JP3480504B2 - Thermoplastic composite material for molding - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thermoplastic resin composite material for molding which has particularly excellent fracture toughness.

[0002]

2. Description of the Related Art Conventional fiber-reinforced resin composite materials have low interlaminar strength, especially in thermosetting resin composite materials, and have low fracture toughness values such as GIC obtained in a Mode I fracture test and durability as molded articles. The durability and impact resistance are not satisfactory. On the other hand, various fiber-reinforced resin composite materials using a thermoplastic resin as a matrix have been developed. In these composite materials, the fracture toughness value is greatly improved due to the high fracture toughness of the matrix.

[0003]

However, when the thermoplastic resin is used as the matrix, for example, when the prepreg tape-like material in which the resin is impregnated in advance between the reinforcing fibers is laminated and molded, the layers appear clearly. However, interlaminar fracture easily occurs and a high fracture toughness value is not always obtained.

[0004]

The constitution of the present invention for solving the above-mentioned problems is such that the reinforcing fibers are oriented in one direction and impregnated with a thermoplastic resin as a matrix, and the reinforcing fibers have a cross-section in the direction perpendicular to the direction. The average of the continuous fiber bundle boundary length / fiber bundle average major axis length ratio existing on the horizontal line is 2.5 or less, and the minor axis / major axis length ratio of the fiber bundle is 0.1 or more. And a fiber-reinforced thermoplastic resin composite material for molding. It also comprises a molding fiber-reinforced thermoplastic resin composite material having a reinforcing fiber length of 30 to 400 mm.

Examples of the thermoplastic resin used in the present invention include polyamide resins such as nylon 6 and nylon 6.6, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyolefin resins such as polypropylene and polyethylene, and polycarbonate and polyether. Examples thereof include, but are not limited to, imide, polyphenylene sulfide, and polyether ketone. The reinforcing fibers are glass fiber, carbon fiber,
Examples thereof include organic and inorganic fibers such as aramid fiber, but are not limited thereto.

The reinforcing fibers are oriented in one direction and form a fiber bundle, and the fiber bundle has a minor axis / major axis length ratio average of 0.1 or more and is horizontal in a cross section in a direction perpendicular to the reinforcing fibers. It is characterized in that they are arranged so that the average ratio of the continuous boundary length of fiber bundles present on the line / the average major axis length of fiber bundles is 2.5 or less. By arranging the reinforcing fibers in this way, for example, when the fracture toughness value GIC according to mode I is evaluated, it is possible to obtain a high fracture toughness value in which the progress of cracks hardly occurs. If the average ratio of the minor axis / major axis of the fiber bundle is smaller than 0.1, the boundary region of the fiber bundle becomes large and breakage easily occurs, which is not preferable.

Further, when the ratio of the continuous boundary length of fiber bundles / the average major axis of fiber bundles present on the horizontal line in the cross section in the direction perpendicular to the reinforcing fibers is larger than 2.5, the progress of cracks easily occurs and the fracture toughness value is increased. Is decreased, which is not preferable. The average fiber length of the reinforcing fibers is preferably 30 to 400 mm. 30 mm
If the length is shorter, the strengthening efficiency decreases and good mechanical properties cannot be obtained, which is not preferable. Further, if it is longer than 400 mm, it is difficult to shape the mold during molding, which is not preferable.

The method of impregnating and coating the reinforcing fibers with the resin and the method of obtaining a molded article are, for example, a method in which a thermoplastic resin powder is supported between the reinforcing fibers and then heat compression molding is performed, and between the reinforcing fibers. It is possible to use a method in which a thermoplastic resin powder is supported, and then a thermoplastic resin is further coated thereon and heated and compression molded, or a method in which reinforcing fibers and matrix fibers are mixed and then heated and compression molded. . Among them, the mixed fiber method has excellent impregnation characteristics, and more preferably, it is desirable to use the mixed fiber method using the draft spinning.

[0009]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. Example 1 Nylon 6 fibers and carbon fibers are aligned and drawn and spun to make the nylon 6 fibers and carbon fibers mixed and substantially untwisted, and the surface of the yarn corresponds to 5% of the total weight of the yarn. Wound and coated with nylon 6 fiber to obtain a mixed yarn having a total yarn denier of 5800, a carbon fiber volume content of 50%, and an average fiber length of 75 mm.

The mixed fiber obtained as described above is wound around a metal frame while applying a predetermined amount of tension. Then, it was supplied into a 250 mm square fitting mold (a pair of concave side is an opening) installed in a heat press to perform heat compression molding of a unidirectionally strengthened flat plate. In order to provide a preliminary crack on the molded product, a thickness of 10
A Teflon film having a length of μm and a length of 50 mm is inserted into one of the ends at the center of the thickness. The mold temperature and applied pressure are 260 ° C., 10 kg / cm ² and thickness 3 mm, 25
A 0 mm square flat plate was obtained. As a result, the average of the length ratios of the short axis and the long axis of the fiber bundle was 0.35, and the average of the ratio of continuous fiber bundle boundary length / fiber bundle average long axis existing on the horizontal line in the cross section was 0. A molded plate of 0.56 was obtained. The measurement and calculation of these ratios were performed as follows. A molded product obtained by heat compression molding as described above has a width of 10 mm and a length of 20 m.
After cutting out with the longitudinal direction parallel to the fiber orientation direction in m, and embedding the reinforcing fiber direction in the epoxy resin in the vertical direction,
Using a paste containing 0.3 μm alumina powder and a polishing buff, the cross section of the molded product was polished to a mirror-finished state. This sample was used for observation with a reflection type optical microscope, and the minor axis and major axis length of the fiber bundle were also corrected by image-processing the image of the cross section of the molded product by further incorporating the optical microscope image into the image processing device. The continuous fiber bundle boundary length existing on the horizontal line in the cross section was measured. Based on the values obtained, the ratio of the minor axis / major axis of the fiber bundle and the ratio of the continuous boundary length of the fiber bundle / the average major axis of the fiber bundle were calculated.

From the unidirectional reinforcing flat plate obtained as described above, the longitudinal direction is parallel to the reinforcing fibers, the width is 25 mm and the length is 155 m.
Cut out to m. Using this sample, GIc was measured by the fracture toughness evaluation method of Mode I method. The results are listed in Table 1. Fracture between layers was extremely small, and many fractures were observed within the fiber bundle, showing a high GIc value.

Comparative Example 1 Nylon 6 using 3 carbon fibers having a filament number of 12K
A resin was directly impregnated between the fibers to form a tape, and then a unidirectionally reinforced molded article for GIc measurement was obtained in the same manner as in Example 1. In this case, the ratio of the minor axis length / the major axis length of the reinforcing fiber bundle in the cross section in the direction perpendicular to the reinforcing fibers of the obtained molded product was 0.05. The ratio of the continuous boundary length of the fiber bundle / the average major axis length of the fiber bundle existing on the horizontal line in the same section was 3.7. GIc was measured using this molded product. The results are listed in Table 1. The layers between the fiber bundles clearly appeared, and after the measurement, it was clearly recognized that the layers were broken.

[0013]

[Table 1]

[0014]

EFFECTS OF THE INVENTION By subjecting the thermoplastic resin fiber-reinforced composite material for molding of the present invention obtained by arranging reinforcing fibers as described above to molding, a molded article having a high fracture toughness value can be obtained. .

Claims (2)

(57) [Claims] 1. A fiber bundle continuous boundary length / fiber bundle average major axis which is obtained by orienting reinforced fibers in one direction and impregnated with a thermoplastic resin as a matrix, and is present on a horizontal line in a cross section in a direction perpendicular to the reinforced fibers. The average length ratio is 2.5 or less,
A fiber-reinforced thermoplastic resin composite material for molding, characterized in that the fiber bundle has a minor axis / major axis length ratio of 0.1 or more. 2. The fiber-reinforced thermoplastic resin composite material for molding according to claim 1, wherein the reinforcing fibers have an average length of 30 to 400 mm.