JPH0211406B2 - - Google Patents

Description

[Detailed Description of the Invention] One of the methods for manufacturing fiber reinforced plastics (hereinafter referred to as FRP) is to use prepreg, and in the prepreg used for molding FRP,
The orientation direction of the fibers in it is the final product of FRP
It is desirable that the direction of the stress coincides with the direction of the stress generated or applied. In general, so-called unidirectional prepregs in which fiber yarns are aligned in one direction and impregnated with matrix resin, and bidirectional prepregs in which fabrics consisting of warp and weft yarns are made into prepregs, are used. It is appropriately cut and used according to the required reinforcement direction.

A special example of this is bias cross prepreg (hereinafter referred to as bias prepreg). Bias prepreg can be easily obtained, for example, by cutting an ordinary fabric prepreg at an angle of 45° to the longitudinal direction of the fabric as a conventional method.
It is useful in responding to the direction of stress applied to FRP, and another feature of bias prepreg is that it can easily fit onto curved surfaces.
It has a wide range of uses as an intermediate material for FRP.

However, a major drawback of the bias prepreg obtained by the above-described conventional method is that its dimensions are limited.

On the other hand, as a method of obtaining a fabric with threads oriented in the bias direction, infinite length bias cloth can be made by cutting a cylindrical cloth in a spiral shape. The dimension in the width direction is unstable, and it is difficult to make it into a prepreg, and it is extremely difficult to manufacture an infinite length bias prepreg.

The present inventors have conducted various studies on methods of processing cylindrical cloth into bias prepreg, and have arrived at the present invention.

The present invention will be described in detail below with reference to the drawings and examples.

The cylindrical cloth used in manufacturing the bias prepreg of the present invention can be obtained by weaving using a normal weaving machine using a warp and weft diagonal weave, or by using a circular loom.
If the former method is used, the warp density in the selvage part is likely to be different from that in other parts, and sufficient care and condition settings are required in manufacturing it.It is preferable to manufacture cylindrical cloth using a circular loom. Manufacturing is preferred.

By cutting the cylindrical cloth thus obtained at an angle of 45° to the longitudinal direction as shown in Fig. 1A,
A bias cloth with warp and weft oriented at a 45° angle can be obtained. The symbols in the figure are warp threads 2 and weft threads 3 that form the cylindrical cloth 1.

When cutting, the incision angle θ with respect to the longitudinal direction of the fabric is not limited to 45°, and may be set appropriately as necessary, but when isotropic physical properties are required, θ = 45° is usually adopted, so the following 45゜Explain about incision.

A bias cloth can be obtained by cutting a cylindrical cloth into a spiral shape as described above, but the dimensions of this cloth in the length and width directions are undefined, and after cutting, it is impregnated with matrix resin and made into a prepreg like a normal cloth It is impossible to do so.

The present inventors have arrived at the present invention as a result of their studies on how to impregnate matrix resin and incise the cloth using a cylindrical cloth.

The process necessary to obtain a bias prepreg using a cylindrical cloth as a starting material is first to correct the orientation of the warp or weft of the cylindrical cloth. As mentioned above, even when a circular loom is used, the orientation of the weft yarns is disturbed due to uneven density of the warp yarns in the selvedges, and the orientation correction process is unavoidable when winding up the gray fabric.

The second step is to fix the longitudinal and widthwise dimensions of the bias cloth when the cylindrical cloth is cut out. The third step is to impregnate the bias cloth with matrix resin, and the fourth step is to cut it out. There are four processes (in no particular order). It becomes necessary.

In the method of the present invention, the above four processes are:
It is carried out as follows. The details will be explained with reference to FIG.

The cylindrical cloth 1 shown in FIG. 2 is placed over a cylindrical core 4 whose diameter can be adjusted, and the arrangement and density of the warp threads 2 are corrected with the outer diameter of the core slightly smaller than the inner diameter of the cloth. Next, the core body 4 is expanded to the cross inner diameter. At this time, since the weft threads of the cylindrical cloth are irregular, the core body 4 is expanded to the shortest weaving length of the weft threads, that is, the minimum inner diameter of the cylindrical cloth.

In this state, the slack weft yarn is tightened at the incision line 5, and the excess weft yarn is concentrated at the incision line 5.

As the core body 4 for carrying out such operations, a metal cylinder, a plastic cylinder, an inflatable tube, etc., which is divided into two parts, is used. The corrected cylindrical cloth is thus fixed on the core body 4, and then the masking resin is applied to the release paper and attached to the cylindrical cloth 1 on the core body 4.

The release paper coated with matrix resin is indicated by symbol 6 in the figure. The figure shows a state in which the release paper is cut to a predetermined size and then manually pasted onto the cylindrical cloth 1, but it is also possible to wrap a strip of release paper around the cylindrical cloth in a helical pattern.

When a release paper is attached to the cloth 1 with a matrix resin on its surface, the matrix resin does not impregnate into the threads, but the tissue of the cloth 1 is already fixed due to the effect of the release paper, and the incision line 5 Even if the cloth 1 is incised along the steps, its dimensions are fixed, and the desired dimensions and yarn orientation can be obtained.
The matrix resin used in the present invention has tackiness in a normal state, but it is necessary to make it tackiness by heating or adding a solvent, and epoxy resins, phenolic resins, ester resins, etc. are usually used.

In this way, the prepreg precursor 7 is prepared by pasting silicone release paper on the bias cloth with matrix resin.
is obtained.

By repeating the above operations in the longitudinal direction of the cylindrical cloth, a continuous body of prepreg precursor 7 is obtained, which has fixed dimensions and can be easily adapted to an impregnation process such as hot pressing.

A more detailed explanation will be given below based on examples.

Example 1 Carbon fiber yarns having a weight of 0.225 g per 1 m were used to make a bag weave with a reed width of 38 cm using an 8-ply sateen weave with double warp and weft yarns at a density of 10 yarns/cm for both the warp and weft. The average inner diameter of the resulting 8-ply satin bag weave was approximately 25 cm. This cloth had some warp density unevenness at the ears, a change in the inner diameter at the location where the shuttle was replaced, and some sink marks.

This cylindrical cloth is divided into two parts and placed over a core made from a plastic cylinder, and the outer diameter of the core is increased until there is enough room for the warp threads to move (this outer diameter is approximately equal to the minimum inner diameter of the cloth). ) In this state, irregularities in warp density were corrected.

Next, the outer diameter of the core body is increased to the minimum inner diameter of the cloth, and the slack weft threads are collected at the incision line.
Release paper coated with an epoxy resin having a basis weight of 310 g/m ² was attached using the resin as shown in FIG. The incision was approximately 2 cm wide, leaving an area free of resin, and a spiral incision was made at a 45° angle from this area.

The thus obtained prepreg precursor was hot-pressed at 90° C. for 2 minutes to impregnate the resin into the threads, and it was possible to obtain a long bias prepreg with a resin content of about 40% and a width of about 50 cm.

[Brief explanation of drawings]

FIG. 1A illustrates the state in which a cylindrical cloth is cut, and FIG. 1B shows the bias cloth obtained by cutting. FIG. 2 is a diagram illustrating a method of covering a core body with a cylindrical cloth, overlaying a matrix resin together with release paper thereon, and cutting the core body.

Claims (1)

[Claims] 1. In a method for producing bias prepreg by cutting a cylindrical woven fabric in a spiral shape in the longitudinal direction of the fabric, after laminating a release paper having a matrix resin film to the cylindrical fabric, A method for manufacturing a bias prepreg, which comprises cutting a cylindrical fabric in a spiral shape along its longitudinal direction.