JP2004306398A - Method for manufacturing frp structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the molding quality of an FRP structure using a preform obtained by surrounding a foaming core material by reinforcing fibers. <P>SOLUTION: The preform 11 is obtained by surrounding a foaming core 2, which is formed by holding reinforcing fibers 9 between two core material pieces 2a and 2b. Non-foamed sheets 7 are preliminarily embedded in the surface layers of the respective core material pieces 2a and 2b. The preform 11 is put in a heated mold 12 and, after the mold is clamped, the mold is filled with a thermosetting resin material as a matrix resin so as to impregnate reinforcing fibers 9 and 10 with the resin material to mold the FRP structure 1 wherein the reinforcing fibers 9 become ribs 4 and the reinforcing fibers become a skin layer 3. The reinforcing fibers 10 are pressed to the mold surface of the mold by the expansion of the non-foamed sheet 7 to prevent molding failure such as the occurrence of wrinkles, uneven wall thickness and the like. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of manufacturing a typical FRP (fiber reinforced plastics) structure as a structure of a composite material, and particularly to a method of forming a foam core material and a skin layer made of fiber reinforced resin surrounding the foam core material. The present invention relates to a method for producing an FRP structure having a rib formed integrally with a skin layer and crossing the foam core inside the foam core.
[0002]
[Prior art]
When manufacturing a three-dimensional FRP structure with a hollow shape, in addition to the construction method using a balloon-shaped hollow bag as a core material, a half-shaped preform is formed as a so-called middle structure. After that, a method of adhesively bonding the preforms to each other is often used.
[0003]
However, in the former method, it is difficult to position and maintain the shape of ribs when it is desired to set partition ribs inside to increase the rigidity and strength of the structure.In the latter method, the bonding process is difficult. The third method is to increase the density of the hollow part by increasing the time required for the production, as well as greatly reducing the productivity for securing the alignment accuracy between the preforms. A method of covering the periphery with a fiber reinforced resin as a small foam material has been attempted, for example, in Patent Documents 1 and 2.
[0004]
According to this method, the foam material is used as the core material (core), the core material is divided at a portion corresponding to the rib, and the reinforcing fiber is sandwiched between the divided core materials, so that good accuracy can be obtained. The ribs can be integrally formed, and a product having an excellent outer surface can be obtained by placing the intermediate molded body in a molding die and molding.
[0005]
[Patent Document 1]
JP-A-11-254566 (FIG. 2)
[0006]
[Patent Document 2]
JP-A-2000-233364 (page 3 and FIG. 4)
[0007]
[Problems to be solved by the invention]
However, foams have a special property of having bubbles throughout, so that when subjected to an external load, the surface is easily dented or depressed, and the density of the foam material is particularly reduced in order to form a lighter product. The smaller the size is, the more remarkable the above tendency becomes.
[0008]
Therefore, when covering the foamed core material with the reinforcing fiber or setting the foamed core material covered with the reinforcing fiber in the molding die, if the foamed core material is depressed or depressed, a large amount of resin is impregnated. In addition to this, the thickness of the product locally increases and the strength is reduced. In addition, when the reinforcing fibers become too weak, wrinkles are generated on the product surface.
[0009]
It is also possible to use a foam material which is hard against external loads and does not easily cause dents or depressions on the surface, but such type of foam material is very expensive, and it is particularly desirable to manufacture an inexpensive and lightweight product. Cannot be adopted in the case.
[0010]
The present invention has been made in view of such problems, and in particular, a rib that is integrated with a skin layer and crosses the foam core material inside a foam core material surrounded by a skin layer made of a fiber-reinforced resin. It is an object of the present invention to provide a method capable of molding a good quality product by using an inexpensive foamed core material on the premise of an FRP structure in which is formed.
[0011]
[Means for Solving the Problems]
As described above, the invention according to claim 1 has a foamed core material and a skin layer made of a fiber-reinforced resin surrounding the foamed core material, and the inside of the foamed core material has It is assumed that the method is a method of manufacturing an FRP structure in which ribs are formed integrally with the skin layer and cross the foamed core material. Then, a step of embedding an unfoamed foam material in the surface layer portion of the foam core material divided into at least two parts, and surrounding the entire foam core material with the reinforcement fibers after sandwiching the reinforcing fibers between the foam core materials. And forming a preform, placing the preform in a molding die, clamping and heating to expand an unfoamed foamed material, and after the heating or in parallel with the heat treatment, in the molding die. And forming a skin layer into a predetermined shape while impregnating the reinforcing fibers with a matrix resin.
[0012]
In this case, the time for heating and the time for filling the matrix resin are exchanged, and as described in claim 2, after the preform is placed in the mold and clamped, first, the matrix resin is filled in the mold. Then, the reinforcing fibers may be impregnated, and then heated to cure the matrix resin impregnated in the reinforcing fibers and foam the unfoamed foam while forming the skin layer into a predetermined shape.
[0013]
In order to further enhance the surface quality of the structure, a concave portion for receiving an unfoamed foam material is formed in advance on the surface layer of the foamed core material, and the concave portion is formed in the concave portion. After arranging an unfoamed sheet-like foam material, or as described in claim 4, after arranging an unfoamed sheet-like foam material in the concave portion, a cover made of the same material as the foam core material is used. It is desirable to coat so as to be flush with the surface of the foamed core material.
[0014]
Therefore, according to the first aspect of the present invention, since the unfoamed foamed material is foamed only after the preform is placed in the molding die and clamped, the reinforcing fibers covering the foamed core material are moved to the outside, ie, outside. The effect of pressing against the mold is exhibited. This makes it possible to prevent the occurrence of wrinkles and variations in wall thickness of the reinforcing fibers and thus the skin layer.
[0015]
【The invention's effect】
According to the invention as set forth in claim 1, since the outer reinforcing fibers are pressed against the mold by foaming of the unfoamed foam material, the thickness of the skin layer containing the reinforcing fibers does not vary, The thickness accuracy can be improved, and a structure that is stable in terms of strength can be formed, and wrinkles of the reinforcing fibers can be prevented, so that the surface quality is also improved. Further, the use of an inexpensive and lightweight foam core material is sufficient due to the quality improvement as described above, so that there is an advantage that a lightweight structure with little increase in cost can be easily formed.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 3 are diagrams showing a preferred embodiment of the present invention. In particular, FIG. 1 shows a schematic structure of a molded FRP structure, and FIG. 2 shows a foamed core material (foamed core) to be the FRP structure 1. ) And an unexpanded foam material are shown in exploded perspective views.
[0017]
The overall shape of the FRP structure 1 shown in FIG. 1 is a substantially solid prismatic or rectangular parallelepiped, and a skin layer (a foam layer 2 made of a thermosetting fiber reinforced resin on the entire six surfaces of which is a core material). A single partition-like rib 4 is formed in the center of the interior and crosses the foam core 2 while being integrated with the skin layer 3. Due to the ribs 4, the foamed core 2 is substantially divided into two right and left parts 2a and 2b. Here, the entire core covered with the skin layer 3 is referred to as a foamed core 2, and each of the right and left cores having the same shape divided into two by the presence of the ribs 4 is referred to as core pieces 2 a and 2 b.
[0018]
As shown in FIG. 2, each of the core pieces 2a and 2b is made of, for example, a hard polyurethane foam, and has a rectangular receiving concave portion 5 as a concave portion on each surface layer of the six outer peripheral surfaces. And a rectangular opening 6 having a stepped portion 6 slightly larger than the receiving recess 5 is also formed. As the above-mentioned rigid polyurethane foam, for example, a lightweight polyurethane having a small density such as a rigid urethane foam “Sofran-RW-30” manufactured by Toyo Tire & Rubber Co., Ltd. is preferable. Further, the receiving recess 5 and the opening 6 are not necessarily provided on the entire six surfaces, but may be set only on the surfaces necessary for product functions.
[0019]
A rectangular unfoamed sheet 7 is arranged in each receiving recess 5 as an unfoamed foam material, and the same material (hard polyurethane foam) as each of the core element pieces 2a and 2b is disposed thereon. A cover sheet 8 having the same rectangular shape as a cover is attached to the opening 6 so as to be flush with the outer peripheral surfaces of the core pieces 2a and 2b, thereby concealing the unfoamed sheet 7 and thereby substantially unfoamed. The sheet 7 is embedded in each of the core pieces 2a and 2b. As the non-foamed sheet 7, for example, a foam adhesive “REDUX206NA” manufactured by Hexcel is used. However, the adhesive is not necessarily required as long as it is a sheet.
[0020]
Therefore, the receiving recess 5 is set to a size capable of receiving the unfoamed sheet 7, and the opening 6 is set to a size capable of receiving the cover sheet 8. In FIG. 2, an unfoamed sheet 7 and a cover sheet 8 which are to be attached to only one specific surface out of the six surfaces of each of the core element pieces 2a and 2b are shown, and the unfoamed sheets 7 The sheet 7 and the cover sheet 8 are not shown.
[0021]
In addition, between the pair of core pieces 2a and 2b, reinforcing fibers having the same size as the surface of the maximum area of the core pieces 2a and 2b (corresponding to the rib 4 in FIG. 9) are sandwiched.
[0022]
In molding the FRP structure 1 shown in FIG. 1, as described above, the unfoamed sheet 7 is placed in each of the receiving recesses 5 for the pair of core pieces 2a and 2b, and the cover sheet is placed in the opening 6. Fit 8 and cover. Thereby, the non-foamed sheet 7 is substantially embedded in the surface layer of each of the core pieces 2a and 2b.
[0023]
Next, the reinforcing fibers 9 are sandwiched between the core pieces 2a and 2b so that the core pieces 2a and 2b are combined to form the foamed core 2. Further, as shown in FIG. 3A, the entire circumference of the foamed core 2 formed by combining the core pieces 2a and 2b with each other is reinforced fiber (a single fiber layer is laminated several times). Cover with. The reinforcing fibers 10 referred to here are to be the skin layers 3 in FIG. 1 and are made of the same material as the reinforcing fibers 9 corresponding to the ribs 4. That is, by covering the foamed core 2 sandwiching the reinforcing fibers 9 to be the ribs 4 with the reinforcing fibers 10 to be the skin layer 3, the FRP structure 1 as shown in FIG. It becomes a reform 11.
[0024]
Here, by merely surrounding the foamed core 2 with the reinforcing fibers 10, it is inevitable that wrinkles Q and gaps G between the single fiber layers are generated on the surface thereof as shown in FIG. do not do.
[0025]
When the preform 11 is obtained in this manner, the preform 11 is placed in the cavity 15 on the lower mold 14 side of the molding die 12 composed of the upper and lower dies (dies) 13 and 14 as shown in FIG. Set and tighten the mold. In this case, before the preform 11 is set, the mold 12 itself is heated in advance and adjusted to a temperature of, for example, about 100 to 120 ° C.
[0026]
When the preform 11 is set in the molding die 12 and clamped, the unfoamed sheet 7 in the preform 11 receives the heat from the molding die 12 and starts foaming. Since the foaming of the sheet 7, which has not been foamed before, involves its volume expansion, the reinforcing fibers 10 on the outer periphery of the core are removed from the inside of the foamed core 2 through the foamed core 2 as shown in FIG. It is pressed against the cavity surface (mold surface) of the molding die 12.
[0027]
Subsequently, a molten resin material of a thermosetting resin such as an epoxy resin is filled as a matrix resin into the cavity 15 through a runner 16 provided in the mold 12, and the reinforcing fibers 9 and the skin layer 3 corresponding to the ribs 4 are filled into the cavity 15. The corresponding reinforcing fibers 10 are impregnated. At this time, since the reinforcing fibers 10 to be the skin layers 3 are pressed against the cavity surface in advance by foaming of the unfoamed sheet 7, the wrinkles Q as shown in FIG. There is no loosening, and no large gap G (see FIG. 3A) is generated between the laminated single fiber layers where the reinforcing fibers 10 are formed.
[0028]
Then, when the filling of the molten resin material of the thermosetting resin is completed, a predetermined pressure-holding state is set to accelerate the curing of the thermosetting resin. With the progress of the curing, as shown in FIG. 3B, the core pieces 2a and 2b having good affinity and the sheet 7 and the cover sheet 8 are integrated, and at the same time, the core pieces 2a and 2b And the reinforcing fibers 9 and 10 are also integrated. In other words, the portion corresponding to the reinforcing fibers 9 impregnated with the molten resin material of the thermosetting resin becomes the rib 4, and the portion corresponding to the reinforcing fibers 10 impregnated with the molten resin material of the thermosetting resin becomes the skin layer 3. Thereafter, after a predetermined time has passed, the mold is removed to obtain the FRP molded product 1 as a product.
[0029]
Here, when filling the molten resin material of the thermosetting resin, the molding die 12 is set at room temperature or at a temperature at which the unfoamed sheet 7 does not foam, and only after the filling of the molten resin material is completed. The temperature of the mold 12 may be increased to a temperature at which the foam sheet 7 foams and the molten resin material hardens. That is, as a characteristic of the molten resin material of the thermosetting resin, the uncured sheet 7 is set to have a property of being cured later than the foaming time.
[0030]
Thus, when the mold 12 is filled with the molten resin material of the thermosetting resin, since the unfoamed sheet 7 is not foamed, the reinforcing fibers 10 to be the skin layer 3 are pressed against the cavity surface. The force is smaller than that of the first embodiment, and as a result, there is a gap between the single fiber layers forming the reinforcing fibers 10, so that the filled molten resin material easily flows through the entire cavity 15, The impregnation into the reinforcing fibers 10 becomes uniform and stable.
[0031]
For this reason, it is possible to form the reinforcing fiber 10 with good impregnating property of the molten resin material. In particular, it is possible to prevent the occurrence of molding defects such as uneven thickness due to the variation in impregnating property. Also, it is possible to form an FRP structure that has been difficult to mold due to poor impregnation.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a schematic structure as an example of an FRP structure.
FIG. 2 is an exploded perspective view showing a mutual relationship with a core element, an unfoamed sheet, and the like that form the FRP structure of FIG. 1;
3A is a cross-sectional view showing a relationship between a preform formed using the elements shown in FIG. 2 and a molding die, and FIG. 3B is a cross-sectional view showing a state in which molding of an FRP structure has been completed.
[Explanation of symbols]
1: FRP structure 2: Foam core (foam core material)
2a, 2b: core element 3: skin layer 4, rib 5, receiving recess (concave portion)
6 Opening 7 Unfoamed sheet (unfoamed foam material)
8. Cover sheet (lid)
9, 10 ... reinforcing fiber 11 ... preform 12 ... molding die

Claims (4)

It has a foam core material and a skin layer made of fiber reinforced resin surrounding the foam core material, and a rib is formed inside the foam core material integrally with the skin layer and crossing the foam core material. A method for manufacturing an FRP structure, comprising:
Embedding an unfoamed foam material in the surface layer of the foam core material divided into at least two parts,
A step of sandwiching the reinforcing fibers between the foamed core materials and surrounding the entire foamed core material with the reinforcing fibers to form a preform;
A step of heating the unfoamed foam material by heating the preform in a mold, clamping the mold and heating,
A step of forming the skin layer into a predetermined shape while filling the matrix resin in the mold and impregnating the reinforcing fibers after the heating or in parallel with the heat treatment,
A method for producing an FRP structure, comprising: It has a foam core material and a skin layer made of fiber reinforced resin surrounding the foam core material, and a rib is formed inside the foam core material integrally with the skin layer and crossing the foam core material. A method of manufacturing an FRP structure, comprising:
Embedding an unfoamed foam material in the surface layer of the foam core material divided into at least two parts,
A step of sandwiching the reinforcing fibers between the foamed core materials and surrounding the entire foamed core material with the reinforcing fibers to form a preform;
A step of placing the preform in a mold and clamping the mold,
A step of filling the mold resin with a matrix resin and impregnating the reinforcing fibers,
Heating after filling the matrix resin, curing the matrix resin impregnated in the reinforcing fibers and foaming the unfoamed foam while forming the skin layer into a predetermined shape,
A method for producing an FRP structure, comprising: A concave portion for receiving an unfoamed foam material is previously formed in a surface layer portion of the foamed core material, and an unfoamed sheet-like foam material is arranged in the concave portion. A manufacturing method of the FRP structure according to the above. 5. An unfoamed sheet-like foam material is arranged in the concave portion, and then covered with a lid made of the same material as the foam core material so as to be flush with the surface of the foam core material. 3. The method for producing an FRP structure according to item 1.

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