CN117359969A - Foam sandwich composite material structure and forming method thereof - Google Patents
Foam sandwich composite material structure and forming method thereof Download PDFInfo
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- CN117359969A CN117359969A CN202311418941.2A CN202311418941A CN117359969A CN 117359969 A CN117359969 A CN 117359969A CN 202311418941 A CN202311418941 A CN 202311418941A CN 117359969 A CN117359969 A CN 117359969A
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- foam
- composite material
- sandwich
- foam sandwich
- flat plate
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- 239000006260 foam Substances 0.000 title claims abstract description 336
- 239000002131 composite material Substances 0.000 title claims abstract description 132
- 238000000034 method Methods 0.000 title claims abstract description 63
- 238000000465 moulding Methods 0.000 claims abstract description 34
- 238000005253 cladding Methods 0.000 claims abstract description 23
- 239000002313 adhesive film Substances 0.000 claims abstract description 20
- 238000005520 cutting process Methods 0.000 claims abstract description 18
- 239000007787 solid Substances 0.000 claims abstract description 18
- 239000011248 coating agent Substances 0.000 claims abstract description 6
- 238000000576 coating method Methods 0.000 claims abstract description 6
- 239000003822 epoxy resin Substances 0.000 claims description 19
- 229920000647 polyepoxide Polymers 0.000 claims description 19
- 230000008569 process Effects 0.000 claims description 18
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 14
- 239000004917 carbon fiber Substances 0.000 claims description 14
- 238000005056 compaction Methods 0.000 claims description 11
- 229920005989 resin Polymers 0.000 claims description 10
- 239000011347 resin Substances 0.000 claims description 10
- 230000009471 action Effects 0.000 claims description 6
- 229920007790 polymethacrylimide foam Polymers 0.000 claims description 5
- 229920005830 Polyurethane Foam Polymers 0.000 claims description 4
- 238000013459 approach Methods 0.000 claims description 4
- 239000004744 fabric Substances 0.000 claims description 4
- 239000011496 polyurethane foam Substances 0.000 claims description 4
- XQUPVDVFXZDTLT-UHFFFAOYSA-N 1-[4-[[4-(2,5-dioxopyrrol-1-yl)phenyl]methyl]phenyl]pyrrole-2,5-dione Chemical compound O=C1C=CC(=O)N1C(C=C1)=CC=C1CC1=CC=C(N2C(C=CC2=O)=O)C=C1 XQUPVDVFXZDTLT-UHFFFAOYSA-N 0.000 claims description 3
- 229920003192 poly(bis maleimide) Polymers 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 8
- 238000010276 construction Methods 0.000 abstract description 4
- 239000011162 core material Substances 0.000 description 20
- 238000013003 hot bending Methods 0.000 description 7
- 238000012545 processing Methods 0.000 description 7
- 239000000463 material Substances 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 5
- 238000009826 distribution Methods 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 238000007493 shaping process Methods 0.000 description 4
- 230000007704 transition Effects 0.000 description 4
- 239000004593 Epoxy Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 229920006332 epoxy adhesive Polymers 0.000 description 3
- 238000003754 machining Methods 0.000 description 3
- 238000005452 bending Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000000748 compression moulding Methods 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000007731 hot pressing Methods 0.000 description 2
- 238000011031 large-scale manufacturing process Methods 0.000 description 2
- 239000013518 molded foam Substances 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 239000013585 weight reducing agent Substances 0.000 description 2
- 241000276425 Xiphophorus maculatus Species 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000009501 film coating Methods 0.000 description 1
- 239000006261 foam material Substances 0.000 description 1
- 238000010097 foam moulding Methods 0.000 description 1
- 239000003292 glue Substances 0.000 description 1
- 210000001503 joint Anatomy 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
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- 239000012783 reinforcing fiber Substances 0.000 description 1
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- 238000003892 spreading Methods 0.000 description 1
- 230000007480 spreading Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
- B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
- B29C70/28—Shaping operations therefor
- B29C70/30—Shaping by lay-up, i.e. applying fibres, tape or broadsheet on a mould, former or core; Shaping by spray-up, i.e. spraying of fibres on a mould, former or core
- B29C70/34—Shaping by lay-up, i.e. applying fibres, tape or broadsheet on a mould, former or core; Shaping by spray-up, i.e. spraying of fibres on a mould, former or core and shaping or impregnating by compression, i.e. combined with compressing after the lay-up operation
- B29C70/342—Shaping by lay-up, i.e. applying fibres, tape or broadsheet on a mould, former or core; Shaping by spray-up, i.e. spraying of fibres on a mould, former or core and shaping or impregnating by compression, i.e. combined with compressing after the lay-up operation using isostatic pressure
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B11/00—Making preforms
- B29B11/06—Making preforms by moulding the material
- B29B11/12—Compression moulding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
- B29C33/3842—Manufacturing moulds, e.g. shaping the mould surface by machining
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
- B29C33/40—Plastics, e.g. foam or rubber
Abstract
The invention relates to a foam sandwich composite material structure and a forming method thereof. The method comprises the following steps: parting the structure to be molded into a composite material solid part and a foam sandwich part, decomposing the foam sandwich part into a plurality of foam thin plates which are spliced, cutting the foam thin plates into a plurality of flat-plate-shaped foam thin plates, and coating the foam thin plates with an adhesive film to obtain coated foam thin plates; cutting out prepregs for the inner and outer bearing skins and preparing a mold for molding; laying up a prepreg for the outer load-bearing skin in a molding die and precompacting; laying a cladding foam sheet at the position of the foam sandwich part and pre-compacting; and (3) paving a prepreg for the inner bearing skin, and then performing curing molding and demolding to obtain the foam sandwich composite material structure. The invention provides a low-cost and high-efficiency forming method, which solves the problems of high manufacturing cost and long construction period of a foam sandwich composite material structure in the prior art and effectively improves production efficiency.
Description
Technical Field
The invention belongs to the technical field of composite structural member forming, and particularly relates to a foam sandwich composite structure and a forming method thereof.
Background
At present, the requirements of composite structural members on weight indexes are more strict, and weight reduction requirements are generally existed. On the premise of ensuring the strength, the foam sandwich structure can achieve a good weight reduction effect, so that the foam sandwich structure is widely applied. The foam sandwich composite material structure is prepared by machining foam plates according to the product modeling requirement, and then co-curing or bonding the foam plates with the composite material to obtain the required product. The foam structure used is determined according to the product modeling, and the foam machining process is complex, the period is long and the cost is high, so that the manufacturing cost and the production efficiency of the composite material are seriously affected; for example, in chinese patent application CN110481059a, in order to obtain a foam sandwich structure of a composite material with a large thickness and good skin molding quality, in the foam sandwich structure, although a method of splitting and splicing foam blocks is adopted, a foam core material needs to be machined first to match with a product structure.
Chinese patent application CN114986935a discloses a method for forming a resin-based radome with a core preform, in which the foam core is formed by hot-press forming (hot bending) the foam unit to form a foam unit in a shape conforming to a mold. However, foam materials are generally hard materials, direct hot press molding is difficult, and hot press molding is only suitable for construction molding with small radians and small dimensions.
In summary, it is highly desirable to provide a foam sandwich composite structure and method of forming the same.
Disclosure of Invention
In order to solve one or more technical problems in the prior art, the invention provides a foam sandwich composite material structure and a forming method thereof. The forming method of the foam sandwich composite material structure is a low-cost and high-efficiency forming process technology, solves the problems of high manufacturing cost and long construction period of the foam sandwich composite material structure in the prior art, effectively improves the production efficiency, and is generally applicable to various composite material structural members formed by autoclave, compression molding and expansion mold processes.
The present invention provides in a first aspect a method of forming a foam sandwich composite material structure, the method comprising the steps of:
(1) Dividing a foam sandwich composite material structure to be formed into a composite material solid part and a foam sandwich part, decomposing the foam sandwich part into a plurality of foam thin plates which are spliced, cutting the foam thin plates into a plurality of foam thin plates, and coating the foam thin plates with an adhesive film to obtain coated foam thin plates; the foam sheet and the coated foam sheet are flat;
(2) Cutting out prepreg for the outer bearing skin according to the structural shape of the foam sandwich composite material to be formed, prepreg for the inner bearing skin, and preparing a forming die according to the structural shape of the foam sandwich composite material to be formed;
(3) Paving a prepreg for the outer bearing skin in a molding die and pre-compacting to obtain an outer bearing skin prefabricated member;
(4) Laying a cladding foam sheet at the position of a foam sandwich part and pre-compacting to obtain a sandwich structure prefabricated member on the upper surface of the outer bearing skin prefabricated member;
(5) And (3) paving prepreg for the inner bearing skin on the upper surface of the prefabricated member of the sandwich structure, and then performing curing molding and demolding to obtain the foam sandwich composite material structure.
Preferably, in step (1), when the foam sandwich portion includes a non-flat plate structure, a cutting process is required to be performed on a position of the non-flat plate structure, and cutting is performed on a position with smaller corners or a part of the non-flat plate structure in an arc shape, so as to cut a plurality of approximate flat plate areas; in step (4), laying at least one coated foam sheet layer by layer in the thickness direction of each approximate flat area until reaching the preset approximate flat area thickness; in step (4), composite ribs are provided between the slit approximately flat areas.
Preferably, when a plurality of coated foam sheets are laid layer by layer in each approximately flat area, the thickness of the coated foam sheets is not more than 5mm, preferably 2 to 4mm.
Preferably, when the foam sandwich composite material structure is large in size, the foam sandwich part is formed by splicing a plurality of coated foam blocks in the plane direction and/or the curved surface direction.
Preferably, the prepreg is made of carbon fibers impregnated with epoxy resin, wherein the carbon fibers are unidirectional carbon fibers of grade T300, grade T700, grade T800, grade T1000, grade M40J or grade M55J, and the epoxy resin is medium-temperature cured epoxy resin, high-temperature cured epoxy resin or bismaleimide resin; and/or the foam adopted by the foam sandwich part is PMI foam or polyurethane foam.
Preferably, the precompaction is: sequentially laying release cloth and airfelt on the surface of a member to be pre-compacted, then placing the member into a vacuum bag, and pre-compacting the member by a vacuum bag method, wherein the pre-compacting temperature is 40-50 ℃ and the pre-compacting time is 20-40 min; and/or in the step (5), curing and forming by an autoclave, wherein the curing and forming temperature is 120-130 ℃, the curing and forming pressure is 0.4-0.6 MPa, and the curing and forming time is 2-4 h.
Preferably, during the precompaction process, the flat-plate-shaped cladding foam sheet laid in the approximate flat-plate area is made to approach to follow the die under the action of vacuum pressure; in the solidifying and forming process, the cladding foam sheet is adhered to the inner and outer bearing skins by using the pressure of an autoclave, and meanwhile, the flat cladding foam sheet approaching to the following mold is adhered to the following mold surface.
Preferably, the foam sandwich composite material structure is a foam sandwich composite material flap structure, and the foam sandwich part of the foam sandwich composite material flap structure comprises a foam sandwich flat plate part and foam sandwich arc plate parts positioned at two sides of the foam sandwich flat plate part, and the foam sandwich flat plate part is in smooth transition connection with the foam sandwich arc plate parts.
Preferably, a plurality of approximate flat plate areas are cut on the foam sandwich arc plate part, and composite material ribs are arranged between the approximate flat plate areas and/or between the approximate flat plate areas and the foam sandwich flat plate part; the foam sandwich flat plate part is paved with a coated foam sheet with the thickness of 5-10 mm; and/or laying a plurality of coated foam thin plates with the thickness of 2-4 mm layer by layer in the approximate flat area until the thickness of the preset approximate flat area is reached.
The present invention provides in a second aspect a foam sandwich composite structure formed by the forming method of the invention described in the first aspect.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) The invention provides a low-cost and high-efficiency forming method of a foam sandwich composite material structure, which adopts a splicing scheme of foam thin plates (thin flat plates) according to the foam structure and the distribution form in a product, namely, the foam is divided into thin plates with different sizes and thicknesses according to the characteristics of a foam distribution area, and the thin plates are embedded layer by layer according to the characteristics of the product to form a designated structure without complex machine heating or hot bending treatment; the foam used in the invention only needs to be mechanically processed into foam flat plates with different thicknesses in the thickness direction and/or into foam flat plates with different sizes in the length-width direction, three-dimensional complex modeling processing is not needed, the thin flat plates are directly embedded layer by layer according to the regional characteristics, and the foam flat plates and the mould can be subjected to hot pressing by utilizing the pressure applied in the pre-compaction and curing processes, so that the product modeling is obtained.
(2) Experiments prove that the performance effect of the product obtained by the forming method of the foam sandwich composite material structure provided by the invention is equivalent to that obtained by the forming method of foam mechanical processing or foam hot bending treatment, but the manufacturing cost can be saved by 60-70%, and the mechanical processing period or hot bending period can be effectively shortened; the foam sheet raw material can be used for modeling various products, has no limitation on the size and curvature of the products, is also suitable for shaping a composite material structure with large size, large curvature and large radian, can effectively avoid the uniqueness of the corresponding products after the foam machine is processed, can effectively avoid the complexity of heat bending treatment on the operation of the large-size, large curvature and large radian components, and provides a low-cost and high-efficiency shaping process technology for large-scale production.
Drawings
The drawings of the present invention are provided for illustrative purposes only and the proportion and the size of the parts in the drawings do not necessarily coincide with the actual products.
FIG. 1 is a product schematic illustration of a formed foam sandwich composite material flap construction in accordance with some embodiments of the invention;
FIG. 2 is a schematic cross-sectional view of the foam sandwich composite material flap structure of FIG. 1 prior to parting;
FIG. 3 is a schematic cross-sectional view of the foam sandwich composite material flap structure of FIG. 1 after parting and slitting in accordance with the molding method of the present invention;
in the figure: 1: a load-bearing skin; 2: a foam sandwich portion; 21: a foam sandwich panel portion; 22: a foam sandwich arcuate plate portion; 221: an approximate flat plate area; 3: a composite solid portion; 4: composite ribs.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below in connection with the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The present invention provides in a first aspect a method of forming a foam sandwich composite material structure, the method comprising the steps of:
(1) Dividing a foam sandwich composite material structure to be formed into a composite material solid part and a foam sandwich part, decomposing the foam sandwich part into a plurality of (a plurality of) foam thin plates, splicing the foam thin plates, cutting the foam thin plates into a plurality of foam thin plates, and coating the foam thin plates with an adhesive film to obtain coated foam thin plates; in the invention, a foam sandwich composite material structure to be formed comprises a sandwich structure which is divided into a composite material solid part and a foam sandwich part, wherein the composite material solid part is used for covering the foam sandwich part; in the present invention, the "composite solid portion" is entirely composed of the composite material; the foam sheet and the coated foam sheet are flat; in the present invention, the thickness of the adhesive film covering the foam sheet may be, for example, 0.1 to 0.2mm; in the present invention, "plurality" means two or more; under the condition that no special description exists, the surface of the foam sheet is fully coated (fully coated) by the adhesive film to obtain the coated foam sheet;
(2) Cutting out prepreg for the outer bearing skin according to the structural shape of the foam sandwich composite material to be formed, prepreg for the inner bearing skin, and preparing a forming die according to the structural shape of the foam sandwich composite material to be formed; preferably, the prepreg for the solid part of the composite material is cut out according to the structural shape of the foam sandwich composite material to be molded, and the prepreg for the solid part of the composite material, the prepreg for the outer bearing skin and the prepreg for the inner bearing skin are all made of the same material;
(3) Paving a prepreg for the outer bearing skin in a molding die and pre-compacting to obtain an outer bearing skin prefabricated member;
(4) Laying a cladding foam sheet at the position of a foam sandwich part and pre-compacting to obtain a sandwich structure prefabricated member on the upper surface of the outer bearing skin prefabricated member; laying a cladding foam sheet at the position of a foam sandwich part, laying prepreg for a composite material solid part at the composite material solid part, and then pre-compacting to obtain a sandwich structure prefabricated part on the upper surface of the outer bearing skin prefabricated part;
(5) Spreading prepreg for inner bearing skin on the upper surface of the prefabricated member of the sandwich structure, and then carrying out curing molding and demolding to obtain a foam sandwich composite material structure; in the curing and forming process, the platy cladding foam sheet and the mold surface follow-up under the action of pressure, and the bonding surface of the cladding foam sheet and the composite material can be bonded through the cladding adhesive film, so that the bonding quality is ensured, and the integrally formed foam sandwich composite material structure is obtained; in the invention, the prepreg of the inner bearing skin can be directly cured and molded after being paved, the pre-compaction can be carried out only after the prepreg of the outer bearing skin and the coated foam sheet are paved, whether the pre-compaction is carried out after the prepreg for the inner bearing skin is paved or not can be regulated according to the thickness of the skin, the thickness of the foam, the structural characteristics and the like.
The invention provides a low-cost and high-efficiency forming method of a foam sandwich composite material structure, which adopts a splicing scheme of flat foam sheets (thin plates) according to the foam structure and the distribution form in a product, namely, the foam is divided into sheets with different sizes and thicknesses according to the characteristics of a foam distribution area, and the sheets are embedded layer by layer according to the characteristics of the product to form a designated structure without complex machine heating or hot bending treatment of the foam; the foam used in the invention only needs to be mechanically processed into foam flat plates with different thicknesses in the thickness direction and/or into foam flat plates with different sizes in the length-width direction, three-dimensional complex modeling processing is not needed, the thin flat plates are directly embedded layer by layer according to the regional characteristics, and the foam flat plates and the mould can be subjected to hot pressing by utilizing the pressure applied in the pre-compaction and curing processes, so that the product modeling is obtained.
Experiments prove that the performance effect of the product obtained by the forming method of the foam sandwich composite material structure provided by the invention is equivalent to that obtained by the forming method of foam mechanical processing or foam hot bending treatment, but the manufacturing cost can be saved by 60-70%, and the mechanical processing period or hot bending period can be effectively shortened; the foam sheet raw material can be used for modeling various products, has no limitation on the size and curvature of the products, is also suitable for shaping a composite material structure with large size, large curvature and large radian, can effectively avoid the uniqueness of the corresponding products after the foam machine is processed, can effectively avoid the complexity of heat bending treatment on the operation of the large-size, large curvature and large radian components, and provides a low-cost and high-efficiency shaping process technology for large-scale production.
According to some preferred embodiments, in step (1), when the foam core portion includes a non-flat plate structure, a slitting process is required for the position of the non-flat plate structure, and a plurality of approximate flat plate regions are slit at positions with smaller corners or partial arc shapes; in the present invention, it is preferable that the foam sandwich portion includes a non-flat plate structure and a flat plate structure; in step (4), laying at least one coated foam sheet layer by layer in the thickness direction of each approximate flat area until reaching the preset approximate flat area thickness; in particular, in the present invention, when two or more foam sheets are to be laid layer by layer in the thickness direction of each approximately flat plate region, two or more fully-wrapped foam sheets may be laid directly layer by layer, or in two adjacent foam sheets, such that one foam sheet is a fully-wrapped foam sheet and the other foam sheet is a partially-wrapped foam sheet, and the surface of the partially-wrapped foam sheet in contact with the fully-wrapped foam sheet is not covered with a film; in step (4), providing composite ribs between the slit approximate flat areas; in the present invention, it is preferable that the composite material ribs are also provided at positions where corners are large; in the invention, the arrangement of the ribs of the composite material is beneficial to enabling the laid cladding foam sheet to be more similar to the structure of an actual product; in the invention, the material adopted by the ribs of the composite material is consistent with the material adopted by the inner bearing skin and the outer bearing skin; the setting mode of the composite material rib is as follows: and (3) filling the prepreg at the position corresponding to the composite material rib, and forming the composite material rib at the filling position after the pre-compaction in the step (4) and the step (5).
According to some preferred embodiments, when laying up a plurality (plural) of coated foam sheets layer by layer in each approximately flat area, the thickness of the coated foam sheets is not more than 5mm, preferably 2 to 4mm; in the present invention, the thickness of the coated foam sheet is preferably controlled to be not more than 5mm, more preferably 2 to 4mm, and in the case where the thickness of the foam core portion of the foam core composite structure is large, it is necessary to embed a plurality of layers of coated foam sheets having a thickness of 2 to 4mm layer by layer in the thickness direction, and the layers are bonded by the coated adhesive film so as to better follow the shape, but there is no particular limitation on the thickness of the foam sheet laid on the flat plate structure portion included in the foam core portion.
According to some preferred embodiments, when the foam sandwich composite material structure is large in size, the foam sandwich portion is formed by splicing a plurality of coated foam blocks in the plane direction and/or the curved direction; the invention does not limit the specific dimension of the large dimension, namely, in the invention, when the dimension of the foam sandwich composite material structure is larger, the foam sandwich composite material structure is formed by splicing a plurality of coated foam blocks in the plane direction and/or the curved surface direction of the foam sandwich part according to the requirement.
According to some preferred embodiments, the prepreg is made of carbon fibers impregnated with epoxy resin, the carbon fibers are unidirectional T300, T700, T800, T1000, M40J or M55J carbon fibers, the epoxy resin is medium temperature cured epoxy resin, high temperature cured epoxy resin or bismaleic resin, in the present invention, taking "T700 carbon fibers" as an example, and referring to T700 carbon fibers or carbon fibers of the same class as T700; and/or the foam adopted by the foam sandwich part is PMI foam or polyurethane foam; in the invention, the adhesive film can be selected from adhesive films of the same resin system of the composite material, namely, the matched adhesive film is selected according to the prepreg resin system, for example, the intermediate temperature epoxy resin system can be selected from J-47A adhesive film or other intermediate temperature epoxy adhesive films, and if the high temperature epoxy resin system or other resin system is adopted, the matched other adhesive films and the matched curing system are selected.
According to some preferred embodiments, when the epoxy resin employed in the prepreg is a medium temperature cure epoxy resin, the pre-compaction is: sequentially laying release cloth and airfelt on the surface of a member to be pre-compacted, then placing the member into a vacuum bag, and pre-compacting the member by a vacuum bag method, wherein the pre-compacting temperature is 40-50 ℃ and the pre-compacting time is 20-40 min; and/or in the step (5), when the epoxy resin adopted in the prepreg is a medium-temperature curing epoxy resin, curing and forming are preferably performed by an autoclave, wherein the curing and forming temperature is 120-130 ℃, the curing and forming pressure is 0.4-0.6 MPa, and the curing and forming time is 2-4 hours, preferably 2 hours.
According to some preferred embodiments, the flat-shaped cladding foam sheet laid in the approximate flat area is made to approach to the mold shape under the action of vacuum pressure in the pre-compaction process; in the solidifying and forming process, the cladding foam sheet is adhered to the inner and outer bearing skins by using the pressure of an autoclave, and meanwhile, the flat cladding foam sheet approaching to the following mold is adhered to the following mold surface.
According to some specific embodiments, the specific process of the forming method of the foam sandwich composite material structure is, for example:
(1) according to the composite material solid part and the foam sandwich part in the foam sandwich composite material structure to be prepared, the foam sandwich part arranged in the composite material is decomposed into a plurality of foam flat plates (foam thin plates) which are spliced, and the thickness of the foam flat plates can be the same and/or different; cutting out a prepreg sample (prepreg sample) according to the structural shape of the foam sandwich composite material to be prepared; a molding die (molding die) for curing and molding is machined according to the structural shape of the foam sandwich composite material to be prepared.
(2) The foam sheet stock is cut into foam sheets required for layering.
(3) Firstly, paving a whole layer of prepreg in a molding die to form a side bearing skin (outer bearing skin); when the central position of the foam sandwich composite material structure is also required to be provided with other core block components, the position of the reserved mould core block is cut off when the whole prepreg is paved integrally to form a one-side integral bearing skin, for example, when the central position (the middle position of a product) of the foam sandwich composite material structure is provided with a mouth frame, the position of the reserved mould core block is cut off when the whole prepreg is paved integrally to form a one-side integral bearing skin, namely, the foam sandwich composite material structure is obtained through space occupying molding of the mould core block.
(4) And (3) pre-compacting and semi-curing the prepreg laid in the die in the step (3).
(5) Wrapping (cladding) the foam sheet with a glue film of the same resin system as the composite material to obtain a clad foam sheet and laying the clad foam sheet at the position of the foam sandwich part, wherein the rest positions can lay down the prepreg according to structural characteristics, and the rest positions can properly reduce the thickness of the prepreg according to structural requirements; in the step (1), the position of the foam molding with a non-flat plate structure needs to be cut, and the position with smaller corner angle or partial arc shape is cut; in the step (5), proper composite material rib separation can be added in the middle of the cut coated foam plates so as to achieve the approximate structure of the foam sheet and the actual product; when the size area of the foam sheet required by the product is overlarge, a plurality of foam sheets can be spliced in a butt joint manner in the plane direction and/or the curved direction; the thickness of the foam sheet laid at the non-flat plate structure position is preferably controlled to be not more than 5mm, the foam sheet needs to be cut into multiple layers along the thickness direction under the condition of larger required thickness, and the layers are bonded through the adhesive film coating the foam sheet so as to be better along with the foam sheet, and the foam sheet at the flat plate structure position has no thickness limitation.
(6) And pre-compacting and semi-solidifying again.
(7) Laying a whole layer of prepreg to form a bearing skin (inner bearing skin) on the other side; in the present invention, the outer load-bearing skin and the inner load-bearing skin may be collectively referred to as load-bearing skin.
(8) And cooling and demolding after heating, solidifying and forming. In the molding process, the cladding foam sheet and the molded surface of the mold are completely along with each other under the action of pressure, and the bonding surface of the cladding foam sheet and the bonding surface of the composite material are bonded through an adhesive film, so that the bonding quality is ensured, and an integrally molded composite material foam sandwich structure is obtained; in the present invention, for example, as shown in fig. 1, 2 and 3, the foam sandwich composite structure sequentially includes an outer load-bearing skin, an inner load-bearing skin, and a sandwich structure disposed between the outer load-bearing skin and the inner load-bearing skin, the sandwich structure including a composite solid portion including a plurality of laid-up coated foam sheets and composite ribs disposed at slits, and a foam sandwich portion for covering a foam outer edge of the foam sandwich portion to prevent the foam sandwich portion from being exposed.
The forming method is suitable for various composite material systems, and comprises the steps that the composite material system reinforcing fibers are selected from high-strength medium-mode carbon fibers, such as T300 level, T700 level, T800 level, T1000 level and the like, or selected from high-strength high-mode carbon fibers, such as M40J level, M55J level and the like; the resin system of the composite material is selected from medium-temperature epoxy, high-temperature epoxy, bismaleimide resin and the like; PMI foam, polyurethane foam and the like are selected as the foam, and the curing process parameters can be determined according to the selected materials. The forming method is suitable for various forming processes such as autoclave, compression molding, expansion mold forming and the like. The forming method is also suitable for the sandwich composite material with a structure similar to the same thickness, and can be decomposed into a composite material skin and a foam sandwich on two sides with similar thickness.
The foam sheet used in the invention is only required to form flat plates with different thicknesses in the thickness direction, and then the flat plate is cut after two-dimensional drawing design is carried out according to the modeling, so that three-dimensional complex modeling processing is not required. The invention uses the pressure applied in the pre-compaction semi-curing and curing process to make the foam sheet and the mould follow up, thereby obtaining the product shape.
According to some preferred embodiments, the foam core composite structure is a foam core composite flap structure, for example, as shown in fig. 1, 2 and 3, the foam core portion of the foam core composite flap structure includes a foam core flat plate portion and foam core arc plate portions located at two sides of the foam core flat plate portion, and the foam core flat plate portion and the foam core arc plate portion are in smooth transition connection.
According to some preferred embodiments, the foam sandwich arcuate plate section is slit into a plurality of approximate flat plate areas, with composite material ribs disposed between the approximate flat plate areas and/or between the approximate flat plate areas and the foam sandwich flat plate section, as shown, for example, in fig. 3; in the invention, the foam sandwich composite material flap structure sequentially comprises an outer bearing skin, an inner bearing skin and a sandwich structure arranged between the outer bearing skin and the inner bearing skin, wherein the sandwich structure comprises a composite material solid part and a foam sandwich part, the foam sandwich part of the foam sandwich composite material flap structure comprises a foam sandwich flat plate part and foam sandwich arc plate parts positioned at two sides of the foam sandwich flat plate part, the foam sandwich flat plate part is in smooth transition connection with the foam sandwich arc plate parts, the foam sandwich flat plate part lays a layer of coated foam sheet, the foam sandwich arc plate parts positioned at two sides respectively comprise a plurality of approximate flat plate areas which are cut, and the coated foam sheet is laid layer by layer in the thickness direction of each approximate flat plate area until reaching the thickness of the preset approximate flat plate area; composite ribs are arranged between the approximate flat plate areas and the foam sandwich flat plate parts; the foam sandwich panel portion lays down a coated foam sheet having a thickness of 5-10 mm (e.g., 5, 6, 7, 8, 9 or 10 mm); and/or laying a plurality of coated foam sheets with the thickness of 2-4 mm (for example 2, 3 or 4 mm) layer by layer in the approximate flat area until the preset approximate flat area thickness is reached.
The present invention provides in a second aspect a foam sandwich composite structure formed by the forming method of the invention described in the first aspect.
The invention is further illustrated below with reference to examples. These examples are merely illustrative of preferred embodiments of the present invention and the scope of the present invention should not be construed as being limited to these examples only.
Example 1
The present embodiments provide a foam sandwich composite material flap structure, for example, as shown in fig. 1, 2 and 3; the foam sandwich composite material covering cap structure sequentially comprises an outer bearing skin, an inner bearing skin and a sandwich structure arranged between the outer bearing skin and the inner bearing skin, wherein the sandwich structure comprises a composite material solid part and a foam sandwich part, the foam sandwich part of the foam sandwich composite material covering cap structure comprises a foam sandwich flat plate part and foam sandwich arc plate parts positioned at two sides of the foam sandwich flat plate part, the foam sandwich flat plate part is in smooth transition connection with the foam sandwich arc plate parts, the foam sandwich flat plate part is paved with a layer of cladding foam thin plate with the thickness of 6mm, the foam sandwich arc plate parts positioned at two sides comprise two cut approximate flat plate areas, and two layers of cladding foam thin plates with the thickness of 3mm are paved layer by layer in the thickness direction of each approximate flat plate area; composite ribs are arranged between the approximate flat plate areas and the foam sandwich flat plate parts; the coating foam sheet is formed by coating a film on the foam sheet; the foam sheet and the coated foam sheet are both flat.
In the embodiment, the T800-grade/medium-temperature epoxy prepreg (T800/9368 unidirectional epoxy resin prepreg), a medium-temperature epoxy adhesive film (J-47A adhesive film) and PMI foam are used as raw materials to form the foam sandwich composite material flap structure. Cutting out a prepreg for an outer bearing skin and a prepreg for an inner bearing skin according to the structural shape of a to-be-molded foam sandwich composite material covering cap, cutting out a prepreg for a solid part of a composite material according to the structural shape of the to-be-molded foam sandwich composite material covering cap, and machining a molding die (a molding die) for curing molding according to the structural shape of the to-be-prepared foam composite material covering cap; the curing mode adopts a molding mode of a single-sided die of an autoclave. The mold surface identifies the product boundary by scoring.
The molding method of the foam sandwich composite material flap structure comprises the following steps:
(1) parting is carried out according to the structure of the foam sandwich composite material flap to be molded, as shown in fig. 3; the foam sandwich part comprises a foam sandwich flat plate part and a foam sandwich arc plate part, the foam sandwich arc plate part is cut, a plurality of approximate flat plate areas are cut, each approximate flat plate area is decomposed into double-layer foam flat plate narrow strips (foam thin plates) with the thickness of 3mm+3mm, and composite material ribs are designed between the approximate flat plate areas, the approximate flat plate areas and the foam sandwich flat plate part to separate the foam thin plates, so that the foam thin plates are approximately molded with a die, and a foam drawing is drawn; in this embodiment, the foam sheets for laying are coated with a layer of adhesive film on the surface.
(2) Cutting the raw material of the foam sheet into foam sheets with the thickness of 6mm and 3mm, wherein the length and the width of the foam sheets are not required, and only the thickness of the foam sheets is regulated; and cutting the prepreg and the foam sheet according to the drawing.
(3) And (3) integrally paving the prepreg in a molding die to form an integral bearing skin on one side.
(4) Pre-compacting: and (3) laying release cloth and airfelt on the surface of the prepreg in sequence, putting the prepreg into a vacuum bag, bonding the prepreg through a sealing adhesive tape to ensure air tightness, pre-compacting and semi-curing the prepreg by adopting a vacuum bag method, putting the prepreg into an oven, and heating to 40 ℃ for heat preservation for 30min.
(5) Wrapping the surface of the foam sheet with a medium-temperature epoxy adhesive film, then laying the foam sheet at the position of a foam sandwich part, and filling prepregs for forming composite material ribs between the approximate flat areas and the foam sandwich flat parts; the prepreg is laid in the solid part of the rest composite material and connected with the foam sheet, and the edge reaches the same height as the foam sheet.
(6) And (3) carrying out pre-compaction treatment again by adopting a vacuum bag method at the temperature of 40 ℃ for 30min, and enabling the foam sheet which is originally flat to approach to a die under the action of pressure under the vacuum pressure.
(7) After the pre-compaction treatment of the step (6), the prepreg is integrally paved again to form the integral bearing skin on the other side.
(8) Heating, curing and forming the material laid in the die for forming by adopting an autoclave, controlling the temperature to 130 ℃, controlling the curing pressure to 0.5MPa, and curing and forming for 2 hours; and (3) bonding the foam sheet and the composite material bearing skin by using autoclave pressure in the curing process, and simultaneously enabling the foam sheet and the mold to completely follow, and demolding to obtain the foam sandwich composite material flap structure.
The invention is not described in detail in a manner known to those skilled in the art.
The last explanation is: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in each embodiment can be modified or part of technical features in the technical scheme can be replaced equivalently; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A method of forming a foam sandwich composite material structure, the method comprising the steps of:
(1) Dividing a foam sandwich composite material structure to be formed into a composite material solid part and a foam sandwich part, decomposing the foam sandwich part into a plurality of foam thin plates which are spliced, cutting the foam thin plates into a plurality of foam thin plates, and coating the foam thin plates with an adhesive film to obtain coated foam thin plates; the foam sheet and the coated foam sheet are flat;
(2) Cutting out prepreg for the outer bearing skin according to the structural shape of the foam sandwich composite material to be formed, prepreg for the inner bearing skin, and preparing a forming die according to the structural shape of the foam sandwich composite material to be formed;
(3) Paving a prepreg for the outer bearing skin in a molding die and pre-compacting to obtain an outer bearing skin prefabricated member;
(4) Laying a cladding foam sheet at the position of a foam sandwich part and pre-compacting to obtain a sandwich structure prefabricated member on the upper surface of the outer bearing skin prefabricated member;
(5) And (3) paving prepreg for the inner bearing skin on the upper surface of the prefabricated member of the sandwich structure, and then performing curing molding and demolding to obtain the foam sandwich composite material structure.
2. The molding method according to claim 1, wherein:
in the step (1), when the foam sandwich portion includes a non-flat plate structure, cutting the position of the non-flat plate structure, and cutting the position with smaller corners or partial arc shape to obtain a plurality of approximate flat plate areas;
in step (4), laying at least one coated foam sheet layer by layer in the thickness direction of each approximate flat area until reaching the preset approximate flat area thickness;
in step (4), composite ribs are provided between the slit approximately flat areas.
3. The molding method according to claim 2, characterized in that:
when a plurality of coated foam sheets are laid layer by layer in each approximately flat area, the thickness of the coated foam sheet is not more than 5mm, preferably 2 to 4mm.
4. The molding method according to claim 1, wherein:
when the foam sandwich composite material structure is large in size, the foam sandwich part is formed by splicing a plurality of coated foam blocks in the plane direction and/or the curved surface direction.
5. The molding method according to claim 1, wherein:
the prepreg is prepared by impregnating carbon fibers with epoxy resin, wherein the carbon fibers are unidirectional T300-level, T700-level, T800-level, T1000-level, M40J-level or M55J-level carbon fibers, and the epoxy resin is medium-temperature cured epoxy resin, high-temperature cured epoxy resin or bismaleimide resin; and/or
The foam adopted by the foam sandwich part is PMI foam or polyurethane foam.
6. The molding method according to claim 1, wherein:
the pre-compaction is as follows: sequentially laying release cloth and airfelt on the surface of a member to be pre-compacted, then placing the member into a vacuum bag, and pre-compacting the member by a vacuum bag method, wherein the pre-compacting temperature is 40-50 ℃ and the pre-compacting time is 20-40 min; and/or
In the step (5), curing and forming are carried out by an autoclave, wherein the temperature of curing and forming is 120-130 ℃, the pressure of curing and forming is 0.4-0.6 MPa, and the time of curing and forming is 2-4 h.
7. The molding method according to claim 6, wherein:
in the precompaction process, the flat cladding foam sheet laid in the approximate flat area is made to approach to the following mold under the action of vacuum pressure;
in the solidifying and forming process, the cladding foam sheet is adhered to the inner and outer bearing skins by using the pressure of an autoclave, and meanwhile, the flat cladding foam sheet approaching to the following mold is adhered to the following mold surface.
8. The molding method according to any one of claims 1 to 7, characterized in that:
the foam sandwich composite material structure is a foam sandwich composite material covering cap structure, a foam sandwich part of the foam sandwich composite material covering cap structure comprises a foam sandwich flat plate part and foam sandwich arc plate parts positioned on two sides of the foam sandwich flat plate part, and the foam sandwich flat plate part is in smooth transitional connection with the foam sandwich arc plate parts.
9. The molding method according to claim 8, wherein:
cutting a plurality of approximate flat plate areas on the foam sandwich arc plate part, and arranging composite material ribs between the approximate flat plate areas and/or between the approximate flat plate areas and the foam sandwich flat plate part;
the foam sandwich flat plate part is paved with a coated foam sheet with the thickness of 5-10 mm; and/or
And laying a plurality of coated foam thin plates with the thickness of 2-4 mm layer by layer in the approximate flat area until the thickness of the preset approximate flat area is reached.
10. A foam sandwich composite structure formed by the forming method of any one of claims 1 to 9.
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