted reinforcements have been used. Knitted reinforcements are generally made by weaving yarns together to form a mesh. "means a product obtained from continuous yarns, arranged in successive rows, forming a sheave" The production of conventional knitted fabrics requires only a spool of yarn for the yarn mesh.

[0006] The yarn may be of the monofilament or multifilament type. The yarn is spun (i.e., made of parallel continuous filaments interwoven without twisting). yarns (i.e., a collection of short staple fibers twisted together); The yarn may also be a combination of several threads or filaments of different materials. The combination may be achieved by twisting or rolling. It is therefore possible to fabricate yarns that include polymeric materials and reinforcing materials. For example, aramid-type, carbon-type, and glass-type reinforcing yarns and thermoplastic yarns (i.e., polypropylene) are used. Can be combined with pyrene, polycarbonate, and polyetherimide (PEI) Such kind of yarn can be called blended yarn.

[0007] By knitting this kind of blended yarn, a preform containing both reinforcement and matrix can be produced. This preform is generally called "prepreg". In contrast to fabrics that are pre-impregnated with sticky, viscous resins, It is said that there is.

[0008] In addition, the two outer layers, or skins, are made of FRP-type composite materials, and the lightweight foam-type material The method is fabricated in the form of a sandwich, which may include a central body or core of a cellular honeycomb material. These products are sandwich-shaped structures, Much better performance can be achieved for the same weight.

[0009] The impregnation of the skin and the bonding of the skin to the core influence the final properties of the sandwich composite. Good impregnation of the husk generally requires a consolidation process with several stages, which can take some time. This is time and resource consuming, especially when the final product has a complex three-dimensional shape.

[0010] The traditional method of making a sandwich generally involves fabricating an outer layer using a pre-impregnated skin having a polymeric material; , juxtaposing outer layers on either side of a core, e.g., a honeycomb or foam; The outer layer is made of a special material to ensure the melting of the polymer material while ensuring the connection of all layers to the core. and b. consolidating the layer.

[0011] Depending on the thickness of the skin, several pleats may be required. Then, the fabric of each skin is To ensure good consolidation of the earth folds and to ensure good adhesion between the skin and the core, Several cures may be required. This method of manufacture requires that the outer layer is hardened to withstand the cure. The sandwich core can be specially selected for the desired temperature and pressure. It has also been shown that applying heat can damage the sandwich core. It has been observed that the foam core sags or shrinks during processing.

[0012] In addition, it appears that during curing, the polymeric material may flow into the honeycomb cells.

[0013] In the patent document EP0770472(A1), a core formed with an open-cell structure and fibers This paper outlines the manufacturing method for composite sandwich panels with a fiber and resin skin. In order to avoid melting of the resin in the open cells of the core, this patent document states that the skin and A watertight membrane and a thin film of adhesive are placed between the core and the mold. After closing the mold, one heat cycle is performed. The adhesive is polymerized in the cylinder, then the resin is injected into the fibers under pressure, and finally the resin is polymerized. This makes it possible to

[0014] However, this method requires the use of several layers, specifically a watertight membrane. This increases the cost of the final product.

[0015] In the patent document EP1086801(A1), a sandwich panel is made by resin injection technology RTM. This paper outlines a method for manufacturing a honeycomb panel. The method involves the use of a mold to avoid filling the honeycomb structure. Within the core, a thin film of intumescent material and a barrier fabric against each of the faces of the core must be placed.

[0016] In the method according to the invention, inserts of heat-resistant material are used instead of the core to form the outer layer. The insert is replaced by the core when the outer layer is consolidated. The wire is simply inserted to join the outer layer to the core.

[0017] According to a first embodiment, the method according to the invention comprises the steps of: For example, the outer layer may be formed by knitting or weaving threads that may include a polymeric material and a reinforcing material. Alternatively in the pre-impregnated skin embodiment, juxtaposing within a mold an outer layer, an insert of heat resistant material, and a second outer layer; It allows for the consolidation and fusion of polymeric materials without reaching the melting point of the reinforcing material. forming the skin by curing at a suitable temperature and pressure; The insert is removed and a layer of, for example, foam or Introducing a honeycomb sandwich core; The combination is cured at a temperature that allows for adhesion between the outer layer and the core of the sandwich. and

[0018] According to another embodiment, the skin is made of a woven reinforcement material, and the polymeric material is The present invention may be provided by

[0019] Then, the method comprises: A step in which a reinforcing fabric, an insert of heat-resistant material, and another reinforcing fabric are juxtaposed in the mold. P and Injecting resin; The insert is removed and a layer of, for example, foam or Introducing a honeycomb sandwich core; Curing the whole at a temperature that allows adhesion between the outer layer and the core of the sandwich. and

[0020] The insert may be rigid or non-rigid. In particular, it may be silicone. .

[0021] In some embodiments, the temperature may expand, thereby increasing the compression during consolidation. It is possible.

[0022] The inserts can provide a specific shape, e.g. a chamfer, to the final product. do.

[0023] In some embodiments, an adhesive layer may be interposed between the sandwich body and the outer layer. The adhesive may be a liquid adhesive, an adhesive film, or a woven preform containing thermoplastic fibers. This is also fine.

[0024] The outer layers may be the same or different.

[0025] Advantageously, in order to obtain a good sandwich effect, the thickness of the core is generally at least About 2 mm to about 50 mm or less, preferably at least about 3 mm to about 40 mm or less, more preferably or at least about 5 mm to about 25 mm, and the thickness of the outer skin is at least At most about 0.2 mm to about 5 mm, preferably at least about 0.4 mm to about 2 mm, more preferably More preferably, the thickness can be set to at least about 0.5 mm to about 1 mm.

[0026] The object of the present invention is to provide an alternative method for producing sandwiches, in particular To provide a manufacturing method that separates the selection of the material for the German body from the selection of the material for the outer layer. It can be said that:

[0027] Examples of polymeric materials include polycarbonate (PC), polyetherimide (PE I), polypropylene (PP), poly(ethylene terephthalate) (PET), Thermoplastic materials such as polyether ether ketone (PEEK) or other materials such as epoxy, cyanine, Examples of suitable materials include thermosetting materials such as esters, phenolics, polyesters, and the like.

[0028] Reinforcing materials include synthetic materials such as para-aramid and polypropylene, and natural materials such as linen. Materials may include inorganic materials such as glass, quartz, carbon, basalt, metals, and the like.

[0029] The method according to the invention separates the choice of the type of sandwich core from the choice of the deformation method. The method according to the invention has proven to be particularly advantageous since it makes it possible to This makes it possible to achieve good impregnation of the resin.

[0030] Many different aspects and embodiments are possible. After reading this specification, those skilled in the art will be able to easily understand these aspects and implementations. It will be understood that the embodiments are illustrative only and do not limit the scope of the present invention. Any one or more of the embodiments listed below may be followed.

[0031] Embodiment 1. A method for producing a sandwich-type composite product, comprising: The composite product has two outer layers and a core. The outer layers are made of a matrix of fiber-reinforced polymer material. the polymeric material has a melting point lower than the melting point of the material constituting the fiber; An insert made of a material having a melting point higher than that of the polymer material is used, The outer layer is then compacted onto the insert, which is then replaced by the core of the sandwich. The assembly is then subjected to a consolidation process to bond the outer layer to the core. How to do it.

[0032] Embodiment 2. From a fiber-reinforced polymeric material intended to be the outer layer of the sandwich The method includes the steps of: preparing a preform; placing a first preform, an insert, and a mold; and placing the first preform and the second preform side by side; and Heat and pressure are applied so as to reach the melting point of the polymeric material without reaching the melting point of the and debulking the preform to obtain an outer layer by removing the insert. separating the outer layer and inserting a sandwich core; and bonding the outer layer to the core. and cooling the product thus obtained. 2. The method of embodiment 1, characterized in that

[0033] Example 3. A preform is made using a pre-impregnated polymeric resin fabric. 3. The method of embodiment 2, wherein

[0034] Embodiment 4. The preform is produced by weaving a yarn containing a reinforcing material and a polymeric material. 3. The method of embodiment 2, wherein the

[0035] Embodiment 5. A preform where it is intended to form a coreless zone. 3. The method of embodiment 2, further comprising adding a peeling cost in between.

[0036] Embodiment 6. In the mold, a fabric or knit made of a reinforcing material, an insert, and a reinforcing A step of juxtaposing a second fabric or knit made of the material and compressing the resin of the polymer material. and removing the insert to remove the sandwich core. and a consolidation and curing step for bonding the outer layer to the sandwich core. and cooling the product thus obtained. The method according to aspect 1.

[0037] Embodiment 7. The method according to embodiment 1, wherein the insert is made of silicone. How to.

[0038] Embodiment 8. The reinforcing material is selected from glass fiber, carbon fiber, and aramid fiber. 2. The method of embodiment 1,

[0039] Embodiment 9. The polymeric material is a thermoplastic type material, specifically polycarbonate. (PC), polyetherimide (PEI), polypropylene (PP), poly(ethylene terephthalate) Polyether ether ketone (PEEK) 2. The method of embodiment 1, wherein

[0040] Embodiment 10. The polymeric material is a thermosetting type material, specifically, epoxy, shear. esters, phenolic resins, and polyesters. 2. The method according to embodiment 1.

[0041] Embodiment 11. The sandwich core is preferably constructed from a cellular honeycomb material. 2. The method of embodiment 1, wherein the

[0042] Embodiment 12. The thickness of the core is at least about 2 mm to about 50 mm. 2. The method of embodiment 1, wherein

[0043] Embodiment 13. The thickness of each of the outer layers is at least about 0.2 mm to about 5 mm. 2. The method of embodiment 1, wherein

[0044] The following examples illustrate the invention in a non-limiting manner. EXAMPLES

[0045] Example 1 Several carbon fiber cloths impregnated with cyanate esters, called "prepregs," are used. The ground is draped onto a steel mould to form the first skin of the sandwich.

[0046] A rigid insert (e.g. a block of Teflon (registered trademark) of several millimeters) is deposited on the fabric. Can.

[0047] The second skin of the sandwich is made of some "prepreg" fabric draped over a rigid insert. It is made by rapping.

[0048] Teflon-coated release layer (PTFE-coated fiberglass) at the joint between the two skins The splice is where the skin joins and covers the area of ​​the core.

[0049] The type is closed by the flexible counter type.

[0050] The rind is consolidated by heat treatment under vacuum at about 180-220°C for several hours.

[0051] The assembly is cooled and the insert is removed.

[0052] A high temperature resistant adhesive is applied to each of the surfaces intended to be in contact with the core.

[0053] A polyimide foam core (approximate density 50 kg / m3) is introduced in place of the insert.

[0054] The entire sandwich is then vacuum sealed to ensure good adhesion between the skin and the core. The final compaction process is carried out at a temperature of about 90 to 120°C.

[0055] Example 2 The first skin is formed by laminating several layers of non-impregnated reinforcing fabric of carbon fiber deposited on a steel mould. will be done.

[0056] A soft insert (a silicone plate a few millimeters thick) is vapor-deposited onto the fabric.

[0057] The second skin is formed by the same type of fabric deposited on the insert.

[0058] The mould is closed by a steel counter mould. Cyanate ester resins can be decomposed by known RTM-type methods at pressures of 10-15 bar. It is poured at a temperature of 80 to 120°C.

[0059] The heat treatment lasts for 4 hours.

[0060] The mold is cooled, then the insert is removed and the skin is removed by removing the release layer. are separated.

[0061] A very thin layer of cyanate ester resin (intended to be in contact with the honeycomb) It is applied to the outer skin (on the surface).

[0062] Honeycomb cores are placed between two skins instead of inserts to form a sandwich. will be introduced. The entire sandwich is heat treated under vacuum for 4 hours (180°C) to bond the skin and core. ~200℃) is applied.

[0063] Example 3 The knitted fabric is made using a blended yarn containing glass and thermoplastic fibers.

[0064] The braid is deposited onto a steel mold to form the first skin.

[0065] Under the influence of temperature, an insert of expandable material is deposited onto the knitted fabric.

[0066] A second braid of the same type is deposited onto the insert to form a second skin.

[0067] Teflon-coated release layer (PTFE-coated fiberglass) at the joint between the two skins The splice is where the two skins join together to cover the core area.

[0068] A Teflon-coated release layer is placed at the joint between the two skins. The mould is closed by a steel counter mould.

[0069] The outer skin is heat treated at 200-250°C for several tens of minutes under a pressure of 3-10 bar. The mixture is compressed and consolidated.

[0070] The mold is cooled, then the insert is removed and the skin is removed by removing the release layer. are separated.

[0071] A woven preform of thermoplastic yarns forms a connecting layer between the core and the skin of the sandwich. To achieve this, the honeycomb core is deposited on both sides.

[0072] The honeycomb core and the woven fabric preform are then inserted into the insert to form a sandwich. Instead, it is introduced between the two skins.

[0073] The entire sandwich is heat treated under vacuum for several hours (20 0~250℃) is applied.

[0074] Example 4 The knitted fabric is made using a blended yarn containing glass and thermoplastic fibers.

[0075] The braid is deposited onto a steel mold to form the first skin.

[0076] A rigid insert of material expandable under the influence of temperature is deposited onto the knit.

[0077] A second braid of the same type is deposited onto the insert to form a second skin.

[0078] A Teflon-coated release layer is placed at the joint between the two skins.

[0079] The mould is closed by a steel counter mould.

[0080] The outer skin is heat treated at 200-250°C for several tens of minutes under a pressure of 3-10 bar. The mixture is compressed and consolidated.

[0081] The mold is cooled, then the insert is removed and the skin is removed by removing the release layer. are separated. Expanded epoxy foam core is used in place of the insert to form a sandwich with two pieces It is injected between the cuticles.

[0082] The entire sandwich is then heat treated for several hours under vacuum (65°C) to bond the skin and core together. ~120℃) is applied.

[0083] Example 5 The knitted fabric is made using a blended yarn containing glass and thermoplastic fibers.

[0084] A first fabric is draped over a silicone bladder and the combination is placed in a first steel mold. The skin is compacted by evaporation. The mould is closed and a vacuum is drawn. The mould is pressurised (3-10 bar). Then, the material is rapidly heated to a temperature of 200-250°C by induction heating. This temperature is maintained for several minutes. After cooling, the bladder is removed and the first skin is fabricated.

[0085] A second skin (inner skin) is made in the same manner as the first skin on a second mold.

[0086] The tool used to compact the skin must not be used to apply the previously compacted skin, epoxy or Successive deposition of liquid adhesive film, honeycomb structure and consolidated inner skin before the final composite material will be done.

[0087] The silicone bladder, which is used to compact the endothelium, is put in place and the mold is closed. To maximize the vacuum and bond the skin and core, the assembly is heated to 65-120°C. Heat to temperature for several hours (oven heating method).

Claims

1. A method for producing a sandwich composite product, comprising the steps of: The material product comprises two outer layers and a core, the outer layers being made of a matrix of fiber-reinforced polymeric material. the polymeric material has a melting point lower than the melting point of the material constituting the fiber, The method further comprises the step of: providing a polymeric material having a melting point greater than the melting point of the polymeric material; an insert is used, on which the outer layer is consolidated; The insert is then replaced into the core of the sandwich and then assembled. The assembly is characterized in that it is subjected to a consolidation process to bond the outer layer to the core. ,method.

2. Consists of a fiber-reinforced polymeric material intended to be the outer layer of the sandwich. producing a preform to be molded; A first preform, the insert, and a second preform are juxtaposed in a mold. Steps and without reaching the melting point of the reinforcement material or the material of the insert. The outer layer is heated and pressurized to reach the melting point of the polymeric material. consolidating the preform to obtain Remove the insert, separate the outer layers and insert the core of the sandwich. and heat treating the outer layer to bond it to the core; and cooling the product thus obtained. The method according to

3. The preform is made using a pre-impregnated polymeric resin fabric. The method according to claim 2 .

4. The preform is formed by weaving a yarn including the reinforcing material and the polymeric material.

3. The method of claim 2, wherein the

5. Delamination between the preforms at locations intended to form coreless zones.

3. The method of claim 2, further comprising adding a cost.

6. In the mold, a fabric or knit made of a reinforcing material, the insert, and a juxtaposing the produced second fabric or knit; injecting a polymeric resin under pressure and temperature; removing the insert and inserting the core of the sandwich; consolidating and curing the outer layer to adhere it to the core of the sandwich; 、 and cooling the product thus obtained. The method described above.

7. The method of claim 1 , wherein the insert is made of silicone.

8. It is preferred that the reinforcing material is selected from glass fibers, carbon fibers, and aramid fibers. The method of claim 1 ,

9. The polymer material is a thermoplastic material, specifically, polycarbonate (PC). , polyetherimide (PEI), polypropylene (PP), poly(ethylene terephthalate) Polyetheretherketone (PET), polyetheretherketone (PEEK), The method of claim 1 ,

10. The polymer material is a thermosetting material, specifically, epoxy, cyanate ester, etc.

2. The method according to claim 1, characterized in that the resin is selected from the group consisting of ethers, phenolic resins and polyesters. The method described above.

11. The sandwich core is constructed from a cellular honeycomb material. The method of claim 1 .

12. The thickness of the core is at least about 2 mm to about 50 mm. The method according to claim 1.

13. Each of the outer layers has a thickness of at least about 0.2 mm to about 5 mm. The method of claim 1 .