JP2993791B2 - Low thermal expansion composite material and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite material having low thermal expansion for precision equipment and a method for producing the same.

[0002]

2. Description of the Related Art A composite material is characterized by being capable of designing material properties. For example, a laminated composite material has a wide design area in terms of in-plane characteristics. The coefficient can be designed to be almost zero. Considering the unidirectional continuous fiber reinforced composite material shown in FIG. 7, the thermal expansion coefficient in the fiber axis direction can be maintained approximately from −1 to 0 × 10 ⁻⁶ , although it depends on the fiber content V _f . In the direction perpendicular to the direction, the properties of the matrix are dominant, and in the case of a resin or a metal matrix composite material,
The coefficient of thermal expansion can be designed only to a value of about × 10 ⁻⁶ . If it is in-plane characteristics, it can be designed to have a value of about 1-5 × 10 ^-6 by laminating with changing fiber orientation angle, though not as much as unidirectional continuous fiber reinforced composite material, The characteristics in the direction are difficult to design, and in the case of composite materials for printed wiring boards and IC packaging where the characteristics in the direction are problematic, they have been taken up as a problem to be solved.

[0003]

As described above, in the conventional composite material, the designable range of the thermal expansion coefficient is naturally limited, and the characteristics in the thickness direction of the sheet material are generally strengthened in the same direction. Since the materials are not oriented, there is a problem that material design is almost impossible.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a wide range in which a thermal expansion coefficient can be designed as compared with a general composite material, and furthermore, a composite material which can be easily designed. It is an object to provide a material and a method for manufacturing the same.

[0005]

SUMMARY OF THE INVENTION According to the present invention, low thermal expansion is provided.
Composite material dispersed in matrix, this matrix
Has a higher modulus of elasticity than that of
A reinforcement having a lower modulus than that of the matrix, and
Voids, cracks or bullets dispersed in the above matrix
The modulus is at least one order of magnitude lower than that of the above matrix
Those with fillers and the above-mentioned reinforcing materials are three-dimensionally combined
It has been forgotten. In addition, the low thermal expansion according to the present invention.
The method of manufacturing the upholstery composite material combines the three-dimensional reinforcement
To obtain a preform by matrices
Immersing the resin in the resin, and
Pull up from the matrix resin to the preform
Those who perform the process of curing the adhering matrix resin
Wherein the modulus of elasticity of the reinforcement is
Higher than that, the coefficient of thermal expansion of the reinforcement
It is a lower method than that of Kusu. That is, the low-thermal-expansion composite material according to the present invention has conventionally introduced artificial voids and cracks for lowering the thermal expansion, in addition to the matrix, which is a constituent material of the composite material, and reinforcing materials such as fibers and particles. It is dispersed. As a method for dispersing the required amount of voids and cracks as uniformly as possible in the matrix material, three methods were used, and the first method utilized a mismatch in thermal distortion during molding. That is, a filler having a larger thermal expansion coefficient than that of the matrix material is mixed and dispersed, and the filler / matrix interface is separated by a thermal stress caused by a difference in thermal expansion coefficient between the filler and the matrix resin, thereby substantially reducing the filler portion. Now visible as an upper void. In the second method, a so-called penny-shaped crack was introduced in a direction perpendicular to the fiber by utilizing thermal stress in the fiber-reinforced composite material. In the third method, a method of leaving a non-impregnated portion in the three-dimensional reinforced composite material to form a porous structure was used. In the above description, voids and cracks are specified, but these portions need only have an elastic modulus lower by at least one order than the matrix. For example, the same effect can be obtained even in a system in which rubber particles are dispersed in a resin matrix. is there.

[0006]

The low thermal expansion composite material of the present invention has a filler whose elastic modulus is at least one order of magnitude lower than that of voids, cracks, or matrix introduced into the composite material. As a result, a compressive force acts. The collapse of the voids caused by the compressive force is the mechanism for reducing the thermal expansion of the composite material according to the present invention. In order for such a compressive force to act, it is required that the elastic modulus of the reinforcing material is higher than that of the matrix, and that the thermal expansion coefficient of the reinforcing material is lower than that of the matrix.

[0007]

【Example】

Embodiment 1 FIG. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram of the microstructure of a particle-dispersed composite material, in which 1 indicates a reinforcing material, 2 indicates a void, and 3 indicates a matrix region. In this embodiment, silica particles (Young's modulus: 7000 kg / mm ^-2 , thermal expansion coefficient: 1 × 10 ^-7 ) as a reinforcing material, and a bismaleimide resin or an epoxy resin (Young's modulus: 300 kg / mm) as a matrix.
^-2 , thermal expansion coefficient: 6.8 × 10 ^-5 ), and spherical particles of silicon rubber (Toray Silicon Trefil E60) are used as a material for dispersing voids in the matrix.
0) was used. That is, the thermal expansion coefficient of silicone rubber is 3.2
× 10 ^-4 and higher than 6.8 × 10 ^{-5 of the} matrix. As shown in FIG. 2, mismatch thermal stress generated at the matrix / silicon rubber interface during the temperature drop from the resin curing temperature during molding to room temperature. This causes the interface to be peeled off, so that the silicone rubber region can be substantially regarded as a void.
When a bismaleimide resin was used, the same material was prepared by a premix method. That is, a slurry (suspension) in which a predetermined amount of silica particles and silicon powder are mixed in a varnish composed of a solvent (N-methyl-2-pyrrolidone) and a bismaleimide resin becomes a solvent for the bismaleimide resin and becomes soluble in the solvent. A certain amount of methanol is dropped while being stirred at high speed, and the separated resin-adhered silica particles and silicon powder are collected. The recovered material was subjected to pressure and heat molding to obtain a composite material as shown in FIG.

In the case of an epoxy resin, it was prepared by a kneading method. That is, a predetermined amount of silica particles and silicon powder were mixed and mixed in an epoxy resin using two rolls, and the mixture was subjected to pressure thermoforming to obtain a composite material as shown in FIG.

[0009] Figure 3 shows changes by V _v is the void volume fraction of the composite material obtained in the previous section of the way the thermal expansion coefficient of the (epoxy resin) (CTE), the volume fraction ratio V _f of the silica particles 56%. As shown, the coefficient of thermal expansion decreases as the void fraction increases. This decrease in the coefficient of thermal expansion is due to a mechanism in which a compressive stress is generated around the silica particles due to the presence of the silica particles, and the voids shrink due to the compressive stress. Note that the solid line is a predicted value by the equivalent inclusion method, but it can be seen that the rate of decrease in the coefficient of thermal expansion can be designed using the existing compound rule (by the equivalent inclusion method). In this example, a composite material in which the material is a silica particle / hour resin matrix is used, but the mechanism of the present invention works when the elastic modulus of the reinforcing material is higher and the coefficient of thermal expansion is lower than that of the matrix. Therefore, the material system may be a metal-based or ceramic-based composite material. Although voids and cracks are specified in the above description, it is sufficient that these portions have an elastic modulus lower by at least one order than that of the matrix. For example, a system in which rubber particles are dispersed in a resin matrix has the same effect.

Embodiment 2 FIG. In Example 1, spherical particles of silica were used as the reinforcing material, but the effect of parameters related to the material was evaluated by using the equivalent inclusion method that was effective in the prediction of FIG. 3 to determine the thermal expansion coefficient of the void-containing composite material. According to the results of the study, in order to efficiently reduce the coefficient of thermal expansion, a fibrous material having a high elastic modulus is preferable as a reinforcing material, and the shape of voids (voids or cracks) is more fibrous than spherical. Things are better. So, as the next example,
The case where fibers are used as the reinforcing material is shown.

In this embodiment, ICI alumina short fiber sapphire is used as a reinforcing material, and silicon rubber fine particles are used as a void generation source in the same manner as described above. In producing the composite material, first, a mixture of the reinforcing material and the silicone rubber was preformed in a mat shape. The papermaking method was applied for the preparation of the preform. In a normal papermaking method, water is used as a medium for dispersing pulp fibers.Since silicon rubber is difficult to uniformly disperse in water,
Isopropyl alcohol was used as a medium instead of water in the papermaking liquid of the preform. That is, a predetermined amount of alumina short fibers and silicon rubber particles are dispersed in isopropyl alcohol, and microfibrillated cellulose serving as a binder of the preform is mixed therein at about 3% by weight of saphir, and sufficiently stirred. At this time, if the concentration of the alumina short fibers in the isopropyl alcohol is 3% by weight or less, the alumina short fibers can be easily and uniformly dispersed without entanglement. Next, the suspension uniformly dispersed is suction-filtered at a high speed to obtain a mat-shaped preform. The alumina short fibers in the preform produced by the papermaking method in this manner are almost two-dimensionally randomly oriented, and thus the obtained composite material shows in-plane isotropy.

The preformed body obtained as described above is
It has a porous structure with many voids and low fiber content. Therefore, when the resin is impregnated with the resin and subjected to pressure and heat molding, the fiber content can be changed by changing the compression ratio.
However, if the material is excessively compressed, the sapphire, which is a reinforcing fiber, breaks and the reinforcing effect is significantly reduced. Therefore, the upper limit of the fiber content _Vf is about 40%. The following table shows the measured values of the coefficient of thermal expansion of the prototypes.

[0013]

[Table 1]

In the table, α _L and α _T are the in-plane and out-of-plane thermal expansion coefficients, respectively. In this example, a composite material whose material is an alumina short fiber / epoxy resin matrix is used. However, the mechanism of the present invention works when the elastic modulus of the reinforcing material is higher and the coefficient of thermal expansion is lower than that of the matrix. . Therefore, the material diameter may be a composite material using fibers having high rigidity and low thermal expansion as compared with a metal-based or ceramic-based material. Although voids and cracks are specified in the above description, it is sufficient that these portions have an elastic modulus lower by at least one order than that of the matrix. For example, a system in which rubber particles are dispersed in a resin matrix has the same effect.

Embodiment 3 FIG. The effect of voids or cracks is expected to be more pronounced when the shape is flat and the plane that is flat with respect to the fiber axis is oriented at right angles, according to the above-described equivalent inclusion method. Therefore, such cracks were generated by subjecting the [0,90 °] symmetric laminate to a heat cycle. The generated transversal cracks are as shown in FIG. 4, and are arranged at substantially constant intervals s. In this trial production, a laminated board composed of continuous carbon fiber (Toray M40) / epoxy resin and having the structure shown in FIG. 4 was manufactured by changing the fiber content, and liquid nitrogen (−196 ° C.) and boiling water (100 ° C.) were used.
C.). The in-plane coefficient of thermal expansion α _L of the laminate obtained from this molded product is shown in the table below.

[0016]

[Table 2]

In the table, L-1 and L-4 have no heat cycle, L-2 and L5 have five heat cycles, L-3 and L-
No. 6 is after 20 heat cycles. Note that, in this example, the composite material in which the material is a carbon continuous fiber / epoxy resin matrix is used, but the mechanism of the present invention works when the elastic modulus of the reinforcing material is higher and the coefficient of thermal expansion is lower than that of the matrix. . Therefore, any material may be used as long as it is a composite material using fibers having higher rigidity and lower thermal expansion than metal-based or ceramic-based materials.

Embodiment 4 FIG. The above ones mainly reduce only the enhanced in-plane coefficient of thermal expansion.
In this example, a material capable of three-dimensionally controlling the coefficient of thermal expansion that causes voids or cracks in a three-dimensionally reinforced composite material is illustrated. As a material for three-dimensional strengthening, a one-way strengthened small diameter rod made here by a pultrusion method was assembled and used as shown in FIG. Although various types of three-dimensional reinforcing structures other than the three types shown in FIG. 5 are known, the following embodiment mainly deals with a three-dimensional reinforcing structure. The small-diameter rod used was a carbon fiber (Torr
ayM46J) / diameter 0.6 composed of epoxy resin
8 mm, 65% fiber content. In order to obtain a three-dimensional reinforced composite material, a dipping method was used in which a preform as shown in FIG. 5 was immersed in a resin (varnish) diluted with a solvent, and then pulled and heated and cured in an oven. The amount of the resin adhered was changed by changing the varnish concentration or increasing or decreasing the number of repetitions of the dipping method.

The thermal expansion coefficient α of the triaxial three-dimensionally reinforced porous composite material behaves as shown in FIG. VRE on the horizontal axis in the figure is
The figure shows the volume ratio of the matrix resin attached by the dipping method occupying the volume other than the rod in the preform. Therefore, VRE = 0 indicates the state of the preform to which no resin is attached, and VRE = 1
00% represents a normal three-dimensional reinforced composite material in which voids are completely filled with resin. From this figure, it can be seen that the three-dimensional reinforced composite material has a higher molding residual stress than a general two-dimensional composite material, and the thermal expansion coefficient is rapidly lowered by the inclusion of voids. However, the decrease is also VRE = 8
Up to about 0%, stable 1 in the region of VRE <80%
× 10 ⁻⁶ <α <2 × 10 ⁻⁶ .
In addition to the triaxial reinforcement, the case of four-axis reinforcement and seven-axis reinforcement was examined, and it was found that the same behavior was exhibited. However, in the four axes, the thermal expansion coefficient of the stable region is 0 × 10 ⁻⁶ <α <1 × 10
⁻⁶ , and −1 × 10 ⁻⁶ <α <0 in seven axes.
× is in the range of 10 ^-6, triaxial, four axes and three-dimensionally -1 × thermal expansion coefficient Together tripartite Nanajiku ^10-6 <alpha <2
It can be seen that it can be precisely controlled in the range of × 10 ^-6 .

[0020]

As described above, the low thermal expansion composite of the present invention
The material is a matrix, dispersed in this matrix, elastic
Rate is higher than that of the above matrix and the coefficient of thermal expansion is higher
A lower reinforcement than that of the matrix,
Voids, cracks or modulus of elasticity
Fillers one order of magnitude lower than those of the above matrix
And the low thermal expansion composite material of the present invention.
The method of manufacturing the preform is based on a pre-
Process to obtain the preform
A step of immersing the preform in the fat
Pulled up from Rix resin and adhered to the above preform
A method of performing the step of curing the matrix resin.
The modulus of the reinforcement is greater than that of the matrix
High, the coefficient of thermal expansion of the reinforcement is higher than that of the matrix.
A lower method than Re, the thermal expansion coefficient of the composite material can be greatly reduced as compared with the conventional, there is an effect that the Ru can be extended thermal expansion design range of conventional composite material increases. In addition, this material has a useful effect as a material for precision equipment which does not want to be deformed by temperature, and as a material for a composite structure or the like where it is desired to match the thermal expansion coefficient with other members.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a particle-dispersed low thermal expansion composite material according to one embodiment of the present invention.

FIG. 2 is an explanatory view showing a mechanism of void generation in one embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between the void fraction and the coefficient of thermal expansion in the particle-dispersed low thermal expansion composite material according to one embodiment of the present invention.

FIG. 4 is a material configuration diagram of a carbon continuous fiber reinforced low thermal expansion composite material according to an embodiment of the present invention.

FIG. 5 is a conceptual diagram of a three-dimensional reinforcing preform used in an embodiment of the present invention.

FIG. 6 shows a resin filling rate VRE and a thermal expansion coefficient α in a triaxial three-dimensional reinforced low thermal expansion composite material according to an embodiment of the present invention.
FIG.

FIG. 7 is a material configuration diagram of a unidirectional reinforced continuous fiber reinforced composite material which is a conventional material.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reinforcement material 2 Void 3 Matrix 4 Silicon rubber fine particle 5 Crack 6 Reinforcement fiber bundle 7 Crack spacing 8 Reinforcement fiber

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ identification symbol FI C08K 7/18 B29C 67/14 G // B29K 105: 06 (58) Field surveyed (Int.Cl. ⁶ , DB name) C08L 1/00-101/14 B29C 43/02 B29C 67/14

Claims (3)

(57) [Claims] A matrix, dispersed in the matrix
Has a higher modulus of elasticity than that of
A reinforcement having a lower modulus than that of the matrix, and
Voids, cracks or bullets dispersed in the above matrix
The modulus is at least one order of magnitude lower than that of the above matrix
Low thermal expansion composite material with filler . 2. The reinforcing material is three-dimensionally combined.
The low thermal expansion composite material according to claim 1, wherein: 3. A prefoamer comprising three-dimensionally combining reinforcing materials.
The process of obtaining a preform
Immersing the preform in the matrices
From the resin and adhered to the above preform
A method of curing the matrix resin.
The modulus of the reinforcement is greater than that of the matrix
High, the coefficient of thermal expansion of the reinforcement is higher than that of the matrix.
For producing a low thermal expansion composite material characterized by a lower thermal expansion
Law.