JPH06155495A - Bumper beam made of fiber-reinforced thermoplastic resin stampable sheet - Google Patents

Abstract

PURPOSE:To furnish a bumper beam made of a fiber-reinforced thermoplastic resin stampable sheet which has a high mechanical strength in the longitudinal direction and is light in weight. CONSTITUTION:This bumper beam is made of a fiber-reinforced thermoplastic resin stampable sheet in which discontinuous fibers and thermoplastic resin are mixed by a paper making method and in which the discontinuous fibers are orientated in one direction. The fiber-reinforced thermoplastic resin stampable sheet in which the ratio of the discontinuous fibers is 25 to 50wt% and the ratio between a tensile strength in the direction of orientation of the discontinuous fibers and the tensile strength in the direction perpendicular to the direction of the orientation is 1.5 or above is subjected to heat-pressure molding so that the direction of the orientation of the discontinuous fibers be parallel substantially to the longitudinal direction of the bumper beam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bumper beam made of a fiber reinforced thermoplastic resin stampable sheet, and is suitably used as a lightweight automobile bumper beam which requires mechanical strength in one direction.

[0002]

2. Description of the Related Art Conventionally, a metal bumper beam has been used as a protective cushioning component for a resin bumper of an automobile. However, the metal bumper beam requires complicated and complicated work steps such as welding in manufacturing. Further, from the viewpoint of improving the fuel efficiency of automobiles, lighter weight materials have been strongly demanded even more than before, but metal methods have reached the limit of solving such problems. On the other hand, the fiber-reinforced thermoplastic resin stampable sheet produced by the conventional laminating method, papermaking method and dry dispersion method has no difference in strength between the longitudinal direction and the direction perpendicular thereto. Therefore, for a bumper beam that requires high mechanical strength in the longitudinal direction, the strength in the direction perpendicular to the longitudinal direction is satisfied, but the strength in the longitudinal direction cannot satisfy the requirement. Therefore, in order to obtain the required strength, the product weight must be increased. On the other hand, the production of a unidirectional fiber reinforced thermoplastic resin stampable sheet obtained by impregnating a thermoplastic resin into a laminate of reinforced continuous fibers and continuous fiber mats aligned in one direction in JP-A-62-240514. And a method for manufacturing a lightweight bumper beam using the stampable sheet has been proposed. However, the reinforcing long fibers aligned in one direction may bend during molding, or the desired strength may not be exhibited because the reinforcing long fibers aligned in one direction have poor fluidity.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a lightweight fiber reinforced thermoplastic resin stampable sheet bumper beam having high mechanical strength in the longitudinal direction.

[0004]

DISCLOSURE OF THE INVENTION In a bumper beam made of a fiber reinforced thermoplastic resin stampable sheet of the present invention, discontinuous fibers and thermoplastic resin are mixed by a papermaking method, and the discontinuous fibers are oriented in one direction. It is composed of a fiber reinforced thermoplastic resin stampable sheet, and the ratio of the discontinuous fibers in the fiber reinforced thermoplastic resin stampable sheet is 2
The fiber-reinforced thermoplastic resin stampable sheet is 5 to 50% by weight, and the ratio of the tensile strength in the direction in which the discontinuous fibers are oriented and the tensile strength in the direction perpendicular to the orientation direction is 1.5 or more. It is characterized in that it is formed by heating and pressurizing so that the orientation direction of is substantially parallel to the longitudinal direction of the bumper beam.

The fiber-reinforced thermoplastic resin stampable sheet used as a raw material in the present invention is a resin composite material capable of being heat- and pressure-molded in which a thermoplastic resin is impregnated in a discontinuous fiber mat as is well known.

The method for producing a fiber reinforced thermoplastic resin stampable sheet according to the present invention is a sheet in which discontinuous fibers and a thermoplastic resin are mixed in water to form a web by a papermaking method, which is heated, pressurized and cooled. Japanese Patent Publication Sho 52-12
The method described in Japanese Patent Publication No. 283, Japanese Patent Publication No. 55-9119 and the like can be used. Further, as a paper-making method for improving the orientation of the discontinuous fibers, the methods described in JP-A-4-208405, JP-A-4-208406 and JP-A-4-208407 can be mentioned.

In the fiber reinforced thermoplastic resin stampable sheet used in the present invention, the proportion of discontinuous fibers in the thermoplastic resin stampable sheet is 25 to 50.
% By weight, preferably 35 to 42% by weight. When the proportion of the discontinuous fibers is less than 25% by weight, it is difficult to obtain the strength required by the bumper beam, and the resin flow during molding impairs the orientation of the discontinuous fibers, resulting in a decrease in the strength. . Further, when the proportion of discontinuous fibers exceeds 50% by weight, the molding fluidity is remarkably deteriorated, and a high molding pressure is required to prevent wall thinning, so that the molding is limited to a large molding apparatus. In addition, the high pressure causes breakage of the discontinuous fiber and the strength decreases. Further, strength is reduced due to insufficient impregnation of the resin between the discontinuous fibers.

The fiber-reinforced thermoplastic resin stampable sheet used in the present invention has a tensile strength in the direction in which the discontinuous fibers are oriented (JIS K 7113 plastic tensile test method) in a direction perpendicular to the orientation direction. It is unidirectionally reinforced so as to be 1.5 times or more, preferably 1.8 to 4.0 times the length. If the tensile strength of the discontinuous fibers in the oriented direction is lower than 1.5 times the tensile strength in the direction perpendicular to the oriented direction, the required strength in the longitudinal direction of the bumper beam cannot be obtained. In this case, in order to obtain the required strength, it is inevitable that the product weight becomes heavy because the product wall thickness is increased or the proportion of discontinuous fibers is increased.

The discontinuous fibers used in the fiber reinforced thermoplastic resin stampable sheet of the present invention include inorganic fibers such as glass, metal and carbon fibers, or organic fibers. Even if these are used alone, 2 You may use it in combination of 2 or more types. Particularly, glass fibers having a good balance between the reinforcing effect of fibers and economy are preferable. The length of these discontinuous fibers is preferably 6 to 50 mm, particularly 13 to 25 mm. If the length of the discontinuous fiber is shorter than 6 mm, the strength required by the bumper beam cannot be obtained. Further, when the length of the discontinuous fibers exceeds 50 mm, the linearity of the fibers cannot be obtained due to the interference between the discontinuous fibers, and the reinforcing effect of the fibers decreases. Those having the same length may be used alone, or those having different lengths may be used in combination. Further, these fibers may be in the form of single fibers or fiber bundles, and they may be used in combination.

As the thermoplastic resin, polyolefins such as polyethylene and polypropylene, polyvinyl chloride,
Examples thereof include polystyrene, ABS, polyamide, polyester, polycarbonate, polysulfone, modified products thereof, polymer blends, and polymer alloys. Also, a combination of two or more of these may be used. In particular, a highly recyclable polyolefin resin, which is a crystalline resin having a remarkable reinforcing effect by fiber reinforcement and which is suitably used as a material for automobile parts, is preferable. Further, additives, fillers, colorants, foaming agents, cross-linking agents and the like can be added depending on the purpose. These thermoplastic resins are not limited to unused ones,
Scrap or the like may be used, and fibers and fillers may be contained therein.

The bumper beam made of the fiber reinforced thermoplastic resin stampable sheet of the present invention is obtained by heating and melting the thermoplastic resin stampable sheet corresponding to the volume of the bumper beam, and the direction of the discontinuous fiber orientation is the longitudinal direction of the bumper beam. It is placed in a mold so that it is heated and pressed.

[0012]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. Polypropylene was used as the thermoplastic resin, and glass fiber having a fiber length of 13 mm was used as the discontinuous fiber. As the evaluation method, the bumper beam shown in FIG. 1 was molded, and a three-point support compression test was performed under the following test conditions using a compression tester to measure the breaking load. Each test was performed 10 times and the average value was calculated. In addition, from the collision performance in the actual vehicle and the breaking load value in this test, the target of the breaking load value is 5000 kg.
f

Test conditions Load jig: Load jig for pendulum test (US MV
Install the impact ridge of the bumper impact test specified in SS Part 581 in parallel with the bumper beam Test speed: 2 mm / sec Distance between fulcrums: 620 mm

Example 1 A polypropylene stampable sheet produced by a papermaking method and having a glass fiber content of 42% by weight and having a tensile strength ratio of 2.8 in the direction of glass fiber orientation and the direction perpendicular thereto is used. Was molded. As shown in Table 1, it can be seen that the molded product has high strength.

Example 2 A polypropylene stampable sheet having a glass fiber content of 42% by weight produced by a papermaking method and having a tensile strength ratio of 2.2 in the glass fiber orientation direction and its orthogonal direction was used. Was molded. As shown in Table 1, it can be seen that the molded product has high strength.

Example 3 A polypropylene stampable sheet having a glass fiber content rate of 40% by weight produced by a papermaking method and having a ratio of tensile strength in the glass fiber orientation direction to the direction perpendicular thereto is 2.2. Was molded. As shown in Table 1, it can be seen that the molded product has high strength.

Example 4 A polypropylene stampable sheet having a glass fiber content of 40% by weight produced by a papermaking method and having a tensile strength ratio of 2.0 in the orientation direction of the glass fibers and in the direction perpendicular thereto is used. Was molded. As shown in Table 1, it can be seen that the molded product has high strength.

Example 5 A polypropylene stampable sheet produced by a papermaking method and having a glass fiber content of 40% by weight and having a ratio of tensile strength in the glass fiber orientation direction to the direction perpendicular thereto is 1.8. Was molded. As shown in Table 1, it can be seen that the molded product has high strength.

Comparative Example 1 A polypropylene stampable sheet having a glass fiber content of 40% by weight produced by a papermaking method and having a tensile strength ratio of 1.0 in the glass fiber orientation direction and the direction perpendicular thereto is used. Was molded. As shown in Table 1, the strength of the molded product is not satisfactory.

Comparative Example 2 A polypropylene stampable sheet having a glass fiber content of 40% by weight produced by a papermaking method and having a tensile strength ratio of 1.2 in the glass fiber orientation direction and its orthogonal direction was used. Was molded. As shown in Table 1, the strength of the molded product is not satisfactory.

Comparative Example 3 A polypropylene UD stampable sheet having a glass fiber content of 42% by weight, which was produced by a laminating method using continuous glass fibers, was used for molding. As shown in Table 1,
The strength of the molded product is not satisfactory.

Example 6 A polypropylene stampable sheet produced by a papermaking method and having a glass fiber content of 35% by weight and having a tensile strength ratio of 2.5 in the orientation direction of the glass fibers and in the direction perpendicular thereto is used. Was molded. As shown in Table 1, it can be seen that the molded product has high strength.

Example 7 A polypropylene stampable sheet having a glass fiber content of 35% by weight produced by a papermaking method and having a tensile strength ratio of 2.2 in the direction of glass fiber orientation and the direction perpendicular thereto is used. Was molded. As shown in Table 1, it can be seen that the molded product has high strength.

Comparative Example 4 A polypropylene stampable sheet having a glass fiber content of 40% by weight, which was produced by a laminating method using continuous glass fibers, was used for molding. As shown in Table 1, the strength of the molded product is not satisfactory.

Comparative Example 5 The polypropylene stampable sheet used in Example 1 was molded so that the orientation direction of its discontinuous fibers was perpendicular to the longitudinal direction of the bumper beam. As shown in Table 1,
The strength of the molded product is not satisfactory.

[0026]

[Table 1]

[0027]

As described above in detail, the fiber reinforced thermoplastic resin stampable sheet bumper beam of the present invention is a high-performance lightweight bumper beam with improved mechanical strength in the longitudinal direction.

[Brief description of drawings]

FIG. 1 is a schematic view of a bumper beam molded product used in this example.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location // B29K 105: 06 B29L 31:30 4F (72) Inventor Kensuke Ohno 1 Toho-cho, Yokkaichi-shi, Mie Address Mitsubishi Petrochemical Co., Ltd. Yokkaichi Research Institute

Claims (3)

[Claims] 1. A fiber-reinforced thermoplastic resin stampable sheet comprising a fiber-reinforced thermoplastic resin stampable sheet in which discontinuous fibers and a thermoplastic resin are mixed by a papermaking method, and the discontinuous fibers are oriented in one direction. Fiber-reinforced heat in which the proportion of the discontinuous fibers in the interior is 25 to 50% by weight, and the ratio of the tensile strength in the direction in which the discontinuous fibers are oriented and the tensile strength in the direction perpendicular to the orientation direction is 1.5 or more. A bumper beam made of a fiber reinforced thermoplastic resin stampable sheet, characterized in that a thermoplastic resin stampable sheet is formed by heating and pressurizing so that the orientation direction of the discontinuous fibers is substantially parallel to the longitudinal direction of the bumper beam. . 2. The bumper beam made of a fiber reinforced thermoplastic resin stampable sheet according to claim 1, wherein the discontinuous fiber is a glass fiber having a fiber length of 6 to 50 mm. 3. The bumper beam made of a fiber reinforced thermoplastic resin stampable sheet according to claim 1, wherein the thermoplastic resin is a polyolefin resin.