JPS5955719A - Fiber arrangement of composite material filled with short fibers - Google Patents

Abstract

PURPOSE:To make possible the orientation of short fibers in the length-wise direction by a method wherein in mixed fiber dispersing liquid containing short fibers and matrix couples are given to short fibers by generation of many bubbles or by movement of introduced solid grains larger in specific gravity than the liquid. CONSTITUTION:In a 1st and 2nd mixing tank, matrix material, short fibers, hardener, viscosity modifier, etc. are mixed uniformly and before these materials are hardened, rows of prescribed small bubbles (a) are discharged from bubble nozzles 7 into fiber dispersing liquid filled in a molding tank 10. The small bubbles are lifted by buoyancy vertically out of the fiber dispersing liquid and coincide with short fibers placed obliquely in the moving direction of the bubbles. By means of the turning moment due to coincidence with the bubbles the short fibers change their postures to the moving directions of the bubbles to lift fiber orientation. The fiber dispersing liquid with lifted orientation in the molding tank 10 undergoes air-release function in a reduction tank 11, is hardened and molded under prescribed heating conditions to obtain fiber packed composite material having high fiber orientation.

Description

DETAILED DESCRIPTION OF THE INVENTION The fiber arrangement state of a composite material filled with short fibers as a reinforcing material affects many material properties such as mechanical properties and electrical properties. The present invention proposes a means for actively arranging short fibers mixed within a matrix in a desired direction in order to obtain a composite material having desired material properties.

When molding composite materials filled with fibers using conventional molding methods such as transfer molding, injection molding, and compression molding, during the molding process, the fiber dispersion liquid consisting of fibers and matrix (resin, etc.) is molded into complex shapes. It has been pointed out that since the fibers flow at different speeds in the flow path, the fibers are arranged in a directional manner. This is because fluid shearing force accompanying the fiber alignment and flow acts on the fibers in the molding process that involves the flow of a fiber dispersion liquid using such a matrix material as a medium. The factors involved in fiber arrangement in this case are the shape and pressure of the cavity, which is the final shaping part of the product, and the flow path leading to it.

These are molding factors such as flow rate, and material properties such as the viscosity and fiber properties of the matrix material. On the other hand, all of these factors are strongly intertwined with the shape and formability of the mature cedar part.
It is not possible to set it arbitrarily only from the aspect of fiber arrangement.

Therefore, it has been difficult to obtain the desired fiber arrangement solely by the flow of the material during the molding process.

The present invention effectively orients short fibers by the moving action of small bubbles or solid particles supplied into a short fiber dispersion liquid using a matrix such as a resin, without imparting flow to the matrix or fibers. , short ta with high fiber orientation
This paper proposes a method for obtaining fiber composite materials.

Therefore, in the vA fiber arrangement method of the present invention, when molding a composite material filled with short fibers, a large number of small bubbles are generated in a fiber dispersion liquid in which short fibers and a matrix are mixed, and the floating of the bubbles causes the above-mentioned By applying a couple force to the fibers, or by placing a large number of solid particles having a specific gravity higher than that of the liquid in a fiber dispersion liquid that is a mixture of short fibers and a matrix, and by moving the solid particles, a couple force is applied to the short fibers. It is characterized in that the length direction of the short fibers is oriented in the direction of movement of air bubbles or solid particles, thereby increasing the degree of orientation of 'El jl & flu.

Polyacrylamide aqueous solution (jelly shear viscosity near, 4*
Is) was used. In addition, a tank made of transparent acrylic resin plate with a height of 25QIllJl, width E, 40zg, and inner thickness of 50mm was used in the experiment, and the above fiber dispersion liquid (
The fiber optical density was 01%), and air bubbles were generated by injecting compressed air from the tip of a nozzle 7 with an inner diameter of 05 ml provided at the bottom of the tank. The size of the bubbles in this case is approximately 6n~l
0KII, the ascent speed is 20cm/! It was 扛~2δα range.

It shows the difference in the identified position after bubbles are continuously generated and defoamed. Although the orientation angle of the m-fibers varies somewhat depending on the measurement location, the frequency at which fibers 〈θ〉90°) aligned in the vertical direction (the direction of bubble movement) are observed is approximately 5% to 5% before treatment with bubbles. 30%, but if the material can be molded by processing with bubbles,
organic material.

Both inorganic and metallic materials can be used. For example, thermosetting resins such as epoxy resin flit, which is a liquid (monomer) at low temperatures and hardens by heating in the presence of a hardening agent, thermoplastic 4M resins such as polyethylene, which become melted when heated, or Various metals and the like are used to form a melt.

In addition, fibers include so-called voice cars, flocks, staple fibers, etc., which have a length greater than their diameter, and short fibers.The types include whiskers such as ceramics and metals, and inorganic fibers such as asbestos, carbon fibers, and glass fibers. First, nylon, vinylon, etc.
! A fiber etc.

The type of IJ lux material mentioned above, the type and shape of short fibers, the mixing ratio between fibers with different characteristics, and the composite ratio of matrix and fibers are appropriate depending on the performance required as a composite material. stipulated in

FIG. 3 shows an outline of an apparatus for molding a composite material with a high degree of texture orientation using an epoxy resin, which is a thermosetting resin, as a matrix and a carbon fiber having a large stiffening effect as a filling material, by the method of the present invention. . The carbon fiber toeboxyl monomer, which has been cut to a required length in advance, is mixed in a first mixing tank 1 into a uniform fiber dispersion liquid having a predetermined composite ratio. This fiber dispersion liquid is transferred to a second mixing tank 3 by a pump 2, where it is uniformly mixed with a curing agent supplied from a curing agent preparation tank 4, and then passed through a pipe line with a valve 5 into a large number of bubbles. A bubble generating tank 9 equipped with a noggle 7 and a forming tank 10 connected to the bubble generating tank 9 are filled with the foam. A vacuum tank 11 is connected to the molding tank 10 to completely remove air bubbles generated in the fiber dispersion liquid (defoaming).

A conduit 8 in which a large number of bubble nozzles 7 are buried is connected to a compressor 14 via a solenoid valve 13, and the air from the compressor 14 is sent from the tip of the bubble nozzle 7 to the discharge amount and the discharge amount by the solenoid valve 3. The time interval is adjusted and the bubbles are ejected in a line.

Matrix material in the first and second mixing tanks.

Let it come out. Due to buoyancy, these small bubbles float along a vertical line in the tlaJ dispersion liquid and collide with short fibers located obliquely in the direction of bubble movement. The short fibers change their posture in the direction of movement of the bubbles due to the rotational moment caused by the collision of the bubbles, and the degree of 988 orientation is increased.

When the distance between the cell rows is relatively large, the matrix material located between the cell rows is pulled by the movement of the bubbles and a local flow occurs, resulting in a swirling flow between the cell rows and the fiber changes the orientation angle in the direction of shear flow, and the short fibers are oriented in the direction of travel of the bubbles between the bubble rows. Combined with the fiber orientation effect caused by the collision of the bubbles mentioned above, the fiber orientation in the fiber dispersion liquid becomes even more effective. It will be done.

A molding tank that increases the degree of fiber orientation through the movement of air bubbles]
The fiber dispersion liquid in 0 is subjected to a defoaming action due to the reduced pressure in the vacuum tank] 1, and after being completely defoamed, it is cured and molded under the required heating conditions to form a fiber optic composite material with a high degree of tJAm orientation. becomes.

In Kenpo, which increases the degree of orientation of short fibers in a fiber dispersion liquid by floating air bubbles, the size and type of air bubbles may be in principle as long as they can float in the fiber dispersion liquid. There are no particular restrictions as long as the gas is chemically stable with respect to the degree of orientation, the various materials contained in the fiber dispersion liquid, such as the thickening material and the hardening agent. Furthermore, it is also possible to use liquid bubbles that have a lower specific gravity than the fiber dispersion liquid, are chemically stable, and do not pose obstacles such as diffusion.

Another example of Kempo is shown in FIG. FIG. 4 is a schematic view of the case where short fibers are oriented along the circumferential direction of a hollow tube, and is a sectional view of a molding die placed horizontally at a predetermined inclination.

In the figure, 40 is a molded tube, with an outer tube 42 and an inner tube 43.
It is rotatably placed horizontally at a required angle of inclination. The forming tube 40 is filled with the fiber dispersion liquid prepared in advance, small bubbles a are generated from the lower tube end of the forming tube, and the speed of the bubbles floating in the fiber dispersion liquid is synchronized with the rate of formation heating. The process cures and forms a tubular composite material with circumferentially oriented fibers.

In the above, examples have been described in detail regarding a method for orienting short fibers in the liquid by floating bubbles in the fiber dispersion liquid, which have a specific gravity smaller than that of the fiber dispersion liquid. By moving a large number of large solid particles in the fiber dispersion liquid, the short fibers in the fiber dispersion liquid can be oriented in the moving direction of the solid particles by the same principle as in the case of small bubbles described above. Hereinafter, a method using solid particles having a higher specific gravity than the fiber dispersion liquid will be explained in detail with reference to examples.

FIG. 5 shows a schematic diagram of a method for orienting fibers using solid particles larger than the specific gravity of the fiber dispersion liquid. Figure 6 is Figure 5
FIG. 3 is a main cross-sectional view of the solid particle supply section shown in FIG. In FIG. 5, the solid particles are returned onto the solid particle supply plate 24 by a suitable transfer means such as a first mixing tank, a second mixing bear, or the like.

As described above, by configuring a circuit in which solid particles circulate and moving a large number of solid particles C in the fiber dispersion liquid in the forming tank 10, the short fibers in the fiber dispersion liquid collide with each other as the solid particles move. The length direction of the fibers is aligned in the moving direction (vertical direction) of the solid particles by the action of the couple caused by the movement of the solid particles and the local swirling flow caused by the movement of the solid particles.

The fiber dispersion liquid, in which the degree of fiber orientation has been increased by the movement of the solid particles, is cured and molding is completed in the same manner as in the above embodiment.

FIG. 6 shows an example of the configuration of a supply section for intermittently supplying solid particles into the forming tank, and the solid particles C are sent from the solid particle supply pipe 23 from the groove array 26 of the slope 25 that descends toward the front. ,
Solid grain delivery adjustment plate 27 that slides horizontally in the direction of the arrow
As a result of this operation, the solid particles fall intermittently onto the solid particle supply plate 24 and are supplied into the forming tank 10 along the plurality of rows of grooves provided on the solid particle supply plate 24 .

In the above example, the solid particles were moved vertically in the forming bath by the action of gravity, but the solid particles made of steel were moved in the desired direction by magnetic force, and the fibers were oriented in the desired direction. Composite materials can be molded.

The solid particles used in Kenpo are metal and inorganic.

They are small particles made of organic material, and various particles are selected in consideration of the specific gravity, chemical properties, etc. of the matrix material. Furthermore, in special cases, it is also possible to use solid particles in which a magnetic field is applied to the solid particles themselves in order to control their movement.

Furthermore, in the embodiments described above, the air bubbles and solid particles are guided out of the fiber dispersion liquid after orienting the fibers in a desired direction, which reduces the weight of the composite material to be molded.

Improving insulation properties 9 Materials constituting composite materials in which air bubbles, liquid bubbles, and solid particles after being used to improve the degree of fiber orientation are retained in the fiber dispersion liquid at the required ratio for purposes such as reinforcement. It is also possible to perform curing molding as part of the process.

When the moving body for orienting the short fibers is a solid particle, the shape of the solid particle is preferably a spherical shape that does not change its projected shape in the direction of movement even during rotation during movement in the fiber dispersion liquid.

In addition, the diameter is calculated from the length of the short fiber], /4, considering the frequency of collisions with the short fibers when moving in the fiber dispersion liquid and the effect of the couple that occurs at that time. It is desirable that the size corresponds to the fiber length. Furthermore, it is desirable that the moving speed be higher in terms of the efficiency of increasing the degree of fiber orientation, but on the other hand, when the speed of the solid particles increases, the wake generated behind the solid particles causes disturbance in the fiber arrangement. Grain velocity is limited. For this reason, a specific gravity difference F between the fiber dispersion liquid and the solid particles is preferably in the range of 4 to 10.

In the present invention, bubbles and solid particles are used as moving bodies for fiber orientation, but each moving body has the following characteristics, so even after processing to become a matrix,
There is no need for processing such as washing as in the case of solid particles, etc.
Easy to handle. On the other hand, the force acting on fiber orientation due to air bubbles is mainly due to buoyancy, and the acting force for orientation is smaller than that of solid particles. Further, consideration must be given to the fact that the size of the bubbles changes depending on the depth in the fiber dispersion liquid, and to the bumping that occurs when bubbles are mixed into the fiber dispersion liquid at high temperatures.

A feature of using solid particles for fiber orientation is that a larger acting force can be obtained compared to air bubbles, and Kenpo can also be applied to fiber-dispersed liquids with a large mixing ratio of fibers. In addition, when bubbles move in a fiber dispersion liquid with relatively long fiber length<ta fibers and fiber dispersion is uneven, the speed of the bubbles becomes uneven, resulting in multiple bubbles coalescing. However, in the case of solid particles, this problem does not occur and uniform orientation of the fibers is possible.

Next, an example of molding by the method of the present invention will be explained. The material is glass fiber with a diameter of 19 seconds and a length of 3 mm.
and epoxy resin, methyl ethyl ketone was added as a viscosity modifier (15%) to these materials to prepare a fiber dispersion in which glass fibers were uniformly dispersed, and 10% of a hardening agent was added to this to uniformly disperse the fibers. The stirred liquid is 250m high and 140m wide.

Fill a mold with an inner thickness of 5 cm, and place 1 inch at the bottom of the mold.
Twenty bubbles of about 6 M in size were generated per nozzle from nozzles with an inner diameter α5u arranged at a pitch of 5 cm, and after the fibers were oriented, they were heated and hardened to form a fiber composite board. On the other hand, a plate was molded using the same blending ratio as above and without the orientation treatment using bubbles. A test piece whose length was in the direction of bubble movement was taken from the sample treated with bubbles, and compared with the strength (bending) of a test piece taken from a sample not treated with bubbles. The strength of the former is 5.2Kl/l
d, the latter had an interval of 5.8 -, and the former showed an improvement in strength due to fiber orientation.

As is clear from the detailed description above, according to the method of the present invention, a fiber composite material of excellent quality and with a high degree of orientation of short fibers can be obtained by extremely simple means.

The present invention, which is capable of controlling the arrangement of short fibers within the matrix, can be applied to various types of whiskers that are expected to have a large composite effect as reinforcing agents.
It enables orientation, which was difficult in the past, and contributes to the expansion of its applications.

In addition, it is possible to improve not only the mechanical properties of the composite material but also various composite effects, such as imparting dielectric constant anisotropy through fiber orientation of a material filled with carbon fibers or the like.

[Brief explanation of the drawing]

Figure 1 relates to the principle of the method of the invention, and is a schematic diagram showing the course of fiber orientation due to the floating of air bubbles. Figure 2 shows the degree of fiber orientation in the fiber dispersion liquid to explain the short-am orientation effect in the method of the invention. 3 is a schematic diagram of an apparatus for molding a composite material with a high degree of fiber orientation by the method of the present invention, and FIG. 4 is a method of molding a tube in which fibers are oriented in the circumferential direction based on the present invention. FIG. 5 is a schematic diagram of a molding apparatus that orients fibers in a fiber dispersion liquid by moving solid particles based on the method of the present invention to obtain a composite material with a high degree of fiber orientation. FIG. 3 is a detailed view of the solid particle supply section as abbreviated in FIG. 1...First mixing tank 3...Second mixing tank 7...Bubble nozzle lO...Forming tank 24...Solid particle supply plate Mu...Bubble b...Fiber dispersion liquid C. ...Solid particle diagram 1 Figure 3 -124- Figure 4

Claims (1)

[Claims] 1. In molding a composite material filled with short fibers, a large number of small bubbles are generated in a m-paper dispersion liquid in which short fibers and a matrix are mixed, and the floating of the bubbles causes a couple to the short fibers. 1. A method for arranging fibers of a short fiber optical fiber composite material, characterized in that the length direction of the short fibers is oriented in the direction of movement of air bubbles, thereby increasing the degree of orientation of the short fibers. 2. In molding a composite material filled with short fibers, a large number of solid particles having a specific gravity larger than that of the liquid are placed in a fiber dispersion liquid in which short fibers and a matrix are mixed, and the movement of the solid particles causes the above-mentioned short JijIi# to By applying a couple, the length direction of the short fibers is oriented in the direction of movement of the solid particles,
A fiber arrangement method for short fiber optical fiber composite materials characterized by increasing the degree of orientation of short fibers.