JPS6410583B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a short material used as a fibrous skeleton when forming a fiber-reinforced composite material by infiltrating or impregnating matrix materials such as metals, alloys, or various plastics. The present invention relates to a method for manufacturing a fiber aggregate preform, particularly a short fiber oriented preform having a texture in which fiber materials are aligned in a fixed direction.

[Conventional technology]

Composite materials reinforced with various types of short fibers, including single crystal whiskers such as carbides and nitrides, chopped fibers such as glass fibers, alumina fibers, and carbon fibers, have mechanical strength depending on the orientation of the short fibers they fill. It is known to have a large effect on physical and electrical properties. For this reason, there are many studies aimed at the orientation of fibers.

Orientation techniques for short fiber reinforcement in composites are roughly divided into composite orientation methods and preform orientation methods.

The composite orientation method is a method in which short fiber reinforcing materials are randomly dispersed and mixed in a liquid matrix in advance, the short fibers are arranged in a certain direction using some kind of means, and then the matrix is solidified. As a typical example, a method is known in which a matrix mixed with short fiber reinforcement is extruded in a viscous state through a nozzle or slit, and the mixed short fibers are arranged in the extrusion direction by the flow gradient. In addition, as a special orientation technique, a large number of small bubbles are generated in a mixed dispersion of short fibers and a matrix, or a large number of solid particles with a specific gravity higher than that of the dispersion are added, and the floating of air bubbles or the movement of solid particles is performed. A method of increasing the degree of orientation by applying a couple to dispersed short fibers (Japanese Patent Application Laid-Open No. 59-55719),
Alternatively, a method using electric flocking, which involves applying the action of electrostatic power lines to short fibers and aligning and adhering them to the surface of a resin matrix (Japanese Patent Application Laid-Open No. 1983-20963)
etc. have been proposed.

The preform orientation method is a method in which short fibers form an aggregate preform showing a predetermined orientation, and this is impregnated with a matrix of liquid plastic or molten metal to solidify it. Applicable to molten metal compounding methods including An example of a preform orientation method is a method in which short fibers are mixed and dispersed in a liquid such as alcohol, poured into a rotating mold, and centrifuged to form an oriented pile of short fibers on the wall of the container (Unexamined Japanese Patent Publication No. Showa 49
-86450) is known.

[Problem that the invention seeks to solve]

Among the above composite orientation methods, the extrusion orientation method has the disadvantage that the degree of alignment decreases as the fiber content increases, so short fibers cannot be effectively aligned unless the extrusion operation is repeated, especially when using a metal matrix. There is. In addition, special orientation techniques that utilize force couples or electrostatic forces have practical difficulties because insertion is complicated.

Similarly, the centrifugal molding method used in the preform orientation method also has drawbacks in that it is complicated to operate and requires complicated equipment.

The present invention provides a method for manufacturing short fiber oriented preforms that improves the problems of these conventional methods.

[Means for solving problems]

The present invention skillfully incorporates the method used in the composite orientation method into preform orientation, and its structure is such that short fibers are dispersed in melted paraffin, excess paraffin is removed, and then short fibers are dispersed in melted paraffin. It is characterized by extruding fiber-containing paraffin from a nozzle or slit while keeping it in a plastic state, cooling and solidifying it, and heating the formed solid body to 400 to 500°C to completely remove the paraffin component.

Short fiber materials that serve as reinforcing materials include SiC,
Inorganic whiskers such as Si ₃ N ₄ , Al ₂ O ₃ , AlN or graphite, glass fiber, carbon fiber or
Target fibers include chopped fibers made from SiO ₂ / Al ₂ O ₃ fibers.

Paraffin is liquefied by heating it to a temperature above its melting point (45 to 65°C), and the short fibers are put into it and stirred well. Excess paraffin is removed from the obtained paraffin dispersion of short fibers, and the final fiber density is adjusted to an arbitrary fiber density within a range that allows the texture of only short fibers to be formed. Excess paraffin is removed by overtreatment or the like.

Next, the short fiber-containing paraffin is slowly cooled to near the glass transition point, and extruded from the nozzle or slit of an extrusion molding device while maintaining its plastic state. The extrusion operation is repeated as necessary, and in this process the short fibers are arranged parallel to the extrusion direction.

The short fiber-containing paraffin is cooled and solidified after the extrusion process. At this time, it is possible to solidify into various shapes by selecting the shape mechanism of the nozzle or slit of the extrusion molding device, and by stacking or arranging and joining the plastic extrudates.

The formed short fiber-containing paraffin solid is
Finally, the paraffin component is completely removed by heating to a temperature of 400°C or higher in the air to melt and incinerate the paraffin component.

The short fiber preform produced in this manner has an extremely homogeneous structure in which the short fibers are oriented in two-dimensional directions. This short fiber oriented preform exhibits a monolithic structure that is sufficient to withstand compositing even in its original state, but if the fiber content is low, it may be necessary to apply a dilute binder solution such as water glass or thermosetting resin to the outer surface. It can also be applied or sprayed to provide a reinforced skeleton.

[Effect]

According to the present invention, individual short fibers are oriented extremely smoothly without damage due to the highly lubricious flow gradient effect peculiar to paraffin accompanying the extrusion process. Therefore, an effective alignment state is generated within a short time. Further, since paraffin is completely removed after fulfilling the above-mentioned orientation function, it does not have any adverse effect on compounding.

〔Example〕

Diameter 0.5-1.5μm, length 50-100μm, density 3.18
SiC whiskers having the properties of g/cm ³ and β-type crystal were placed in paraffin of 10 to 100 times the weight melted on a water bath, and sufficiently dispersed by stirring. Next, the dispersion liquid was poured into a heating device, and while maintaining the temperature, pressure was applied from above to remove excess paraffin.

The SiC whisker-containing paraffin recovered as excess residue was gradually cooled to a paste-like viscous state, and extruded from the nozzle of an extrusion molding device (squeezing ratio 0.5) while maintaining this plastic state. Subsequently, this extrusion process was repeated twice and then cooled to form a cylindrical solid body.

The formed solid body was transferred to an electric furnace and heated to 500 m
The paraffin component was completely incinerated and removed by heating to a temperature of .degree.

The thus obtained SiC whisker preform was a cylindrical aggregate of homogeneous structure in which SiC whiskers were uniformly arranged along the axial direction, and had a bulk density of 0.64 g/cm ³ .

[Effects of the Invention] By applying the present invention, the following various industrial effects are brought about.

(1) The method is simple and there is no need to use complicated equipment, so it is suitable for mass production.

(2) Since the short fibers are smoothly oriented due to the sliding action peculiar to paraffin, it is possible to produce a short fiber oriented preform with high properties without damaging the short fibers.

(3) It is possible to store or transport the extruded solid (intermediate) of paraffin containing short fibers, and remove the paraffin immediately before compositing, thereby avoiding phenomena such as damage or deformation of the preform during the handling stage. It will be done.

(4) Composite material (FRP,
Since the mechanical and electrical properties of FRM, FRC) are greatly improved, it is useful in fields that require high performance properties such as aircraft parts and automobile parts.

Claims (1)

[Claims] 1 After dispersing short fibers in molten paraffin, remove excess paraffin, then extrude the short fiber-containing paraffin from a nozzle or slit while keeping it in a plastic state, cool and solidify it, and heat the formed solid at 400°C or higher. A method for producing a short fiber oriented preform, characterized by completely removing paraffin components by heating to a high temperature.