JPH0135932B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a whisker preform used as a fiber skeleton when manufacturing a whisker-reinforced composite material by infiltrating or impregnating a matrix material such as a metal, alloy, or plastic. Various types of whiskers composed of single crystals such as SiC, Si ₃ , N ₄ , and graphite have unique characteristics such as extremely high levels of strength, modulus of elasticity, heat resistance, and chemical stability, so they have long been used as metals or plastics. Although it is considered useful as a composite reinforcing material, it has not yet reached the stage of practical use. The most important technical reason for this is that it is extremely difficult to homogeneously mix and disperse whiskers into the matrix material. That is, whiskers are produced by high-temperature reactions of various whisker raw materials, and the resulting product has a structure in which dense short fibrous whiskers are intertwined in a non-directional manner and cannot be easily resolved. This impairs homogeneous dispersion in matrix materials, and is a factor that impedes practical application. The applicant focused on the fact that the form of whiskers produced can be converted into a sponge-like cake with an extremely uniform pore structure depending on the selection of the reaction system, and the applicant introduced a matrix substance into the spongy cake of the produced whiskers, using it as a fibrous skeleton. We have developed a manufacturing technology for SiC whisker-reinforced composite materials by interposing them, and have already proposed it in Japanese Patent Application No. 130293/1983. However, this method has the disadvantage that a homogeneous tissue skeleton cannot be formed unless the whisker generation conditions are extremely strictly controlled, resulting in local variations in the quality characteristics of the resulting composite material due to segregation. Ta. The present invention solves the difficulties of the prior art and provides a method for manufacturing a whisker preform that always provides homogeneous composite properties without local segregation.
Its composition is whisker product, resin 0.1~10
It is characterized in that it is dispersed in a solution containing 100% and passed through a sieve, and then the remaining wet whisker cake is dried as it is or after being compressed to a predetermined density. The whisker products used as raw materials include SiC,
Diameter 0.1~5μ composed of Si ₃ N ₄ or graphite
The whiskers having a length of 10 to 500 μm are used, but the effects of the present invention are particularly effective when using minute whiskers with an aspect ratio of 50 or less as a raw material. The whisker product, which usually has a nodular cake-like structure in which short fibers are nondirectionally intertwined, is first disentangled or compressed and then dispersed in a dilute resin-containing solution. Examples of resin-containing solutions include aqueous solutions of polyvinyl alcohol or carboxyl methyl cellulose, acetone solutions of epoxy, polystyrene, polyvinyl chloride or polymethyl methacrylate resins, benzene solutions of polystyrene or silicone resins, or alcoholic solutions of polyvinyl butyral or polyvinyl acetate resins. It is preferable to use a solution. It is important to set the resin concentration in the solution in the range of 0.1 to 10%, and if it is less than 0.1%, the aspect ratio
It becomes difficult to maintain the shape of the preform formed by micro whiskers of 50 or less, and
Concentrations exceeding 10% result in inhibiting the smooth penetration of matrix materials during composite material creation.
The whisker product is dispersed in the resin-containing solution by adding the whisker product to the resin-containing solution in a weight ratio of 5 times or more, preferably 7 to 50 times, and using a stirring device such as a mixer or a magnetic stirrer. This is done by stirring until the whiskers are uniformly dispersed. The dispersion solution is then passed through a sieve to separate poorly dispersed nodular whisker components. Sieve is 32-100
It is preferable to use a mesh with coarser meshes, as there is a risk that small cakes with entangled whiskers may pass through, whereas finer meshes of more than 100 meshes will trap even the effective whisker components. This is not desirable as it causes inconvenience. After passing through the sieve, the dispersion solution is subsequently passed through a filter such as paper or glass filter to separate most of the resin-containing solution as a liquid. The remaining whisker component is formed as a cake-like material moistened with resin liquid. The wet whisker cake is dried as it is or after being compressed to a desired density considering the Vf value, shape, etc. when made into a composite material. The whisker preform manufactured in this way has an extremely homogeneous structure in which whiskers with uniform properties are arranged in a two-dimensional non-directional manner, and also has a low aspect ratio due to the caking effect of the intervening resin.
Even when using micro whiskers of 50 or less as raw materials, an integral shape that does not disintegrate during handling is provided. The whisker preform obtained by the present invention is
This is used as a fiber skeleton and Mg, Al, Si, Ti, Cr, Mn,
Infiltration of matrix materials selected from metals such as Fe, Co, Ni, Cu, Zn, Ag, Ta, and W, or their alloys, and various plastics such as epoxy resins, polyester resins, phenol resins, polyimide resins, and urea resins. Alternatively, it is made into a composite by impregnating it. At this time, the resin present inside the whisker preform does not impede the penetration of the matrix material at all, and it penetrates smoothly throughout the tissue. Therefore, the formed composite material (FRP,
FRM) can always be given homogeneous and high-performance reinforcement properties with extremely little local variation in properties. Hereinafter, the present invention will be explained based on examples. Example 1 A reaction vessel was filled with a blended raw material of silicon source material and carbonaceous material, and heated in a heating furnace maintained in a non-oxidizing atmosphere.
After being held at 16,000℃ for 4 hours, the residual carbonaceous components were burned off and the resulting product was made up of minute SiC whiskers (β-type single crystal) with a diameter of 0.5 to 1.0μm and an aspect ratio of 50 or less, with a bulk density of 0.04g/cm ³ , average A spongy cake with a porosity of 98.7% was obtained. After the above whisker product was previously compressed, 84 g was placed in a Juicer mixer together with 2000 ml of resin-containing solutions of different concentrations, and the mixture was rotated and stirred for 10 seconds to uniformly disperse the whiskers. As resin-containing solutions, polyvinyl alcohol aqueous solution (PVA), polyvinyl chloride resin acetone solution (PVC), and epoxy resin acetone solution (EP) were used. The dispersion solution was passed through a 55 mesh sieve and subsequently through a 200 mm diameter paper using an absorber.
The remaining wet whisker cake (thickness: 8 mm) was peeled off from the paper and cut with a cutter to create 10 specimens with a width of 10 mm and a length of 120 mm. Each specimen was compressed in a mold while still wet and then dried to produce a SiC whisker preform having a shape of 10 mm in width, 120 mm in length, and 4 mm in thickness and a bulk density of 0.63 g/CC. The obtained SiC whisker preform had an integral morphology that did not easily collapse. Each whisker preform is made into a fiber skeleton, which is vacuum impregnated with epoxy resin liquid and then hot-pressed.
Made into FRP. The apparent specific gravity, flexural modulus, and flexural strength of each FRP formed were measured, and the average values and standard deviations are shown in the table.

[Table] From the results in the table, when the concentration of the resin-containing solution used is 1.0 to 10%, there is very little variation in properties and an FRP with a homogeneous structure without local segregation can be obtained, but when the concentration is 12% When this happens, the smooth impregnation of the matrix resin is inhibited and the characteristic values and variations become large. Incidentally, when a SiC whisker preform was manufactured under the same conditions using a solution containing 0.05% resin, it was extremely easy to disintegrate and it was difficult to use it for compounding. Example 2 Beta-type SiC whiskers with a diameter of 0.5 to 1.5 μm and a length of 10 to 300 μm, bulk density of 0.04 g/cm ³ , average porosity
Easily loosens 98.7% of spongy products,
A polyvinyl acetate resin alcohol solution with a resin concentration of 1.0% was added to 100 g of the mixture, and the mixture was stirred until uniformly dispersed. The dispersion solution was then passed through a 55-mesh sieve, and then absorbed using paper with a diameter of 50 mm. Peel the remaining wet whisker cake from the paper and
A cylindrical whisker preform having a bulk density of 0.283 g/cc and having a diameter of 50 mm and a height of 200 mm was produced by drying as it was. The above whisker preform was sliced into rings of 40 mm each to form a fiber skeleton (5 pieces), which was then infiltrated with molten aluminum at a pressure of 1 ton/ ^cm3 .
Converted to FRM. The apparent specific gravity, tensile modulus, and tensile strength of each FRM were measured and shown in the table along with the standard deviation of the measured values. For comparison, the resulting whisker cake was compressed without disassembly and had a bulk density of 0.63 g/cc and a diameter of 50 mm.
A cylindrical cake with a height of 200 mm and a height of 200 mm was sliced into 40 mm thick rounds to obtain a fiber skeleton, and pure aluminum was infiltrated using the same method to form FRM. The strength characteristics of each FRM obtained are shown in the table (comparative example).

[Table] In the table, the Vf value of the FRM according to the present invention is
The Vf value of the comparative example is 12.8%, and the Vf value of the comparative example is 27.7%, so the comparative example has higher strength characteristics, but the variation in each characteristic value is significantly reduced in the inventive example. It was observed that it exhibited a homogeneous structure without segregation. Example 3 Same as Example 1 except that a cake of Si ₃ N ₄ whiskers with a diameter of 0.2 to 0.5 μm and a length of 50 to 300 μm was used as the raw material, and a polystyrene resin benzole solution with a concentration of 1% was used as the resin-containing solution. By conditional method
We fabricated a Si ₃ N ₄ whisker preform and FRP using this as a fiber skeleton. Due to the resulting epoxy resin matrix
The intensity characteristics of the ERP were measured and shown in the table along with the standard deviation.

【table】

[Table] The results shown in the table indicate that the obtained FRP had an extremely homogeneous structure as a whole.

Claims (1)

[Claims] 1. The whisker product is dispersed in a resin-containing solution with a concentration of 0.1 to 10%, passed through a sieve, and the remaining wet whisker cake is dried as it is or compressed to a predetermined density. A method for manufacturing a whisker preform for composite materials, characterized by processing. 2. The resin-containing solution with a concentration of 0.1 to 10% is an aqueous solution of polyvinyl alcohol or carboxyl methyl cellulose, an acetone solution of epoxy, polystyrene, polyvinyl chloride or polymethyl methacrylate resin, a benzene solution of polystyrene or silicone resin, or a polyvinyl butyral or The method for producing a whisker preform for a composite material according to claim 1, which is an alcohol solution of polyvinyl acetate resin.