RTM molding device, RTM molding method, and semi-molded body

Abstract

An RTM molding device and an RTM molding method which enable resin impregnation of even large members and thick members without causing non-impregnated regions or fiber wrinkle, and yield a molded body having superior toughness and excellent precision. In the RTM molding device, a surface molding layer, which is disposed between a fiber-reinforced base material and a molding die, has a plurality of through-holes formed therein, and has sufficient rigidity that the thickness does not substantially change under the pressure inside the cavity when the inside of the cavity is placed under reduced pressure, and a resin diffusion portion, which is located on the side of the surface molding layer opposite the fiber-reinforced base material, and comprises a resin flow path formed so as to connect with the plurality of through-holes of the surface molding layer, are provided on at least one surface of the fiber-reinforced base material.

Claims

1. An RTM molding device including: a molding die inside of which a cavity is formed; and a resin injection line and a suction line that are connected to the cavity, the device being configured such that a fiber-reinforced base material is placed in the cavity, pressure inside the cavity is reduced, and a resin composition is injected into the cavity to impregnate the fiber-reinforced base material and form a molded body, wherein the RTM molding device further comprises: a surface molding layer for molding a surface and being disposed between the fiber-reinforced base material and the molding die, the surface molding layer having a plurality of through-holes formed therein, and having sufficient rigidity so that thickness does not substantially change under a pressure inside the cavity when the inside of the cavity is placed under reduced pressure; and resin diffusion means located on a side of the surface molding layer opposite the fiber-reinforced base material, the resin diffusion means defining a resin flow path connecting with the plurality of through-holes of the surface molding layer and allowing the resin composition to pass therethrough, wherein the surface molding layer and the resin diffusion means are configured to be provided on at least one surface of the fiber-reinforced base material, wherein the resin diffusion means is composed of at least a first resin diffusion layer, which has a plurality of through-holes formed therein, the through-holes having a larger diameter than the through-holes formed in the surface molding layer, wherein the first resin diffusion layer has sufficient rigidity so that thickness does not substantially change under the pressure, and the first resin diffusion layer is disposed between the surface molding layer and the molding die, wherein the through-holes formed in the first resin diffusion layer connect with two or more of the through-holes formed in the surface molding layer to form the resin flow path, wherein the resin diffusion means is composed of a second resin diffusion layer disposed adjacent to the first resin diffusion layer, the second resin diffusion layer having a plurality of through-holes formed therein, and wherein the through-holes formed in the surface molding layer and the first resin diffusion layer are formed with a different shape from through-holes formed in the second resin diffusion layer.

2. The RTM molding device according to claim 1, wherein a diameter of the through-holes in the surface molding layer is not more than a predetermined value that ensures that a shape of the through-holes is not transferred to the molded body under a pressure that exists when the inside of the cavity is placed under reduced pressure.

3. The RTM molding device according to claim 1, wherein the resin diffusion means is provided on at least one surface of the fiber-reinforced base material, on a side from which the resin is injected or a side from which the resin is discharged, and when the resin diffusion means is provided on the side of the fiber-reinforced base material from which the resin is injected, the resin flow path is connected to the resin injection line, whereas when the resin diffusion means is provided on the side of the fiber-reinforced base material from which the resin is discharged, the resin flow path is connected to the suction line.

4. The RTM molding device according to claim 1, wherein the first resin diffusion layer is a porous plate formed from a punched metal.

5. The RTM molding device according to claim 1, wherein the surface molding layer is a porous plate formed from a punched metal.

6. The RTM molding device according to claim 1, wherein a diameter of the through-holes formed in the surface molding layer is not less than 0.3 mm and not more than 2 mm.

7. The RTM molding device according to claim 1, wherein the through-holes formed in the surface molding layer and the first resin diffusion layer are formed with a phase offset relative to through-holes formed in the second resin diffusion layer.

8. The RTM molding device according to claim 1, wherein the resin diffusion means further comprises a channel formed in a surface of the molding die on a side of the fiber-reinforced base material, and the channel is connected to the resin injection line and the through-holes of the second resin diffusion layer, thus forming the resin flow path.

9. The RTM molding device according to claim 1, wherein the resin diffusion means further comprises a channel formed in a surface of the molding die on a side of the fiber-reinforced base material, and the channel is connected to the suction line and the through-holes of the second resin diffusion layer, thus forming the resin flow path.

10. The RTM molding device according to claim 1, wherein the second resin diffusion layer is stacked on the first resin diffusion layer, and wherein each of the through holes formed in the second resin diffusion layer has a larger diameter than the through-holes formed in the first resin diffusion layer.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 A cross-sectional view of an RTM molding device according to a first embodiment.

(2) FIG. 2 A top view illustrating one example of a punched metal.

(3) FIG. 3 A top view illustrating one example of a punched metal.

(4) FIG. 4 A top view illustrating one example of a punched metal.

(5) FIG. 5 A cross-sectional view explaining the flow of resin.

(6) FIG. 6 A diagram illustrating one example of a C-shaped structural member.

(7) FIG. 7 A cross-sectional view of an RTM molding device according to a second embodiment.

(8) FIG. 8 A cross-sectional view of a conventional RTM molding device.

(9) FIG. 9 A cross-sectional view of a conventional RTM molding device.

(10) FIG. 10 A cross-sectional view of a conventional RTM molding device.

(11) FIG. 11 A cross-sectional view of a conventional RTM molding device.

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment

(12) In this embodiment, an RTM molding device and RTM molding method for molding a flat plate-shaped structural member are described.

(13) FIG. 1 illustrates a cross-sectional view of the RTM molding device 100 according to the present embodiment. The RTM molding device 100 according to this embodiment comprises a molding die 1, a resin injection line 2, a suction line 3, a surface molding layer 4, and a resin diffusion portion 5.

(14) The molding die 1 is composed of an upper die and a lower die. Joining the upper die to the lower die forms an internal cavity. A sealing member 6 is provided at the interface between the upper die and the lower die so that when the upper die and the lower die are joined together, the inside of the cavity is tightly sealed.

(15) The resin injection line 2 and the suction line 3 are provided in connection with the inside of the cavity. In FIG. 1, one end of the resin injection line 2 is positioned at the upper portion of one end face of the inside of the cavity, and one end of the suction line 3 is positioned at the lower portion of the other end face of the inside of the cavity.

(16) The surface molding layer 4 has a plurality of holes 7 that pass through the layer in the thickness direction. The hole diameter of the holes 7 is sufficiently small to ensure that the shape of the holes in the surface molding layer 4 is not transferred to the surface of the molded body, and is preferably not less than 0.3 mm and not more than 2 mm, and more preferably not less than 0.5 mm and not more than 1 mm. The hole opening rate is preferably set, for example, to a value of not more than 51%. The shape of the holes 7 may be selected as appropriate, and may be circular, oval, square, hexagonal or rectangular or the like. The arrangement of the holes 7 may be a staggered array or a lattice arrangement or the like, and may also be selected as appropriate.

(17) The surface molding layer 4 is formed from a material having sufficient rigidity that the thickness of the layer does not substantially change even when pressure is applied inside the cavity during resin impregnation. The surface molding layer 4 preferably uses a punched metal formed from stainless steel, aluminum, iron or copper or the like. The thickness of the surface molding layer 4 is typically from approximately 0.2 mm to 3 mm, preferably from 0.3 mm to 2 mm, and more preferably from 0.5 mm to 1 mm.

(18) In the present embodiment, the resin diffusion portion 5 is formed from a resin diffusion layer 8, which in FIG. 1 is composed of two stacked resin diffusion layers 8a and 8b.

(19) The lower resin diffusion layer 8a is stacked on the surface molding layer 4. A plurality of holes 9 that pass through the layer in the thickness direction are formed in the lower resin diffusion layer 8a. The hole diameter of the holes 9 is set to a larger diameter than the holes 7 formed in the surface molding layer 4. The hole opening rate of the lower resin diffusion layer 8a is preferably higher than the hole opening rate of the surface molding layer 4, with larger hole opening ratios being more advantageous during resin impregnation. When determining the dimensions of the holes 9, an important consideration is ensuring that the surface molding layer 4 does not fall into the holes 9 of the lower resin diffusion layer 8a during molding. For example, a good balance relative to the rigidity of the surface molding layer 4 must be achieved on the basis of the short diameter or short side length in the case of oval or rectangular holes, or the diameter or diagonal length in the case of circular or hexagonal holes. Accordingly, based on these hole dimension restrictions, there is a limit to the hole opening rate of the lower resin diffusion layer 8a.

(20) The shape of the holes 9 may be circular, oval, square, hexagonal or rectangular or the like, and is preferably selected so that the shape of the holes 9 differs from the shape of the holes formed in the surface molding layer 4. The arrangement of the holes 9 may be a staggered array or a lattice arrangement or the like, and may be selected as appropriate, but in order to ensure a phase difference relative to the holes 7 formed in the surface molding layer 4, the holes 9 are preferably arranged differently from the holes of the surface molding layer 4.

(21) The lower resin diffusion layer 8a is formed from a material that undergoes substantially no change in thickness even when pressure is applied inside the cavity during resin impregnation. The lower resin diffusion layer 8a preferably uses a punched metal formed from stainless steel, aluminum, iron or copper or the like. The hole opening rate of the lower resin diffusion layer 8a is typically from approximately 10% to 60%, as such materials are readily available, but innovations such as making the shape of the holes rectangular enable even higher hole opening rates to be achieved. The thickness of the punched metal is preferably from approximately 1 mm to 4 mm.

(22) The upper resin diffusion layer 8b is stacked on top of the lower resin diffusion layer 8a. In FIG. 1, the upper resin diffusion layer 8b is disposed so that one surface (the upper surface) contacts the upper mold, enabling resin to be injected directly into the upper resin diffusion layer 8b from the resin supply line. A plurality of holes 10 that pass through the layer in the thickness direction are formed in the upper resin diffusion layer 8b. The hole diameter of the holes 10 is set to a larger diameter than the holes 9 formed in the lower resin diffusion layer 8a. The hole opening rate of the upper resin diffusion layer 8b is higher than the hole opening rate of the lower resin diffusion layer 8a. The shape of the holes 10 may be circular, oval, square, hexagonal or rectangular or the like, and is preferably selected so that the shape of the holes 10 differs from the shape of the holes 9 formed in the lower resin diffusion layer 8a. The arrangement of the holes 10 may be a staggered array or a lattice arrangement or the like, and may be selected as appropriate, but in order to ensure a phase difference relative to the holes 9 formed in the lower resin diffusion layer 8a, the holes 10 are preferably arranged differently from the holes of the lower resin diffusion layer 8a.

(23) The upper resin diffusion layer 8b is formed from a material that undergoes substantially no change in thickness even when pressure is applied inside the cavity during resin impregnation. The upper resin diffusion layer 8b preferably uses a punched metal formed from stainless steel, aluminum, iron or copper or the like. The thickness of the upper resin diffusion layer 8b is preferably from approximately 1 mm to 4 mm.

(24) FIG. 2 to FIG. 4 are examples of the punched metal used for the surface molding layer 4 or the resin diffusion layer 8. As illustrated in FIG. 2 to FIG. 4, the punched metal has not been trimmed.

(25) In the surface molding layer 4 and the resin diffusion layer 8 having the configurations described above, the holes 7, 9 and 10 formed in each of the layers overlap and are connected to the holes 7, 9 and 10 formed in the other layers, thus forming a resin flow path through which the resin can flow in the thickness direction and the in-plane direction.

(26) Next is a description of the RTM molding method according to the present embodiment.

(27) The reinforcing fiber used in the present embodiment is carbon fiber, glass fiber, aramid fiber, metal fiber, boron fiber, alumina fiber, or silicon carbide high-strength synthetic fiber or the like. Carbon fiber is particularly desirable. There are no particular limitations on the form of the fiber-reinforced base material 11, and a unidirectional sheet or woven fabric or the like can be employed. A plurality of layers of such a material are typically stacked to form the base material, and if necessary, a semi-molded body that has been shaped in advance may be used. In this case, the semi-molded body may be prepared by performing shape formation with the fiber-reinforced base material 11 positioned on top of a rigid porous member formed from the surface molding layer 4 and the resin diffusion layer 8. Further, a semi-molded body may also be formed by performing shape formation with the fiber-reinforced base material 11 sandwiched between two rigid porous members. The resulting semi-molded body may then be supplied to the RTM molding device 100.

(28) In the present embodiment, a resin injection molding (RIM) monomer or the like that forms a thermosetting resin or thermoplastic resin is typically used as the resin. Examples of the thermosetting resin include epoxy resins, unsaturated polyester resins, polyvinyl ester resins, phenolic resins, guanamine resins, polyimide resins such as bismaleimide-triazine resins, furan resins, polyurethane resins, poly(diallyl phthalate) resins, melamine resins, urea resins and amino resins.

(29) Further, resins prepared by blending a plurality of materials selected from among thermosetting resins, thermoplastic resins and rubbers can also be used.

(30) In the RTM molding method according to the present embodiment, first, the fiber-reinforced base material 11 is placed inside the cavity of the lower die. The surface molding layer 4, the lower resin diffusion layer 8a and the upper resin diffusion layer 8b are then stacked sequentially on top of the fiber-reinforced base material 11. At this time, the holes 7, 9 and 10 within each of the adjacent layers interconnect to form a resin flow path. Subsequently, the upper mold is fastened to the lower mold. A release cloth (peel ply) may be inserted between the fiber-reinforced base material 11 and surface molding layer 4. Next, suction is applied from the suction line 3, and the inside of the cavity is placed under reduced pressure. The resin is then injected under pressure through the resin injection line 2 and into the upper resin diffusion layer 8b inside the cavity.

(31) The injected resin passes through the resin flow path and diffuses in both the in-plane direction and the thickness direction. FIG. 5 is a cross-sectional view explaining the flow of resin. For the sake of simplicity, the resin diffusion layer 8 is illustrated as a single layer. In FIG. 5, the resin flow threads its way through the holes formed in the upper and lower layers (the resin diffusion layer 8 and the surface molding layer 4). Because the sizes of the holes formed in the upper and lower layers differ, any hole formed in one layer may be connected to two or more holes formed in another layer. Even in the case where, within a single cross-section, a hole A and a hole B.sub.1 in vertically adjacent layers are not interconnected, the hole A will be connected with a hole B.sub.2 (not shown in the figure) within another cross-section (for example, in the depth direction of FIG. 5), and therefore the resin can still flow along the in-plane direction via the hole B.sub.2. If layers having holes of different shapes are positioned adjacent to one another, then a more reliable resin flow path can be formed. Furthermore, if layers that have been perforated with different hole arrangements are positioned adjacent to one another, then a more reliable resin flow path can be formed.

(32) The resin that has diffused through the resin flow path is supplied from the holes 7 formed in the surface molding layer 4 to substantially the entire surface of the fiber-reinforced base material 11, and penetrates through the fiber-reinforced base material 11 in the thickness direction. At this time, surplus resin is discharged from the suction line 3. Once the entire fiber-reinforced base material 11 has been impregnated with the resin, suction is stopped. Subsequently, the inside of the cavity is held at or above a predetermined pressure (for example, one atmosphere (101,325 Pa)), and the resin is cured. In those cases where a punched metal is used as the surface molding layer 4 and the resin diffusion layer 8, the punched metal may be discarded following release of the molded body. This simplifies cleaning of the molding dies following mold release.

(33) When the present embodiment was used to mold a flat plate-shaped structural member having dimensions of 180 mm150 mmplate thickness 25 mm, the fiber-reinforced base material was able to be impregnated with the resin in approximately 10 minutes. When the same flat plate-shaped structural member was molded using a conventional method in which resin impregnation was performed from one end of the fiber-reinforced base material, such as the method shown in FIG. 9, approximately 35 minutes were required to impregnate the fiber-reinforced base material with resin. On the basis of these results it was evident that the present embodiment enables the fiber-reinforced base material resin to be impregnated with resin in a short period of time.

Second Embodiment

(34) In this embodiment, the shape of the molded body is a C-shape. One example of a C-shaped structural member is illustrated in FIG. 6. FIG. 6(a) is a top view, and FIG. 6(b) is a cross-sectional view. In FIG. 6, the size of the C-shaped structural member is 300 mm180 mmplate thickness 40 mm, and the size of the concave recess is 100 mm100 mm.

(35) FIG. 7 illustrates a cross-sectional view of an RTM molding device 200 used for molding the C-shaped structural member illustrated in FIG. 6. In a similar manner to the first embodiment, the RTM molding device 200 comprises a molding die 21, a resin injection line 22, a suction line 23, a surface molding layer 24 and a resin diffusion portion.

(36) The molding die 21 is composed of an upper die and a lower die. Joining the upper die to the lower die forms an internal cavity. A sealing member 26 is provided at the interface between the upper die and the lower die so that when the upper die and the lower die are joined together, the inside of the cavity is tightly sealed.

(37) The resin injection line 22 and the suction line 23 are provided in connection with the inside of the cavity. In FIG. 7, one end of the resin injection line 22 is positioned at one end face of the inside of the C-shaped cavity, and one end of the suction line 23 is positioned at the other end face of the inside of the C-shaped cavity.

(38) The surface molding layer 24 is the same as that of the first embodiment.

(39) The resin diffusion portion is composed of a single resin diffusion layer 28, and a channel (not shown in the figure) which is formed in the surface of the molding die that contacts the resin diffusion layer 28. In some cases, the resin diffusion layer 28 may be omitted.

(40) The resin diffusion layer 28 is the same as the upper resin diffusion layer 8b of the first embodiment. In this embodiment, because the shape of the molded body that is formed is a C-shape, the thickness of the resin diffusion layer (punched metal) 28 is preferably from 1 mm to 4 mm. This enables the layer to conform to the R value.

(41) The channel formed in the molding die is a linear channel that connects to the resin injection line 22. The linear channel is preferably V-shaped (triangular). This facilitates cleaning following mold release. The location for the formation of the linear channel may be determined as appropriate.

(42) Next is a description of the RTM molding method according to the present embodiment. A fiber-reinforced base material 31 is placed inside the cavity, and the surface molding layer 24 and the resin diffusion layer 28 are then stacked sequentially on top of the base material. At this time, the channel formed in the molding die connects with the holes formed in the resin diffusion layer 28, and the holes in the surface molding layer 24 connect with the holes in the resin diffusion layer 28, thus forming a resin flow path. A release cloth (peel ply) may be inserted between the fiber-reinforced base material 31 and surface molding layer 24. Suction is applied from the suction line 23 to reduce the pressure inside the cavity, and the resin is injected under pressure through the resin injection line 22.

(43) The resin injected under pressure into the cavity from the resin injection line 22 enters the resin diffusion layer 28, and also passes through the linear channel and diffuses in an in-plane direction through the resin diffusion layer 28 that contacts the molding die 21. As a result, the resin can diffuse rapidly into the surface molding layer 24 even when only a single resin diffusion layer 28 is provided.

(44) The resin passes through the resin flow path, and diffuses in both the in-plane direction and the thickness direction. The resin is supplied from the plurality of holes formed in the surface molding layer 24 to substantially the entire surface of the fiber-reinforced base material 31, and penetrates through the fiber-reinforced base material 31 in the thickness direction. At this time, surplus resin is discharged from the suction line 23. Once the entire fiber-reinforced base material 31 has been impregnated with the resin, suction is stopped. Subsequently, the inside of the cavity is held at a predetermined pressure, and the resin is cured to form a molded body.

(45) In the first embodiment and the second embodiment, by providing the surface molding layer and the resin diffusion portion, the resin that is injected under pressure into the inside of the cavity diffuses, and can be supplied across substantially the entire surface of the fiber-reinforced base material. Further, because the resin flows through the fiber-reinforced base material in the thickness direction, the distance that the resin passes through the fiber-reinforced base material is shorter than the distance in a conventional method (FIG. 8). As a result, even when a high-viscosity resin is used, the fiber-reinforced base material can be impregnated with the resin without causing fiber wrinkle or the like. Further, even if the thickness of the molded body is approximately 40 mm, the fiber-reinforced base material can be impregnated with the resin in a short period of time, without leaving any non-impregnated regions. During molding, the surface molding layer is pressed against the fiber-reinforced base material, but by reducing the size of the holes formed in the surface molding layer, the shape of the holes in the surface molding layer can be prevented from transferring to the surface of the molded body. The surface molding layer and the resin diffusion layer have sufficient rigidity that they no not deform under the pressure inside the cavity during molding. As a result, even when the surface molding layer and the resin diffusion layer are interposed between the molding die and the fiber-reinforced base material, a molded body having high dimensional (thickness) precision can be obtained.

(46) In the first embodiment and the second embodiment, the surface molding layer and the resin diffusion portion were provided on the resin injection side of the fiber-reinforced base material, but there are no particular limitations on the locations for the surface molding layer and the resin diffusion portion. The surface molding layer and the resin diffusion portion may also be provided on the resin discharge side of the fiber-reinforced base material, or may be provided on both the resin injection side and the resin discharge side.

(47) According to the RTM molding device of the structure described above, by adjusting the number of resin diffusion layers and the thickness of those layers, the same molding die can be used to mold molded bodies of different thicknesses. In other words, a minor change in the thickness does not require preparation of a new molding die. Further, a semi-molded body prepared by subjecting a rigid porous member and a fiber-reinforced base material to shape formation can also be used. This type of semi-molded body can prevent damage and deformation during transport.

EXPLANATION OF REFERENCE

(48) 1, 21: Molding die 2, 22: Resin injection line 3, 23: Suction line 4, 24: Surface molding layer 5: Resin diffusion portion 6, 26: Sealing member 7, 9, 10: Hole 8, 8a, 8b: Resin diffusion layer 11,31: Fiber-reinforced base material 40: Intermediate member 41: Porous plate 100, 200: RTM molding device