JP4229216B2 - Integrated composite structure - Google Patents

Description

[0001]
Detailed Description of the Invention
TECHNICAL FIELD OF THE INVENTION The present invention relates to the production of a fiber reinforced resin composite structure, and more particularly to a resin transfer molding method with the aid of vacuum (vacuum decompression) of a large composite structure.
[0002]
Background of the invention Vacuum assisted resin transfer molding (VA-RTM) is a number of large, fiber reinforced, such as boat hulls incorporating structural materials such as foam cores and balsa cores. Used in the manufacture of composite structures. The core is covered with a fiber reinforced resin. In the VA-RTM process, reinforcing fibers such as fabrics or mats are placed in a single mold in a dry state with the desired core material according to the shape of the desired finished part. Next, this combination is sealed in a vacuum bag and impregnated with resin by a vacuum action. The resin then cures.
[0003]
Various methods are used to introduce the resin into the reinforcing fibers and improve the distribution of the resin. These methods include placing a disposable distribution medium across the outer layer of fibers and employing holes and / or slots through the core to allow the resin to flow from the outer layer to the inner layer of the reinforcing fibers. Is done. See, for example, US Pat. Nos. 5,316,462 and 4,560,523. The supply groove in the foam core is also used in the process of closing the mold and injecting the resin in order to make the resin flow smooth. See, for example, US Pat. No. 5,096,851.
[0004]
SUMMARY OF THE INVENTION The present invention relates to a method of dispensing a resin and a composite structure made by this method during the manufacture of large composite structures using vacuum assisted resin transfer molding (VA-RTM). It is about the body. The composite structure is formed from an inner core surrounded by a resin reinforced with fibers. In one embodiment of the invention, resin is fed directly into a main feed groove connected to a network of a plurality of fine microgrooves formed on the outer surface of the inner core. The resin fed from the feeding groove and the fine groove flows outward from the core through the contact point between the groove and the fiber and penetrates into the reinforcing fiber. In a second embodiment of the invention, a separate distribution medium is interposed between the inner core and the reinforcing fibers. The resin is directly supplied to one or a plurality of main feeding grooves on the surface of the core, and the resin penetrates into the reinforcing fiber through the distribution medium. The main feed groove forms a supply loop that feeds the resin around the core, and impregnates the structural member in the transverse direction of the core.
[0005]
In a further embodiment, an integrated vacuum bag and mold are formed from a sheet of metal textured skin. This textured skin is formed by ridges that are in close proximity to one side of the sheet, which are recessed on the other side of the sheet. Closely raised ridges create a gap between them, which form a resin distribution network. The sheet of textured skin can also be used as a mold to make another tool.
[0006]
By this method, a large composite structure requiring a large number of cores can be quickly molded before the typical vinyl ester resin or polyester resin is gelled, and the amount of resin used can be reduced. By supplying directly to the feed groove using a vacuum bag, this supply is not limited to the edge part of the part or the entrance of the tool. Adjacent cores can be fed through a single resin inlet. The main distribution network can be left in the finished part and the distribution material is not discarded. In this case, the fine groove is filled with the resin after being cured, thereby improving the interlaminar shear strength and the delamination strength. Structural features such as shear ties, compression webs or beams can be incorporated directly into the composite part during the molding process.
[0007]
DESCRIPTION OF THE DRAWINGS The invention will be more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a perspective view of a core for a composite structure according to a first embodiment of the present invention;
2 is a schematic cross-sectional view of a composite structure formed according to the first embodiment of the present invention;
3 is a schematic perspective view of another composite structure formed in accordance with the present invention;
4 is a perspective view of another composite structure formed in accordance with the present invention;
FIG. 5 is a perspective view of another core of a composite structure according to the present invention;
6 is a perspective view of a core of a composite structure according to a second embodiment of the present invention;
FIG. 7 is a schematic cross-sectional view of a composite structure formed in accordance with a second embodiment of the present invention;
FIG. 8 is a schematic cross-sectional view of a composite structure formed using an integrated mold and vacuum structure;
FIG. 9 is a schematic cross-sectional view of a rigid mold and flexible lid to form a composite structure;
FIG. 10 is a perspective view of a core for a composite structure having a number of main feed grooves;
FIG. 11 is a schematic cross-sectional view of an integrated mold and vacuum bag for forming a composite structure according to a further embodiment of the present invention;
12 is a perspective view of one side of the sheet of fabric skin of the material forming the integrated mold and vacuum bag of FIG. 11;
FIG. 13 is a perspective view of the other surface of the textured sheet of FIG.
[0008]
DETAILED DESCRIPTION OF THE INVENTION A large composite part (part) made in accordance with the present invention includes a core 12, as shown in FIG. The core is made of a material that can withstand reduced pressure. Typical of these materials include foams or balsa materials such as polyurethane or polyvinyl chloride. The core may be a solid molded product or a hollow molded product made of blow molded polyethylene. Concrete can also be used. The core is illustrated as a rectangular shape, but other shapes may be used as described below.
[0009]
The surface 16 of the core is provided with a channel 14 which is one or more feeding grooves. The main feed groove surrounds the entire core and forms a loop. A network that distributes resin composed of channels having a smaller cross-sectional area than the main feeding groove is provided in contact with the surface of the core, and the network is in fluid communication with the main feeding groove.
[0010]
In the first embodiment of the present invention, the resin distribution network is provided in the form of a number of fine grooves 18 formed by grinding the surface 16 of the core 12 as shown in FIG. The fine grooves 18 are generally arranged so as to be orthogonal to the main feeding groove 14. Some of the fine grooves surround the entire core so as to create a resin flow loop starting from the main feed groove 14 and ending with this groove.
[0011]
The actual relationship of the fine grooves with respect to the main feed groove is determined in that the core contour shape and the resin impregnation are most effectively performed as described below.
[0012]
The core with the groove network is coated with a single layer or multiple layers of fiber material 20 as schematically shown in FIG. The fiber material may be a woven fabric or mat formed from glass fiber, carbon fiber or other suitable material. Depending on the structural requirements of the desired final part (part), the core may be completely surrounded by fiber material, or one or more surfaces of the core may be free of fiber material. The fiber material may be wrapped around the core as a sheet, or each fiber material may be attached to a desired surface of the core. The fibers may also be supplied in the form of a tube into which the core is inserted.
[0013]
The cores wrapped with a plurality of fiber materials are arranged to form the desired final part. Although two cores are shown in FIG. 2, the number and arrangement of core implementations is determined by the desired final part. As shown schematically in FIG. 2, the outer layer 22 can be formed by wrapping a plurality of cores with single or multiple layers of fibrous material.
[0014]
The particular number, type and arrangement of fibrous layers can be determined by the desired end piece, which can be readily determined by those skilled in the art. A drainage layer is provided in the form of a tab 23, which extends from the outer layer of fibers to the vacuum outlet 25. The release layer normally required for prior art vacuum forming processes is generally not necessary for the process of the present invention.
[0015]
The fibrous material 24 surrounding and between the plurality of cores forms structural members such as shear ties, compression webs and girders. For example, as shown in FIG. 4, a deck is formed using a plurality of triangular cores 40. The fiber material between adjacent triangular cores forms a diagonal structural member 41 that bears both compressive and shear forces.
[0016]
During a fiber layup operation, a suitable mounting piece 26, such as a plastic T-piece or copper T-piece, is positioned in the main feed channel 14 and the resin supply tube 28 is moved back. Easy to insert from. One or a plurality of attachment parts are positioned in each feed groove to facilitate a desired resin flow. The laid-up fiber material is placed against the mold 29, and then the vacuum bag 30 is placed over the laid-up material including the plastic mounting parts as shown schematically in FIG. The mold is sealed in an embodiment. The vacuum bag is then pierced, and the resin supply tube 28 is squeezed directly into the respective attachment component 28 via the vacuum bag. Seal the supply tube to the bag to maintain vacuum maintenance. In such an embodiment, since the resin supply tube inserted directly into the main feeding groove penetrates the outer vacuum bag, the resin also penetrates, and the resin is directly supplied to the main feeding groove. The
[0017]
Referring to FIG. 8, the vacuum bag and the mold are integrated into a single structure 80, and the structure, as a mold, has sufficient robustness to maintain its shape, When evacuated, it collapses at atmospheric pressure, thereby being flexible enough to cover the part. For example, the integrated structure 80 may comprise a thin gauge steel sheet, for example, 0.635 cm (0.25 inch) or thinner. The core 82 and the fiber materials 84 and 86 as described above are wrapped in the steel sheet. A hole is drilled in the sheet to access the mounting part. Resin impregnation is performed as described above. The integral structure can be formed of another suitable material such as rubber, silicon or plastic laminated metal.
[0018]
FIG. 9 shows another mold embodiment in which the rigid mold 90 is sealed with a flexible lid 92 made of, for example, steel or plastic. A part (part) composed of a plurality of cores and fiber materials as described above is placed in a recess 94 defined by a hard mold. A vacuum groove 96 in the lid surrounds the part. A hole penetrates the lid or mold and connects to the mounting part for resin impregnation as described above. While the resin is impregnated while being evacuated, the lid is bent at the edge of the vacuum groove to consolidate the parts.
[0019]
Resins such as polyester, vinyl ester, epoxy, phenol, acrylic or bismaleimide flow through the main feed groove 14 relatively quickly and reach the fine groove 18. The resin penetrates into the fiber materials 20 and 22 from the fine groove. The resin overflows from the surface 16 of the core and moves outward to the outside of the part, thereby completing the impregnation. As shown in FIGS. 3 and 4, the fiber material on the surface of the adjacent core is impregnated through the main feeding groove on one of the adjacent cores.
[0020]
Optimizing the cross-sectional area of the main feed groove and the cross-sectional area and spacing of the fine grooves, and before curing (curing), all of the fiber material is impregnated with resin without leaving an unimpregnated area Set an appropriate time to A typical main feed groove having a cross-sectional area of 1.61 cm ² (0.25 in ² ) has a depth of 1.27 cm (0.5 in) and a width of 1.27 cm (0 .5 inches). Typical microgrooves, in what is a cross-sectional area of about 0.103cm ² (about 0.016 square inches), at a depth of 0.318 cm (0.125 inches), a width of 0.318 cm (0. 125 inches). The fine grooves are separated by a space of 2.54 cm (1.0 inch) at the center. These dimensions are modified to accommodate reinforcing fiber materials having different types and / or fineness. Also, if the part is particularly large and the resin is distributed more quickly to all sections of the part, the cross-sectional area of the main feed groove can be increased. Similarly, a plurality of main feeding grooves 14 can be added to the core 12 as shown in FIG.
[0021]
Furthermore, the flow can be limited so that the cross-sectional area of the main feed groove or fine groove is reduced and the resin residence time in the specific area is extended. The resin residence time can also temporarily block the resin flow by placing a resin fuse in the feed groove. The resin fuse melts when it touches the resin after a predetermined time that can be set by the length of the fuse. For example, for vinyl ester resins, styrofoam (expanded polystyrene) can be used successfully. The feeding groove can also be terminated to change the direction of resin flow.
[0022]
After impregnation, the resin is allowed to cure with sufficient time. Once cured, the microgroove 18 is filled with a hard resin. This resin provides a side locking mechanism that improves the interlaminar shear strength of the bond between the fiber reinforced composite and the core. Resin that remains in the groove network also enhances the force required to delaminate the skin layer on the fiber reinforced surface from the core.
The actual arrangement, shape and number of cores will depend on the desired final part.
[0023]
For example, a triangular core 40 is shown in FIG. These triangular cores have a main feed groove 42 on at least two surfaces. The central triangular core 44 has main feed grooves on three sides. A plurality of triangular cores, for example, are arranged in rows to form a deck. In this example, the resin supplied through the tube 46 begins to impregnate starting from the central core, sequentially impregnated, and impregnated into the edge portion as indicated by the shaded region 48 in FIG.
[0024]
An arcuate core 50 is shown in FIG. The arcuate core 50 has a main feed groove 52 on one surface and a network of fine grooves 54 extending radially from the feed groove and surrounding the core. The arched core is used to form a curved structure such as a boat hull or arch.
[0025]
In another embodiment of the present invention shown in FIGS. 6 and 7, the core 60 is provided with the main feeding groove 62 as described above. A distribution medium 64 is then provided proximate to the core surface. The medium is formed of a networked open passage, and the passage is formed by a structure capable of maintaining the passage in an open state while being evacuated. For example, the medium is an intersecting fiber that is held away from the surface of the core by a post-like member at the intersecting position of the fiber, an aligned lattice-like structure, or It consists of an open woven textile fabric. Suitable distribution media are known, for example, from US Pat. Nos. 4,902,215; 5,052,906, incorporated herein by reference. The distribution medium is then wrapped with fiber material 66 as described above. A plurality of cores are arranged to form the desired final part, and the vacuum bag 68 is placed over the core and fiber material as described above. A resin supply tube 70 connected from a resin supply source is passed through the bag 68 and the fiber material 66 and attached to an attachment part 72 in the main feed groove 62. The supply tube 70 is sealed to the vacuum bag in a manner known in the art. The resin is sent to the main feeding groove through the supply tube. The resin passes through the main feed channel relatively quickly and reaches the distribution medium. Thereafter, the resin penetrates the fiber material through the distribution medium. The resin hardens after an appropriate time. Due to the resin distribution medium, the resin flows more uniformly forward than by the fine grooves. For this reason, resin distribution media are generally preferred for even more complex parts, whereas microgrooves are suitable for resin savings because of the low flow rate of resin flowing through the microgrooves.
[0026]
In a further embodiment, shown in FIGS. 11-13, the vacuum bag and mold are integrated as a mold 112 with a sheet 104 in the form of a metal fabric such as a thin gauge steel sheet. The sheet has sufficient rigidity to maintain its shape as a mold, but as described below, it is crushed or pulled against a piece under a vacuum that is pulled during the resin impregnation process. It is flexible enough to be able to be A sheet thickness of 0.64 cm (0.25 inch) or less has been found suitable. Composite materials such as plastic formed as a woven sheet or a laminate of metal and plastic can also be used.
[0027]
The woven fabric is preferably formed by raised portions 108 formed on one surface of the sheet 104 at a close interval, which correspond to the recessed portions 106 on the other surface of the sheet. The densely raised ridges 108 define a gap 110 between them, which forms a network of resin distribution. For example, the ridge has a generally hexagonal shape, with the longest dimension being from 0.95 cm (3/8 inch) to 1.11 cm (7/16 inch). It has been found that a suitable depth of the gap is 0.0762 cm (30 / 1000th of an inch). Such woven sheets are easily foamable and are commercially available from Ardmore Textured Metal of Edison, New Jersey. Alternatively, the textured surface can be provided on one side of the sheet, if desired, in which case the raised portion does not create a recess corresponding to the other surface.
[0028]
The sheet is shaped into a mold 112 of the desired foam having a mold cavity 118, and the raised portion of the sheet forms the inner wall of the cavity and faces the part to be impregnated. The main feed groove 114 is provided directly at a desired location on the sheet 104 without being provided on the core as described above. The dimensions of the main feed groove are as described above. A vacuum exhaust channel 116 is provided around the tool.
[0029]
To form a piece, a fiber layup is placed in the cavity 118 proximate the textured surface of the tool and the tool is sealed with adhesive tape or other art-known seal. A release layer can be used when the woven ground should not be secured to the piece. Otherwise, the release layer may be omitted when the woven ground should be secured to the piece. By making a woven ground on the part, the strength of the part is increased, which is also desirable in terms of aesthetics. The fiber layup includes a core wrapped with a fiber material, as described above. Insert the attachment part into the main feed groove from the hole made in the sheet as described above, pull the vacuum inside the tool and pull the sheet of woven material closer to the fiber layup, The top of the ridge contacts the fiber layup, but the gap remains open, forming a thin, interconnected passage through which resin can flow. Under the pressure reducing action, the resin is first drawn into the main feed groove and then drawn into the gap. The resin is completely impregnated into the fiber material from the gap and finally flows to the vacuum outlet channel surrounding the periphery. The resin hardens after a sufficient time. After curing, the part is removed from the tool.
[0030]
In another embodiment, the woven sheet can be used as a lid for a normal mold. Place the fiber layup on the surface of the mold. A woven sheet is placed over the fiber layup and sealed to the mold in an appropriate manner. It is necessary to add and use a resin distribution medium in close proximity to the surface of the conventional mold. The impregnation of the resin is performed as described above.
[0031]
The textured sheet can also be used as a matrix used to make tools from other materials such as ceramics. The tool is then used as a mold in a resin impregnation process. In this case, the sheet becomes the negative of the tool; that is, the surface of the sheet with indented portions forms the tool. The tool thus formed has a raised portion shape separated by a gap, and the raised portion forms a resin distribution medium as described above. In general, ceramic molds do not flex and do not become crushed against parts even when pulled in a vacuum. In this case, another vacuum bag is used for the mold, as is known in the art.
[0032]
The invention is not to be limited to what has been particularly shown and described, except as indicated by the appended claims.
[Brief description of the drawings]
[0033]
1 is a perspective view of a core for a composite structure according to a first embodiment of the invention;
2 is a schematic cross-sectional view of a composite structure formed in accordance with a first embodiment of the present invention;
3 is a schematic perspective view of another composite structure formed in accordance with the present invention;
4 is a perspective view of another composite structure formed in accordance with the present invention;
FIG. 5 is a perspective view of another core of a composite structure according to the present invention;
6 is a perspective view of a core of a composite structure according to a second embodiment of the present invention;
7 is a schematic cross-sectional view of a composite structure formed in accordance with a second embodiment of the present invention;
FIG. 8 is a schematic cross-sectional view of a composite structure formed using an integrated mold and vacuum structure;
9 is a schematic cross-sectional view of a rigid mold and a flexible lid for forming a composite structure;
FIG. 10 is a perspective view of a core for a composite structure having a number of main feed grooves;
FIG. 11 is a schematic cross-sectional view of an integrated mold and vacuum bag for molding a composite structure according to a further embodiment of the present invention;
12 is a perspective view of one side of a sheet of fabric skin that is the material forming the integrated mold and vacuum bag of FIG. 11;
13 is a perspective view of the other surface of the sheet of fabric texture of FIG. 12. FIG.

Claims (11)

An integrated composite structure in which a core and a fiber material including the following are integrally combined with a resin :
A core (12) having a core peripheral side surface (16) and a feed channel (14) comprising a groove for feeding resin, wherein the feed channel (14) is at least one of the core peripheral side surface (16). Said core (12) formed to cross the section;
A resin distribution network (18; 64) comprising a narrow groove which forms a network on the peripheral surface of the core and distributes the resin from the feeding channel to the fiber material (20);
A fiber material (20) that contacts and covers the core (12), the feed channel (14) and the resin distribution network (18; 64) at the core peripheral side surface (16); and
A resin formed by impregnating and curing the fiber material (20), the feed channel (14), and the resin distribution network (18; 64);
The resin distribution network (18; 64) is in contact with the core peripheral surface (16) and the feeding channel (14), and the fiber material (20) is a resin distribution network. (18; 64)
The resin distribution network (18; 64) includes a network of grooves formed on the surface of the core (12) communicating with the feeding channel (14), and the network of the grooves is the feeding channel ( The integrated composite structure according to 14), wherein the cross-sectional area is smaller than the cross-sectional area of the groove of 14) . 2. A structure according to claim 1, wherein the grooves of the resin distribution network (18; 64) are perpendicular to the feed channel (14) . The groove of the resin distribution network (18; 64) is formed in a loop around the core (12), the loop starting from the feed channel and ending with the feed channel. 1 or 2 structures. The core according to claim 1, further comprising a plurality of the cores, each core having a peripheral side surface and a feeding channel formed on the surface extending over the entire length of the core, wherein the cores are arranged close to each other. Structure. 5. The structure of claim 4, wherein the cores are disposed adjacent to each other and each of the arranged feed channels is provided. The structure according to claim 1, wherein the core is made of a foam. The structure according to claim 1, wherein the core is made of a balsa material. The structure according to claim 1, wherein the core is made of concrete. The structure according to claim 1, wherein the core includes a block having a substantially rectangular cross-sectional shape. The structure according to claim 1, wherein the core includes a block whose cross-sectional shape is approximately triangular. The structure of claim 1, wherein the core comprises a block having an arched surface.

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