JPH07278319A - Production of three-dimensional multiaxial woven fabric composite material - Google Patents

Abstract

PURPOSE:To provide a production method capable of inexpensively molding a three-dimensional multiaxial woven fabric composite material having excellent mechanical properties free from defects, coordinating a use condition. CONSTITUTION:A three-dimensional multiaxial woven fabric preform 8 is packed into a variable volume molding container 5 and an epoxy resin 7 is filled into the molding container 5. The molding container is put in a pressure container 1 charged with a pressure medium 6, is provided with necessary hydrostatic pressure by the pressure medium 6 at a prescribed curing temperature. After the fluidity of the resin 7 is substantially lost, the molding container 5 is taken out from the pressure container 1 and then cured.

Description

Detailed Description of the Invention

[0001] The present invention relates to a method for producing a three-dimensional multiaxial woven fabric composite material using a three-dimensional multiaxial woven fabric preform as a reinforcing base material and a thermosetting resin as a matrix.

[0002]

2. Description of the Related Art In molding a fiber-reinforced composite material using a thermosetting resin as a matrix, the volume shrinkage of the resin due to the curing reaction of the resin during molding and the volume of the cured resin generated in the cooling process after the completion of the curing reaction Due to the shrinkage, residual stress is generated inside the composite material. When the fiber-reinforced composite material is a two-dimensional composite material, for example, a laminated structure, the composite material can shrink in a direction perpendicular to the laminated surface, and therefore relaxation of residual stress is expected. Further, it is possible to reduce the residual stress by pressing in this direction during molding. Therefore, in the molding of the two-dimensional composite material (laminated structure), methods such as press molding and autoclave molding are often used.

On the other hand, in the case of a three-dimensional multi-axial woven composite material, since the three-dimensional restraint by the reinforcing fiber occurs, the above-mentioned residual stress generated during molding is not relaxed, and compared with the case of a two-dimensional composite material. There is a problem that defects are likely to occur in the inside. Furthermore, since it is necessary to form the three-dimensional multiaxial woven fabric preform, which is a reinforced substrate, without causing deformation, a forming method such as press forming or autoclave forming that applies pressure in a specific direction cannot be used. Therefore, in the molding of the three-dimensional multiaxial woven fabric composite material, a molding method such as resin transfer molding is generally used.

According to this method, a three-dimensional multiaxial woven fabric preform is loaded in a mold, and a thermosetting resin is filled in the mold.
After impregnation, it is cured. For example, in molding a composite material of this type, the preform is loaded in a mold, and after filling and impregnating with the resin, 1
A method of curing and molding a resin while applying a pressure of 5.5 MPa has been reported (Proceedings of the 6th Next Generation Industrial Fundamental Technology Symposium, published by Japan Industrial Technology Promotion Association (198).
9) p239).

In this method, a constant pressure is applied throughout the curing process for the purpose of reducing the occurrence of the internal defects, but cracks are generated in the resin pool portion caused by the variation in the weave density of the preform. There is a problem that it is recognized, and in addition, a large backup mechanism for holding the pressure of the mold is required to apply pressure throughout the curing process, which is an obstacle to improvement of productivity.

Further, there has been reported a method for molding a three-dimensional multiaxial woven composite material under hydrostatic pressure while the composite material is immersed in a liquid heating / pressurizing medium (Japanese Patent Laid-Open No. 03- No. 284937), but this method is not suitable for forming a three-dimensional multiaxial woven composite material in which a thermosetting resin is used as a matrix. As described above, in a three-dimensional multiaxial woven fabric composite material using a thermosetting resin as a matrix, there is no manufacturing method capable of reliably manufacturing a defect-free molded article at a low cost, and an extremely large manufacturing as long as the conventional manufacturing method is extended. Needed a cost.

[0007]

The technical problem to be solved by the present invention is to use it in the production of a three-dimensional multiaxial woven fabric composite material using a three-dimensional multiaxial woven fabric preform as a reinforcing base material and a thermosetting resin as a matrix. It is an object of the present invention to provide a manufacturing method capable of inexpensively molding a three-dimensional multiaxial woven fabric composite material that is defect-free and has excellent mechanical properties, which is suitable for temperature conditions.

In addition, in order to deal with the above-mentioned problems of the prior art, the present inventors previously filed Japanese Patent Application No. 06-024716 to substantially eliminate the fluidity of the thermosetting resin during the curing process. The specific volume at the point where the thermosetting resin has a specific volume at the room temperature or lower than the specific volume at the intended use temperature of the composite material lower than room temperature From the stage shown, the fluidity is applied until it disappears substantially, and a method is also proposed in which the pressure is controlled after that.
Three-dimensional with no practical problem, even if the above-mentioned curing reaction progresses and the fluidity is substantially extinguished, the necessary pressure is applied, and after the fluidity disappears, the pressure is removed and post-curing is performed. It has been found that a multiaxial woven composite material can be formed. The present invention is based on such knowledge, and its technical problem is to mold a defect-free three-dimensional multiaxial woven fabric composite material excellent in mechanical properties in accordance with the above-mentioned use conditions with high productivity. It is to provide a manufacturing method.

[0009]

In order to solve the above problems, the method of the present invention is a three-dimensional multiaxial woven fabric using a three-dimensional multiaxial woven fabric preform as a base material and a thermosetting resin as a matrix. In the method for manufacturing a composite material, the specific volume at the point where the fluidity of the thermosetting resin substantially disappears during the curing process of the thermosetting resin is lower than the specific volume at room temperature or the intended temperature of the composite material lower than that. The pressure required to reduce the fluidity is applied at the time when the curing reaction progresses and the fluidity thereof substantially disappears. After the fluidity disappears, the pressure is removed and post-curing is performed. It is a thing.

Further, in the above method, the three-dimensional multiaxial woven fabric preform is loaded into a molding container of variable volume, the thermosetting resin is filled in the molding container, and the pressure medium is filled with a pressure medium. Stored in a container, applying the required hydrostatic pressure by pressurizing the pressure medium under the required curing temperature,
After the fluidity of the thermosetting resin disappears, the molding container can be taken out of the pressure container and post-cured.
Further, in the above method, the three-dimensional multiaxial woven fabric preform is loaded into a pressure-resistant mold, and a thermosetting resin is filled in the mold, and a required pressure is set under a required curing temperature. After being applied to the resin and the fluidity of the thermosetting resin disappeared,
The three-dimensional multiaxial woven fabric preform can be removed from the mold and post-cured.

In the above-mentioned method of the present invention, the three-dimensional multiaxial woven fabric preform used as the reinforcing substrate is woven by arranging fiber bundles of reinforcing fibers such as carbon fibers, metal fibers or ceramic fibers in the multiaxial direction. What was done can be used. Considering the mechanical properties of composite materials,
It is desirable to use carbon fiber as the reinforcing fiber. In addition, if necessary, a reinforced fiber is preliminarily molded into a rod shape using a thermosetting resin, and a three-dimensional multiaxial woven fabric preform is obtained by weaving this unidirectional rod-shaped composite material in a multiaxial direction. It is also possible to use.

On the other hand, as the thermosetting resin used as the matrix in the present invention, any thermosetting resin such as epoxy resin or phenol resin can be used. However, considering the moldability and the physical properties of the composite material, the epoxy resin can be used. It is more preferable to use a resin.

In the present invention, as a method of impregnating the three-dimensional multiaxial woven fabric preform with a thermosetting resin, when the resin is fed by using a pump or the like at atmospheric pressure,
After making the inside of the mold a vacuum state, or after making the preform a vacuum state in advance, or making the entire molding container a vacuum state, it is impregnated with the defoamed resin in advance. It is desirable to improve the condition.
Then, the curing temperature cycle in the case of molding by curing the preform impregnated with the above resin is various methods such as a method of curing and molding at a constant temperature or a method of curing and molding through a plurality of temperature stages. Cycles can be adopted.

In the thermosetting resin of the composite material molded by such a method, internal stress is not acting or internal compressive stress is acting at room temperature or a lower use temperature lower than that. , According to the usage conditions,
It is possible to obtain a three-dimensional multiaxial woven fabric composite material which is defect-free and has excellent mechanical properties. Moreover, there is no practical problem even if a pressure necessary for the fluidity disappears after the curing reaction progresses and the fluid is extinguished to remove the pressure for post-curing. It is based on the knowledge that a three-dimensional multiaxial woven fabric composite material can be formed, and therefore, the above-mentioned three-dimensional multiaxial woven fabric composite material can be formed easily with high productivity.

The method of the present invention will be described in more detail. Defects occurring during molding of a three-dimensional multiaxial woven fabric composite material in which a three-dimensional multiaxial woven fabric preform is used as a reinforcing base material and a thermosetting resin is used as a matrix. Is due to volume change (mainly shrinkage) of the thermosetting resin during molding. In the case of a three-dimensional multiaxial woven composite material, there is a three-dimensional constraint by the reinforcing fibers during molding, so the residual stress P due to shrinkage during molding is
Can be expressed as

P = K × (v _G −v _R ) / v _G (1) where K: bulk modulus of the resin, v _G : the resin substantially flows during the curing process under a certain molding pressure. Specific volume at the point where the composite material shows no property, v _R : normal temperature or a planned temperature under the pressure (generally atmospheric pressure) at which the composite material is actually used (usage temperature when the use temperature of the composite material is equal to or lower than room temperature) ) Is the specific volume in. The reinforcing fibers generally used in the three-dimensional multiaxial woven composite material are carbon fibers,
Since it is a metal fiber or a ceramic fiber, its linear expansion coefficient is smaller than the linear expansion coefficient of resin and can be ignored in the above formula (1).

In this equation (1), [(v _G -v _R ) / v
The term [ _G ] is a term indicating the amount of residual strain during molding. If this term takes a positive value, tensile stress acts on the resin, causing defects in the resin, but if it takes zero or a negative value, no stress acts on the resin. Or, since the stress on the compression side acts, the defect does not occur in the resin. Therefore, in the process of curing the resin, the pressure necessary to reduce the specific volume of the resin at the point where the fluidity of the resin substantially disappears compared to the specific volume of the resin at room temperature or at the intended temperature is applied. By doing so, no defects occur in the composite material.

The value of the specific volume at the point where the fluidity of the resin substantially disappears during the curing process of the resin under a specific pressure can be measured by various methods. For example, a method of measuring a volume change when a resin is enclosed in a pressure vessel of a cylinder having a piston and cured under a specific pressure, or a method of measuring a volume change using a PVT measuring device (Mitani et al., Proceedings of the third Japan inter
national SAMPE symposium, Dec, 7-9, 1993, p 834)
And so on.

The specific volume value obtained under various pressures using such a method is used as a reference specific volume, that is, the specific volume of the resin at room temperature or at the intended temperature (referred to as reference specific volume).
By comparing with, it is possible to obtain a pressure that does not cause the above defects. Also, the specific volume change behavior and compression rate change behavior of the resin during the curing process should be obtained in advance, and the pressure required for the specific volume of the resin to become smaller than the reference specific volume during the curing process should be estimated. Is also possible. The specific volume change behavior and compression rate change behavior of the resin during the curing process are
It can be measured using a measuring device.

The inventors of the present invention have studied the necessary pressure to be applied to the resin in the curing process with respect to the value of the reference specific volume, and as a result, the pressure required to compress the resin is It has been found that in the initial stage of the process, that is, until the liquid resin loses fluidity, it monotonically decreases. Therefore, the pressure required to equalize the specific volume at the point where the fluidity of the resin substantially disappears during the curing process to the above-mentioned reference pressure is the resin at the stage where the resin is still fluid. The pressure is lower than the pressure required to compress to the reference specific volume and is insufficient to compress the resin in the fluidity stage to the reference specific volume.

However, when the resin is still fluid, even if the pressure applied to the resin is insufficient to compress it to the above-mentioned reference specific volume, its fluidity during the curing process. Is the pressure necessary for the specific volume at the point of disappearing to be smaller than the reference specific volume,
If it is applied at the time when the above-mentioned curing reaction proceeds and its fluidity substantially disappears, no defects will occur in the molded composite material. This is because the curing shrinkage is supplemented by the flow of the resin.

In addition, after the fluidity of the resin has substantially disappeared, the specific volume of the resin may change, and the pressure necessary to obtain the value of the reference specific volume may change. However, even if this change requires an increase in the pressure required to reach the value of the above-mentioned reference specific volume, the specific volume at the point where the fluidity thereof substantially disappears is If the pressure required to become smaller than the specific volume is applied at the time when the fluidity thereof substantially disappears, even if such a specific volume change of the resin occurs, the molded composite The material is free of defects.

Further, in molding the thermosetting resin,
The resin may cure via multiple temperature steps.
That is, for example, the resin is cured at a relatively low temperature until the fluidity disappears, and then the temperature is further raised to perform the post-curing. In this case, when curing proceeds until the fluidity of the resin substantially disappears at a relatively low temperature in the initial stage, the specific volume of the resin at the point where the fluidity substantially disappears in the curing process, By applying the pressure required to become smaller than the specific volume at the normal temperature or the planned use temperature, whichever is lower, at the time when the fluidity thereof substantially disappears, a composite without residual strain and defects is obtained. The material can be molded.

In the post-curing of the resin whose flowability has substantially disappeared, it is considered that the resin exhibits thermal expansion as the temperature rises again in the post-curing treatment, but after the fluidity disappears. In the three-dimensional multi-axial woven composite material, the molded composite material itself has a structure that can withstand the stress generated inside, and cancels the tensile stress due to the thermal expansion inside the composite material. In (1), defects are not generated in the molded composite material without applying a pressure corresponding to the thermal expansion of the resin.

Based on these findings, the specific volume at the point where the fluidity of the thermosetting resin substantially disappears during the curing process, the specific volume of the composite material is either room temperature or the intended use temperature, whichever is lower. If the pressure required to become smaller than the specific volume is applied at the time when the above-mentioned curing reaction progresses and its fluidity disappears substantially, it is possible to reduce the cost of a composite material that is defect-free and has excellent mechanical properties. It can be molded and after its fluidity disappears,
By transferring the molded composite material to a pressure vessel that does not require pressure resistance, a mold or the like can be used efficiently, and the number of moldings of this composite material per hour can be increased.

The method of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an apparatus for producing a three-dimensional multiaxial woven composite material for carrying out the method of the present invention. This apparatus includes a pressure container 1, a heater 2 for heating the pressure container 1, a temperature control device 3 for controlling the heater 2, a pressure control device 4 for controlling a molding pressure, and a molding container housed in the pressure container 1. 5 and.

The pressure vessel 1 is common to the molding of composite materials of various shapes. A heater 2 is provided around the outer circumference of the pressure vessel 1.
The heating temperature of the heater 2 is controlled by the temperature control device 3, and the composite material is cured and molded under the curing temperature cycle described later. In order to confirm the temperature in this curing temperature cycle, a thermometer is attached to the pressure vessel 1, and a pressure gauge for pressure control is attached. A molding container 5 is housed inside the pressure container 1, and the periphery of the molding container 5 is filled with a pressure medium 6 whose pressure is controlled by the pressure control device 4.

The molding container 5 into which the three-dimensional multiaxial woven fabric preform 8 is loaded has a variable volume which forms a cylinder structure having a piston 5a, and when the pressure medium 6 presses the piston 5a, the molding container 5 is formed. Hydrostatic pressure can be applied to the epoxy resin 7 in 5. The preform 8 is loaded inside the molding container 5 and the defoamed resin 7 is filled in advance, so that the preform 8 is completely impregnated with the resin 7.

The molding container 5 to be used is subjected to hydrostatic pressure in the pressure container 1, but the resin 7 filled in the molding container 5 is used.
Since it is balanced with the pressure of 1., it does not necessarily have to have a structure that can withstand the pressure at the time of molding, has sufficient strength to hold the shape of the preform 8, and does not deform the container when the resin 7 is filled. It only needs to have strength. However, it is necessary to have a structure that does not hinder the volume change of the resin 7 during molding.

Various examples of the structure of the molding container 5, including those shown in FIG. 2, are conceivable, but any structure and material may be used as long as there is no problem in molding. The figure (a) is an example of a bellows structure in which the piston 5a is replaced with a bellows 5b, and the figure (b) uses a rubber-like film 5c to close the container mouth portion and change the volume of the resin 7. (C) and (d) of the structure that is deformed according to
The structure is open to the pressure medium 6 used when and may be in direct contact with each other. A porous sheet 5d is formed in the same figure (c), and a small hole 5e is formed in the same figure (d). ing.

In addition to these structures, for example, a molded container is a thin container that is easily deformable, a container using a material having low rigidity such as plastic is used, and the entire container is deformed, In order to easily maintain the shape of the preform 8 in a thin container, a material that can withstand the molding conditions is suitable as the material of the container, but the open type container in which the resin 7 can be easily moved is installed. A thing can also be used. It is also possible to use a container having a structure in which the container can be divided so that the molded product can be easily taken out. Furthermore,
As the material of the container, one that can withstand under molding conditions is suitable, but if it can withstand the point that the resin 7 does not substantially show, it may be one that can be subsequently broken.

When the three-dimensional multiaxial woven composite material is manufactured by the manufacturing apparatus having the above-mentioned structure, the preform 8 is loaded into the molding container 5, the resin 7 is filled and impregnated, and the molding container 5 is further packed. Place in pressure vessel 1.
As a method for impregnating the preform 8, the resin 7 is sent in the air using a pump or the like.
It is effective to place the preform 8 in a vacuum atmosphere in advance by an appropriate means, such as storing the entire molding container 5 accommodating the above in a vacuum container and sending the liquid. Furthermore, the preform 8 is placed in a vacuum state in advance and impregnated with the resin 7 that has been defoamed beforehand.
It is desirable in terms of improving the molding condition. At the time of impregnation with the resin 7, it is necessary to add an extra amount to the molding container 5 by the amount of the volume reduction of the resin 7 upon curing.

After the resin 7 is impregnated, the molding container 5 is placed in the pressure container 1 and the pressure medium 6 is sealed therein, and then molding is carried out under a predetermined temperature and pressure condition. Where the pressure medium 6
As a liquid, such as silicone oil, at the required temperature,
Those that are stable under pressure are preferred. The pressure required at the time of molding is transmitted from the pressure medium 6 to the resin 7 in the molding container 5 via the piston 5a.

At the time of molding, the specific volume at the point where the fluidity of the resin 7 substantially disappears during the curing process is smaller than the specific volume after the completion of curing at the normal temperature or the intended temperature, whichever is lower. The pressure necessary to achieve this may be applied when the fluidity of the resin substantially disappears. After that, the molding container 5 is taken out from the pressure container 1 and post-cured at atmospheric pressure.

The apparatus for producing a three-dimensional multiaxial woven composite material may be a conventional die. Figure 3
Shows schematically a manufacturing apparatus using the mold. When manufacturing composite materials with this equipment,
The mold 10 is loaded with the preform 8, and the resin 7 defoamed in advance is supplied from the resin tank 12 through the valves 13 and 14 by the resin pressurizing device 11 so as to fill and impregnate the mold 10. In this case, the inside of the mold 10 is vacuumed by the vacuum device 15 as needed. Valve 1 after impregnation
6 is closed, heating is performed by the heater 17 provided around the mold 10, and curing and molding are performed while applying a required pressure by the pressurizing device 11.

At the stage where the resin 7 is still fluid at the initial stage of curing, the resin has the above-mentioned pressure in the mold, but as described above, the above-mentioned pressure is applied throughout the curing process. The specific volume at the point where the fluidity of the resin 7 practically disappears in this curing process is smaller than the specific volume after the completion of curing at the lower temperature of the room temperature or the intended temperature. The pressure necessary to achieve this may be applied when the fluidity of the resin substantially disappears. After the fluidity of the resin 7 has substantially disappeared, the molded body is taken out of the mold and post-cured at atmospheric pressure. In this case, the mold 10
And its backup mechanism, resin 7 during the curing process
The material and structure need to withstand the temperature and pressure at the time when the fluidity of the is substantially eliminated, but it is not necessarily required to withstand the temperature and pressure in the post-curing process.

[0037]

EXAMPLES Examples of the manufacturing method according to the present invention will be shown below. As the epoxy resin 7 for the matrix, a mixture of Epicoat 828 (manufactured by Yuka Shell Co., Ltd.) as a main agent and Ethacure 100 (manufactured by Ethyl Corp.) as a curing agent at a weight ratio of 100: 24 was used after defoaming. Was cured under atmospheric pressure. The curing temperature cycle was as follows. That is,
The temperature is raised from 40 ° C to 80 ° C over 40 minutes, and at 1 ° C at 1 ° C
After holding for 5 hours, raise the temperature to 180 ° C over 80 minutes,
After holding at 180 ° C. for 4 hours, it was cooled to room temperature (about 20 ° C.) for about 12 hours. Resin 7 after curing in this case
Had a specific volume of 0.860 cm ³ / g at 20 ° C.

Next, the specific volume and compressibility of the epoxy resin 7 during the curing process were measured using the PVT measuring device. The curing temperature cycle in this case was the same as the above cycle. The specific volume was determined by measuring the value under pressure of 100 kgf / cm ² . The compressibility was as shown in FIG. 4 as a result of the change in the specific volume when the pressure was changed by ± 40 kgf / cm ² . Then, the specific volume of the resin 7 is 0.860 from the specific volume and the compression rate.
Figure 5 shows the results of calculating the pressure required to achieve cm ³ / g.
Shown in.

As shown in FIG. 4, the specific volume of the resin 7 monotonously decreased during the curing process at 80 ° C. for 15 hours and converged to a substantially constant value after 15 hours, and the compression rate was in the initial stage. It can be seen that it decreases monotonically during the curing process for 8 hours, and decreases rapidly after the lapse of 8 hours. The change after the lapse of 8 hours indicates that the resin 7 is vitrified from this point and loses its fluidity. The vitrification point of the resin 7 obtained from such a change in compressibility is
When the temperature was held at 80 ° C., it was 9 hours after the start of holding. When the pressure required to bring the specific volume to 0.860 cm ³ / g after 9 hours have elapsed from the start of this holding is determined from FIG. 5, the pressure is 350 kgf / cm ² .

As a result of investigating the fluidity of the epoxy resin in the curing process, it was confirmed that the fluidity was maintained at 80 ° C. and 8 hours after the initiation of the retention. The pressure required to reach a specific volume of 0.860 cm ³ / g after 8 hours from the start of the holding is 400 kgf / cm ^{2 as} determined from the above-mentioned FIG. 5, which is the same as the pressure determined from the vitrification point. It becomes almost the same value. Therefore, it can be estimated that the pressure required to mold a defect-free three-dimensional composite material is at least 400 kgf / cm ² .

Further, in FIG. 5, the pressure required to bring the specific volume of the resin 7 to 0.860 cm ³ / g in the post-curing process at 180 ° C. is about 1000 kgf / cm ² , and This specific volume was 0.86 in the initial stage.
The pressure required to reach 0 cm ³ / g is about 14
Although it is shown to be 00 kgf / cm ² , as described above, the specific volume at the point where the fluidity of the resin 7 substantially disappears during the curing process, whichever is lower than the room temperature or the scheduled temperature for use. The pressure required to become smaller than the specific volume after completion of curing at temperature, that is, 400 kgf / cm ² ,
If it is given when the fluidity of the resin 7 substantially disappears,
It is possible to obtain a defect-free three-dimensional composite material without applying the above high pressure.

Next, at the time when the fluidity of the resin 7 substantially disappears, the occurrence of defects in the three-dimensional composite material formed by applying a pressure of 400 kgf / cm ² is examined.
/ Cm < ² > was given and it investigated in comparison with what was shape | molded. This has a cross section of 0.81 mm square and a fiber content of 7
A rod-type three-dimensional triaxial woven fabric preform 8 was prepared using a carbon fiber reinforced rod-shaped unidirectional composite material in which 0% epoxy resin 7 was used as a matrix (X and Y axis directions: 9).
This sample was created by combining 18 x 18, Z axis direction: 10 x 10, and the sample size is about 16 x 16 x
It is 30 mm. ).

The preform 8 was put into a polypropylene container (commercial photographic film container) having an inner diameter of 30 mm and a height of 45 mm as the molding container 5, and the defoamed epoxy resin 7 was used to fill and impregnate the air bubbles. Be careful not to cover it with a lid. The main molding container 5 is easily deformed when an external pressure is applied. After that, the molding container 5 was put into the pressure container 1, and silicone oil was used as the pressure medium 6 and cured and molded under a predetermined pressure. The curing temperature cycle used for this was the same as the above temperature cycle.

The pressure applied to this is 40 ° C. above.
To 80 ° C. and the atmospheric pressure is maintained until the temperature is maintained at 80 ° C. for 8 hours, and after 8 hours, 400
and kgf / cm ^2, and it held the 400 kgf / cm ² 4 hours. Then, the molding container 5 was taken out of the pressure container 1 and kept at 80 ° C. under atmospheric pressure for 3 hours, and then post-cured. The molding container 5 loses heat resistance near 120 ° C. and is damaged at the final treatment temperature, but since it has been substantially solidified in the curing process at 80 ° C., there is no problem in molding this container.

When the state of occurrence of defects in this molded composite material was examined, peeling was observed at the outermost periphery of this product, but no defects were found inside. On the other hand, instead of the pressure of 400 kgf / cm ² , the pressure of 150 kgf / c
When the generation state of defects in this composite material when m ² was applied was examined, peeling defects were observed in the entire composite material.

[0046]

As described above, according to the method for producing a three-dimensional multiaxial woven fabric composite material of the present invention, a three-dimensional multiaxial woven fabric preform is used as a reinforcing base material and a thermosetting resin is used as a matrix. In the production of the original multiaxial woven fabric composite material, it is possible to inexpensively form a three-dimensional multiaxial woven fabric composite material that is suitable for use conditions and has no defects and excellent mechanical properties. In other words, the pressure vessel and the pressure resistance and heat resistance of the mold can be designed to be necessary and sufficient to withstand the pressure required to prevent the defects of the composite material, thus reducing the device cost. Since it is possible to mold the composite material at a low cost, and if the above pressure is applied at the required time, it is not necessary to maintain this pressure thereafter, and the time occupying the pressure vessel and the mold is shortened, so overall Since the time required for molding can be shortened, the number of composite materials molded per hour can be increased.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a three-dimensional multiaxial woven composite material manufacturing apparatus for carrying out the method of the present invention.

2 (a) to (d) are schematic cross-sectional views showing a structural example of a molding container of the manufacturing apparatus of FIG.

FIG. 3 is an explanatory view showing another three-dimensional multiaxial woven fabric composite material manufacturing apparatus for carrying out the method of the present invention.

FIG. 4 is a graph showing changes in compressibility and specific volume during the curing process of the epoxy resin that constitutes the present composite material.

FIG. 5 is a graph showing the magnitude of pressure required to bring the specific volume of the resin to 0.860 cm ³ / g (20 ° C.) at each stage of the curing process.

[Explanation of symbols]

 1 Pressure vessel 5 Molding vessel 6 Pressure vessel 7 Epoxy resin 8 Three-dimensional triaxial woven fabric preform

Claims (4)

[Claims] 1. A three-dimensional multiaxial woven fabric preform as a base material,
In the method for producing a three-dimensional multi-axial woven composite material using a thermosetting resin as a matrix, the specific volume at the point where the fluidity of the thermosetting resin is substantially eliminated during the curing process of the thermosetting resin is to be used for the composite material. The pressure required to be smaller than the specific volume at temperature is applied at the time when the curing reaction proceeds and the fluidity thereof substantially disappears, and after the fluidity disappears, the pressure is removed. A method for producing a three-dimensional multiaxial woven composite material, which comprises curing. 2. The method for producing a three-dimensional multiaxial woven composite material according to claim 1, wherein the intended temperature of the composite material is room temperature. 3. The method according to claim 1, wherein the three-dimensional multiaxial woven fabric preform is loaded into a volume-variable molding container, and the molding container is filled with a thermosetting resin. It is housed in a pressure container filled with a pressure medium, and the required hydrostatic pressure is applied by pressurizing the pressure medium under a required curing temperature, and after the fluidity of the thermosetting resin disappears, the molding container is A method for producing a three-dimensional multiaxial woven fabric composite material, which is characterized in that it is taken out from the pressure vessel and post-cured. 4. The method according to claim 1, wherein the three-dimensional multiaxial woven fabric preform is loaded into a pressure-resistant mold, and the mold is filled with a thermosetting resin. A necessary pressure is applied to the resin under a curing temperature, and after the fluidity of the thermosetting resin disappears, the three-dimensional multiaxial woven fabric preform is taken out from the mold and post-cured. Method for producing a three-dimensional multiaxial woven composite material.