JPH06344837A - Bumper beam made of stampable sheet - Google Patents

Abstract

PURPOSE:To provide a light-weight bumper beam made of stampable sheet, which has high mechanical strength, by using fiber reinforced thermoplastic resin. CONSTITUTION:A bumper beam is formed by compressing a stampable sheet manufactured by the combination of non-continuous fiber and thermoplastic resin. A bumper beam made of the stampable sheet, which includes 25-50weight% of non-continuous fiber, is formed so as to have a vertical cross section, which satisfies the condition that section modulus of compression side/ section modulus of pulling side exists in a range from 0.8 to less than 1.5, at a central part in the longitudinal direction, and has high strength. Consequently, the mechanical strength is improved, and a light-weight bumper beam having a high characteristic, in which the reinforcement by design of product is reduced, is provided to reduce the weight of an automobile.

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 stampable sheet using a fiber reinforced thermoplastic resin, which is preferably used as a bumper beam for automobiles which is required to have high mechanical strength and light weight. .

[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. In contrast,
Japanese Patent Application Laid-Open No. 62-240514 discloses the production of a unidirectional fiber reinforced thermoplastic resin stampable sheet in which a thermoplastic resin is impregnated in a laminate of reinforcing filaments and continuous fiber mats aligned in one direction, and the stamper. A method for manufacturing a lightweight bumper beam using a bull seat has been proposed, and the stamper sheet bumper beam manufactured by this laminating method is mounted on many automobiles. However, the stampable sheet produced by the laminating method exhibits excellent characteristics with respect to the tensile stress in the longitudinal direction, but does not exhibit the characteristic as much as the tensile stress with respect to the compressive stress. This is because the thermoplastic resin is not sufficiently impregnated between the reinforcing long fibers aligned in one direction, so that the adhesive strength thereof is low. Therefore, the sectional shape of the bumper beam is designed to be reinforced against the stress on the compression side, and the weight of the reinforced thickness is increased.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lightweight stampable sheet bumper beam using a fiber reinforced thermoplastic resin and having high mechanical strength.

[0004]

A bumper beam made of a stampable sheet according to the present invention is formed by compression-molding a fiber reinforced thermoplastic resin stampable sheet produced by a papermaking method using discontinuous fibers and a thermoplastic resin. In the bumper beam, the proportion of the discontinuous fibers in the fiber-reinforced thermoplastic resin stampable sheet is 25 to 50% by weight, and the section modulus on the compression side in the vertical cross-sectional shape of the central portion with respect to the longitudinal direction of the bumper beam / The cross-sectional modulus on the tensile side is 0.8 or more and less than 1.5.

The section modulus used here can be obtained by the following equation. Z = I / ym Z: Section modulus I: Second moment of area ym: Distance from neutral axis

Next, description will be made with reference to the drawings. Figure 1
When an external force F acts on the bumper beam of, the bumper beam is bent by receiving a bending moment. At this time, the B-side of the beam shrinks and the flange C-side extends, so that compressive stress is generated on the B-side and tensile stress is generated on the flange C. In this case, there is a surface that neither stretches nor shrinks,
That plane is called the neutral plane. The line of intersection between this neutral plane and the cross section of the bumper beam is called the neutral axis. The second moment of area is an amount used to represent the bending rigidity of plates, beams, etc., and its definition and calculation method are described in detail in the literature on material mechanics and the like. When an external force acts on the bumper beam, compressive stress and tensile stress are generated, so that the second moment of area, that is, the section modulus exists on the compression side and the tension side. The value is calculated by determining the dimensions of each part of the bumper beam. Therefore, by changing the thickness and width of the B surface and the thickness and width of the flange C, it is possible to change the section modulus on the compression side / section modulus on the tension side. Also,
The sectional modulus at this time is obtained from the sectional shape in the vertical direction of the central portion in the longitudinal direction of the bumper beam as shown in FIG. At this time, the cross-sectional shape in the vertical direction other than the central portion with respect to the longitudinal direction of the bumper beam also needs to conform to the central portion. However, since the shape of the mounting portion of the bumper beam is restricted depending on the mounting method, its sectional shape does not necessarily have to conform to the sectional shape of the central portion in the longitudinal direction.

The fiber-reinforced thermoplastic resin stampable sheet used as a raw material in the present invention is a compression-moldable resin composite material in which a thermoplastic resin is dispersed in a discontinuous fiber mat as is well known.

As the method for producing the fiber reinforced thermoplastic resin stampable sheet in the present invention, the discontinuous fibers and the thermoplastic resin are mixed in water to form a web by a papermaking method,
This is heated, pressurized and cooled to form a sheet.
The methods described in JP-A-12283, JP-B-55-9119 and the like can be mentioned. Further, as a papermaking method for enhancing the orientation of the discontinuous fibers and orienting the discontinuous fibers in one direction, JP-A-4-208405 and JP-A-4-208 are known.
Methods described in JP-A No. 406 and JP-A No. 4-208407 can be used.

The fiber-reinforced thermoplastic resin stampable sheet produced in this manner has well-balanced mechanical physical properties in which tensile strength and compressive strength are about the same. This is because the thermoplastic resin is sufficiently impregnated between the discontinuous fibers.

The fiber-reinforced thermoplastic resin stampable sheet used in the present invention contains 25 to 50% by weight, preferably 35 to 42% by weight of discontinuous fibers in the stampable sheet. . When the proportion of discontinuous fibers is less than 25% by weight, it is difficult to obtain the strength required by the bumper beam. 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 bumper beam according to the present invention has a cross-sectional shape in which the compression-side section coefficient / the tension-side section coefficient is 0.8 or more and less than 1.5. When the compression-side section modulus / tensile-side section modulus is less than 0.8, the width and thickness of the flange portion where tensile stress is generated when the bumper beam is loaded becomes large, so the space occupied by the bumper beam becomes large. It is unsuitable as a design because it becomes unnecessarily large and it is difficult to attach it to the vehicle body. Further, when the compression-side section modulus / the tension-side section modulus is 1.5 or more, the fiber-reinforced thermoplastic resin stampable sheet used in the present invention is increased in weight and tensile strength due to unnecessary reinforcement on the compression side. The strength of the bumper beam is reduced due to insufficient strength.

Examples of 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, organic fibers and the like. 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. When the length of the discontinuous fiber is shorter than 6 mm, it is difficult to obtain the strength required by the bumper beam. 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.

Examples of the thermoplastic resin include 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 fiber reinforced thermoplastic resin stampable sheet made bumper beam of the present invention is manufactured by heating and melting a fiber reinforced thermoplastic resin stampable sheet corresponding to the volume of the bumper beam, laminating it, and then compression molding. .

[0015]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. A glass fiber having a fiber length of 13 mm was used as the discontinuous fiber, and polypropylene was used as the thermoplastic resin. The evaluation method was as follows. A bumper beam having different compression-side section modulus / tensile-side section coefficient was formed, 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 or more, and the average value was calculated.

Test conditions Load jig: Install the impact ridge of the bumper impact test specified in US MVSS Part 581 in parallel with the bumper beam Test speed: 2 mm / sec

Example 1 A polypropylene stampable sheet having a glass fiber content of 40% by weight manufactured by a papermaking method, and having a vertical cross-sectional shape (see FIG. 2) of a central portion with respect to a longitudinal direction of a bumper beam, a B surface. Width W ₁ is 80mm, flange width W
₂ is 22 mm, height H is 64 mm, B-side thickness t ₁ is 6 mm,
A bumper beam having a side surface thickness t ₂ of 6 mm, a flange C thickness t ₃ of 8 mm, a compression-side section modulus / pulling-side section coefficient of 1.22, and a sectional area of 14.3 cm ² was formed. 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 40% by weight produced by a papermaking method, and having a width W _{1 of} B side in a vertical sectional shape of a central portion with respect to a longitudinal direction of a bumper beam. 80mm, flange width W ₂ is 22m
m, height H is 64 mm, B-side thickness t ₁ is 8 mm, side face thickness t ₂ is 6 mm, flange C thickness t ₃ is 8 mm, and compression-side section modulus / tensile-side section modulus is 1.39. Sectional area is 1
A 5.7 cm ² bumper beam 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 of 40% by weight produced by a papermaking method and having a width W ₁ of the B surface in a vertical sectional shape of a central portion with respect to a longitudinal direction of a bumper beam. 100mm, flange width W ₂ is 14
mm and 20 mm, height H is 100 mm, B-side thickness t ₁ is 6 m
m, side surface thickness t ₂ is 4 mm, and flange C thickness t ₃ is 1
Sectional modulus on compression side / section modulus on tensile side is 1.4 at 0 mm
2. A bumper beam having a cross-sectional area of 16.1 cm ² was formed. 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 width W _{1 of} B side in a vertical sectional shape of a central portion with respect to a longitudinal direction of a bumper beam. 114mm, flange width W ₂ is 21
mm and 30 mm, height H is 96 mm, B-side thickness t ₁ is 12 m
m, the thickness t _{2 of} the side surface is 6 mm to 12 mm, the thickness t _{3 of the} flange C is 18 mm and 12 mm, and the sectional modulus on the compression side / the sectional modulus on the tensile side is 1.32 and the bumper beam has a sectional area of 32.9 cm ^2. Molded. As shown in Table 1, it can be seen that the molded product has high strength.

Comparative Example 1 Glass fiber content by the laminating method 42% by weight
Of the polypropylene stampable sheet, the width W ₁ of the B-side is 80 mm and the width W _{2 of} the flange is 2 in the vertical cross-sectional shape of the central portion in the longitudinal direction of the bumper beam.
2 mm, height H is 64 mm, B-side thickness t ₁ is 6 mm, side face thickness t ₂ is 6 mm, flange C thickness t ₃ is 8 mm, and compression-side section modulus / tensile-side section modulus is 1.22, Sectional area is 1
A bumper beam of 4.3 cm ² was formed. As shown in Table 1, the strength of the molded product is not satisfactory.

Comparative Example 2 Content of glass fiber produced by laminating method: 42% by weight
Of the polypropylene stampable sheet, the width W ₁ of the B-side is 80 mm and the width W _{2 of} the flange is 2 in the vertical cross-sectional shape of the central portion in the longitudinal direction of the bumper beam.
2 mm, height H is 64 mm, B-side thickness t ₁ is 8 mm, side face thickness t ₂ is 6 mm, flange C thickness t ₃ is 8 mm, and compression-side section modulus / tensile-side section modulus is 1.39. Sectional area is 1
A 5.7 cm ² bumper beam was molded. As shown in Table 1, the strength of the molded product is not satisfactory.

Comparative Example 3 Glass fiber content by the laminating method 42% by weight
In the polypropylene stampable sheet, the width W ₁ of the B surface is 80 mm and the width W _{2 of} the flange is 1 in the vertical cross-sectional shape of the central portion in the longitudinal direction of the bumper beam.
6 mm, height H is 64 mm, B-side thickness t ₁ is 8 mm, side face thickness t ₂ is 6 mm, flange C thickness t ₃ is 8 mm, and compression-side section modulus / tensile-side section modulus is 1.58. Sectional area is 1
A 4.7 cm ² bumper beam was molded. As shown in Table 1, the strength of the molded product is not satisfactory.

Comparative Example 4 Content of glass fiber produced by laminating method: 42% by weight
In the polypropylene stampable sheet, the width W ₁ of the B side is 100 mm, the width W _{2 of} the flange is 14 mm and 20 mm, and the height H is 100 mm in the vertical cross-sectional shape of the central portion in the longitudinal direction of the bumper beam. The thickness t _{1 of the} surface is 6 mm, the thickness t _{2 of} the side surface is 4 mm, the thickness t _{3 of the} flange C is 10 mm, and the section modulus on compression side / section modulus on tension side is 1.4.
2. A bumper beam having a cross-sectional area of 16.1 cm ² was formed. As shown in Table 1, the strength of the molded product is not satisfactory.

Comparative Example 5 Content of glass fiber produced by laminating method 42% by weight
In the polypropylene stampable sheet, the width W ₁ of the B side is 114 mm, the widths W _{2 of} the flanges are 21 mm and 30 mm, and the height H is 96 mm in the vertical sectional shape of the central portion in the longitudinal direction of the bumper beam. The surface thickness t ₁ is 1
2 mm, the thickness t ₂ sides 6 mm to 12 mm, section modulus / tensile modulus of section side 1.32 compression side with a thickness t ₃ is 18mm and 12mm flange C, and the cross-sectional area of the bumper beam of 32.9Cm ² Molded. As shown in Table 1, the strength of the molded product is not satisfactory.

Comparative Example 6 A polypropylene stampable sheet having a glass fiber content of 40% by weight manufactured by a papermaking method, and having a width W ₁ of the B surface in a vertical sectional shape of the central portion in the longitudinal direction of the bumper beam. 80mm, flange width W ₂ is 10m
m, height H is 64 mm, B-side thickness t ₁ is 8 mm, side face thickness t ₂ is 6 mm, flange C thickness t ₃ is 8 mm, and compression-side section modulus / tensile-side section modulus is 1.86, Sectional area is 1
A bumper beam of 4.2 cm ² was formed. As shown in Table 1, the strength of the molded product is not satisfactory.

[0027]

[Table 1]

[0028]

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

[Brief description of drawings]

FIG. 1 is a schematic view of a U-shaped molded product imitating a bumper beam and a direction of an external force.

FIG. 2 is a schematic view of a vertical cross-sectional shape of a central portion of the molded product of FIG.

[Explanation of symbols]

B Surface receiving external force (side where compressive stress is generated) C Flange of molded product (side where tensile stress is generated) W ₁ Width of B surface W ₂ Width of flange H Height t ₁ Thickness of B surface t ₂ Thickness of side surface t ₃ Flange thickness

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Goto 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Petrochemical Co., Ltd. Yokkaichi Research Institute

Claims (3)

[Claims] 1. A bumper beam obtained by compression-molding a fiber-reinforced thermoplastic resin stampable sheet produced by a papermaking method using discontinuous fibers and a thermoplastic resin, in the fiber-reinforced thermoplastic resin stampable sheet. The proportion of the discontinuous fibers is 25 to 50% by weight, and the sectional shape of the central portion in the vertical direction in the longitudinal direction of the bumper beam,
The cross-sectional modulus on the compression side / the cross-sectional modulus on the tensile side is 0.8 or more.
A bumper beam made of a stampable sheet, which is less than 5. 2. The stampable sheet bumper beam according to claim 1, wherein the discontinuous fibers are glass fibers having a fiber length of 6 to 50 mm. 3. The stampable sheet bumper beam according to claim 1, wherein the thermoplastic resin is a polyolefin resin.