JPH0657519B2 - Strength member for bumper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of use) The present invention relates to an improvement in a strength member for a bumper.

(Prior Art and Problems Thereof) In recent years, as a bumper for an automobile, a lightweight plastic bumper has been provided. Generally, as shown in FIG. 1, a skin member 1 and a foam cushion which is an energy absorber. It comprises a member 2 and a strength member 3 which is a rigid support member. In particular, the strength member 3 is made of glass fiber reinforced plastic (FRP) as a lightweight and highly rigid material. As such a glass fiber reinforced plastic, SMC (sheet mold compound) having uniform tensile strength in all directions by randomly dispersing short strands of glass fibers (random material) between the upper and lower resins from the glass fiber structure side is used. When used, since the strength of the strength member in the longitudinal direction is insufficient, glass fibers (unidirectional material) continuous in the longitudinal direction of the reinforcing member as SMC are alternated with the random material as shown in JP-B-51-48667. It is recommended to use the one arranged at. However, when a collision load is applied to a bumper using a strength member provided with this kind of unidirectional material, cracks tend to occur on the matrix resin side, and there is a limit to improvement of energy absorption performance.

On the other hand, from the resin surface for the matrix, a glass fiber reinforced unsaturated polyester resin composition that is a combination of an unsaturated polyester resin and glass fibers used in boats and the like requires high impact resistance like a strength member for bumpers. Since it is insufficient for use, unsaturated polyester resin with a relatively high molecular weight is used, unsaturated polyester resin with excellent flexibility and toughness is used, and glass fiber as a reinforcing material is often used. Has been proposed,
According to US Pat. No. 4,064, the impact resistance is not sufficient.
No. 7,845 and No. 4,327,145 presently propose the use of urethane-modified unsaturated polyester resin.

(Problems to be solved by the invention) However, although the above improvement is due to the interaction between the glass fiber and the matrix resin in the glass fiber reinforced plastic, only one of the glass fiber and the matrix resin is focused on, so There is a problem that the crack caused by the interaction is insufficiently considered.
In view of the above, the present invention focuses on the interaction between the two and aims to improve cracking when glass fiber reinforced thermosetting plastic is used as a bumper strength member, and to improve energy absorption performance.

(Means for Solving the Problem) In the present invention, in the strength member made of glass fiber reinforced thermosetting plastic, when the relationship with energy absorption is examined, when a crack occurs in the matrix resin, a notch effect (notch effect) It was found that the improvement of the elongation rate of the matrix resin and the retention of the characteristics of the matrix until the glass fiber is broken are the most effective in improving the energy absorption performance, because the glass fiber easily breaks. As a result, it was completed, and the main point is to manufacture it by SMC method from glass fiber reinforced thermosetting plastic consisting of glass fiber as reinforcing material and thermosetting resin as matrix for dispersing it inside In the strength member for bumper to be used, the thermosetting resin for matrix that is composite with glass fiber is Urethane modified by polyisocyanate compound, an unsaturated polyester resin is adjusted to elongation 4-30%, in the bumper strength member for the elongation being greater than the glass fibers.

In the present invention, the glass fiber used for the strength member is usually used as a strand which is a bundle of fibers. Since the elongation rate of the fiber is about 4%, the elongation rate of the matrix resin when cured is set to 4 to 30%. This is because if the elongation percentage of the matrix resin is less than 4%, the matrix resin is ruptured before the rupture of the glass fiber, and a sufficient synergistic effect cannot be exhibited.

On the other hand, if the elongation percentage of the matrix resin exceeds 30%, the degree of bonding with the glass fibers becomes weak, the Young's modulus decreases, and the rigidity required as a strength member cannot be obtained. Particularly, in relation to the physical properties of other strength members, it is 7-1.
0% is preferable.

As the matrix resin, an unsaturated polyester resin modified with urethane, that is, a urethane modified unsaturated polyester resin obtained by polymerizing the unsaturated polyester resin at the same time as the urethane formation reaction of the polyisocyanate compound or after the polymerization, for example, urethane modified Unsaturated polyester resin "AGU-2100" (manufactured by AG International Chemical Co., Ltd.) can be used, and vinyl ester resin can also be mentioned as a typical example of the resin which can be adjusted to the above elongation rate.

In producing the urethane-modified unsaturated polyester resin, the unsaturated polyester is a liquid at room temperature obtained by mutually dissolving the unsaturated vinyl with a polymerizable vinyl monomer and a polymerization inhibitor, if necessary, in the presence of a polyhydric alcohol. After uniformly mixing the unsaturated polyester resin, the polyisocyanate compound which is liquid at room temperature, and the thermal decomposition type radical polymerization initiator, it is preferable to increase the viscosity (so-called B stage) by carrying out a urethanization reaction in advance. This makes it possible to produce a sheet-shaped or lump-shaped molding material that is free from stickiness and has excellent fluidity during molding. When this molding material is subjected to radical polymerization reaction by hot press molding, its elongation can be adjusted to a predetermined value depending on the degree of transformation of urethane. Further, the liquid unsaturated polyester resin and the polyisocyanate compound which is liquid at room temperature are uniformly mixed and injected into a mold maintained at a predetermined temperature so that the urethanization reaction and the radical polymerization reaction are performed almost at the same time. Good to do.

As the glass fiber, chopped strands cut into about 1 inch are used and randomly packed as shown in FIG. 4 (hereinafter referred to as X type), or in one direction continuous with the chopped strands in one direction. It is also possible to combine them with a flexible strand and alternately arrange them as shown in FIG. 5 (hereinafter referred to as Y type). In the former case, it is appropriate to add 50 to 70% by weight of the above-mentioned molded product. In the latter case as well, 50 to 70% by weight of the weight of the molded product is compounded as a whole, but 70 to 90% by weight of chopped strands and 10 to 10% of unidirectional fibers remain.
It is suitable to add 30% by weight.

As these glass fibers, those manufactured by Asahi Fiber Glass Co., Ltd. can be used.

The above-mentioned strength member has an open cross-section type (hereinafter referred to as A type) as shown in FIGS. 6 and 7, and a closed cross-section type having a closed back surface shown in FIGS. 8 and 9 (hereinafter, B type).
Type), and as shown in FIG. 3, the present invention can also be applied to a case where a bumper B made of only a strength member is attached to a bumper stay S.

(Operation) According to the present invention, since the resin forming the matrix of the glass fiber does not break until the glass fiber breaks, the FRP-specific resin that can withstand a large collision load due to the synergistic action of the glass fiber and the matrix resin It can exhibit energy absorption performance.

Hereinafter, the present invention will be described in detail based on specific examples shown in the accompanying drawings.

(Embodiment) FIG. 1 is a plan view showing an outline of a bumper to which the present invention is applied, and FIG. 2 is a vertical sectional view thereof, in which a cushioning material 2 such as urethane foam is provided inside a skin member 1. A strength member 3 is provided by abutting against the cushioning material 2 after fitting or filling, and is attached to a body (not shown) via a stay 4.

The strength member 3 was manufactured by the following SMC method.

Manufacturing Method of Strength Member (Example 1) 1348 parts by weight of isophthalic acid (hereinafter, simply referred to as “part”), 1657 parts of neopentyl glycol and 988 parts of ethylene glycol were charged into a reactor, and stirring and heating were started while flowing a nitrogen gas. The temperature rises gradually and the maximum temperature is 205 ℃
Then, the dehydration condensation reaction was carried out according to a conventional method, heating was stopped when the acid value of the reaction mixture reached 4.7, the mixture was cooled to 120 ° C., 1884 parts of fumaric acid was charged, and then heating was started again. , The dehydration condensation reaction is performed at the maximum temperature of 225 ° C,
An unsaturated polyester is obtained. Then, the mixture is cooled to 170 ° C., 12 parts of hydroquinone and 2.5 parts of parabenzoquinone are added and dissolved in styrene to obtain an unsaturated polyester resin. After 350 parts of this unsaturated polyester resin was uniformly mixed with 148 parts of polyethylene glycol and 5 parts of t-butyl perbenzoate, polyisocyanate compound 2
07 parts were added and rapidly mixed to obtain a matrix resin having an elongation rate of 7% when cured. 190 parts of 1-inch-long chopped strands are uniformly impregnated into 100 parts of this matrix resin by a conventional method to form a sheet and aged to obtain tack-free SMC. This is cut into a predetermined size, weighed, charged into a heated mold, pressurized and cured, and then demolded to obtain a strength member. Further, in the same manner as in Example 1 above, the elongation rate of the matrix resin is adjusted by modifying the unsaturated polyester resin with urethane,
The physical properties are shown in Table 1.

(Example 2) 1 to 100 parts of the matrix resin used in Example 1
As shown in FIG. 5, 146 parts of inch-length chopped strands and 44 parts of unidirectional strands are uniformly impregnated so as to be arranged alternately, and then sheet-shaped and aged to obtain SMC in a tack-free state. This is cut into a predetermined size, weighed, charged into a heated mold, pressurized and cured, and then demolded to obtain a strength member.

(Comparative Example) Isophthalic acid 184 was used by using the same reactor as in the above example.
6 parts, 1635 parts of maleic anhydride and 2220 parts of propylene glycol are reacted in the same manner as in the above-mentioned example to synthesize an unsaturated polyester having an acid value of 25.5 and then dissolved with styrene to obtain an unsaturated polyester resin. . 3500 parts of this unsaturated polyester resin was mixed with 10 parts of zinc stearate.
A matrix resin having an elongation of 2% is obtained in the same manner as in the example except that the content of the resin is changed to 5 parts, 70 parts of magnesium oxide and 35 parts of t-butyl perbenzoate.

To 100 parts of this matrix resin, 150 parts of 1 inch long chopped strands are uniformly impregnated by a conventional method to form a sheet, aged, and tack-free SMC.
To get This is cut into a predetermined size, weighed, charged into a heated mold, pressurized and cured, and then demolded to obtain a strength member.

Comparative Example 2 1 to 100 parts of the matrix resin used in Comparative Example 1
113 parts of chopped strands and 37 parts of unidirectional strands each having an inch length are uniformly impregnated by a conventional method to form a sheet and aged to obtain SMC in a tack-free state. This is cut into a predetermined size, weighed, charged into a heated mold, pressurized and cured, and then demolded to obtain a strength member.

(Static load test) An open cross-section strength member (AX) of Example 1 and an open cross-section strength member (AY) of Example 2 using a matrix resin having an elongation rate of 7% were used. The static load test was performed on the open cross-section strength member (A-X) of Comparative Example 1 and the open cross-section strength member (A-Y) of Comparative Example 2 used as follows, and the deflection amount and the generated load were compared. The relationships were compared.

Test method As shown in FIGS. 15 (a) and 15 (b), assembly is performed.

The strength member 3 is fixed to the receiving jig 5 by bolting.

Unillustrated tester (Shimadzu Autograph AG-
The jig is set on a pedestal of 10 TA).

A pressing jig 7 is set on the central portion of the strength member 3 via a hard rubber 6 of 200 × 100 × 10 mm.

Adjust 0 point with no load.

Start pressurization → Record the load / deflection continuously.

Stop the pressurization at the breaking point.

The result is shown in FIG. In the case where the chopped strands and the unidirectional strands of Comparative Example 2 were alternately arranged, resin cracks occurred and the strands broke when the amount exceeded about 3.5 tons. On the other hand, in the case of the second embodiment, about 6 to
Sufficiently endured up to n, and when 6.5 ton was exceeded, the resin broke and the strand broke. On the other hand, in the case of Comparative Example 1, since only chopped strands were used, the generated load did not exceed 2 tons, the resin started to break at a deflection amount of around 20 mm, and then the strand also broke. In contrast,
In the case of Example 1, the generated load is smaller than in Example 2, but
It is found that when the unidirectional strand of Comparative Example 2 is larger than that of the unidirectional strand and the elongation percentage of the matrix resin is larger than that of the glass fiber, it is possible to increase the deflection amount of the strength member and to withstand a large load. . The following breaking load and absorbed energy can be read from the above change and its area.

(Relationship between elongation rate of matrix resin and bending strength and tensile strength) Unsaturated polyester resin is modified with urethane to have an elongation rate of 2 to
Change in resin elongation and bending strength and tensile strength of a casting plate made only of matrix resin adjusted to 25% and an SMC plate in which the matrix resin is impregnated with chopped strands at 65% by weight of the molded product are measured according to JIS K7054. And 7055. The results are shown in Fig. 11.

Bending strength and tensile strength decrease according to the resin elongation in the case of cast plate, but resin elongation 5 in the case of SMC plate.
% Rose sharply and remained almost unchanged thereafter.

(Relationship Between Matrix Resin Elongation Rate and Bending Elastic Modulus and Tensile Elastic Modulus) Unsaturated polyester resin is modified with urethane to have an elongation rate of 2 to
Changes in resin elongation and flexural modulus and tensile modulus between a cast plate made only of matrix resin adjusted to 25% and an SMC plate in which the matrix resin is impregnated with chopped strands at 65% by weight of the molded product. JISK705
4 and 7055. Results are shown in FIG.

In the case of a casting plate, the flexural modulus and tensile modulus decrease according to the elongation of the resin, but in the case of the SMC plate, the resin elongation increases sharply up to 5% and the maximum elastic modulus around 7%. You can see that you can get it.

(Bundurum test) Unsaturated polyester resin is modified with urethane to have an elongation of 4 ~
A strength member (B-X type) manufactured from an SMC plate in which a matrix resin adjusted to 50% is impregnated with chopped strands in an amount equivalent to 65% by weight of the molded product as shown in FIG.
And a chopped strand and a unidirectional strand impregnated in an amount equivalent to 65% by weight of the molded product as shown in FIG.
Regarding the strength member (BY type) manufactured from the C plate, the relationship between the matrix resin elongation and the clear striking speed during the pendulum test was investigated, and the results were as shown in FIGS. 13 and 14.

The test conditions are as shown in FIG. 16 and FIG.
The above-mentioned strength member 3 is attached to an automobile having a body weight of 1300 kg, a pendulum of the same weight is set so as to hit the strength member 3 at the lowermost position, and the pendulum is released from a predetermined height by releasing the brakes and gears of the vehicle body. To drop. From the above results, when the elongation rate of the matrix resin exceeds the elongation rate of the glass fiber, the bending strength and the tensile strength decrease, but the NG line where cracks occur in the strength member and the OK line without abnormality increase, and the matrix resin The highest value was obtained at an elongation rate of 7%.

(Effects of the Invention) As is apparent from the above description, according to the present invention, in the plastic bumper, the strength member is made of glass fiber reinforced thermosetting plastic, and the matrix resin to be combined with the glass fiber is made of glass fiber. Since it has been adjusted to a large elongation rate, the resin forming the matrix of this glass fiber does not break until the glass fiber breaks, and the energy specific to FRP that can withstand a large collision load due to the synergistic action of the glass fiber and the matrix resin. It can exhibit absorption performance. Further, since it is only necessary to adjust the elongation rate of the matrix resin, the production is easy.

Although the present invention has been described based on the plastic bumper including the skin member, the foam cushioning member and the strength member shown in FIG. 1, the bumper B including only the strength member shown in FIG. Of course, it can also be applied to mounting.

[Brief description of drawings]

FIG. 1 is a plan view showing an outline of a bumper to which the present invention is applied, FIG. 2 is a vertical cross-sectional view thereof, and FIG. 3 is a vertical cross-sectional view of another bumper to which the present invention is applied. FIG. 5 is a schematic sectional view of a matrix resin in which chopped strands are randomly oriented, FIG. 5 is a schematic sectional view of a matrix resin in which chopped strands and continuous strands are alternately arranged, and FIG. FIG. 7 is a perspective view of a strength member of an open section type, FIG. 7 is a perspective view of a center section of FIG. 6, FIG. 8 is a perspective view of a strength member of a closed section type, and FIG. 9 is a center section of FIG. FIG. 10 is a perspective view, FIG. 10 is a graph showing the relationship between the amount of deflection of the strength member and the generated load in a static load test, FIG. 11 is a graph showing the relationship between resin elongation and bending strength and tensile strength, and FIG. Is the resin elongation, flexural modulus and tensile Graph showing the relationship between sex ratio, first
FIGS. 3 and 14 are graphs showing the relationship between the resin elongation rate of the members having closed cross-section strength and the clear impact speed during the pendulum test, and FIGS. 15 (a) and 15 (b) are front views showing the static load test device. FIG. 16 is an explanatory view showing the outline of the pendulum test, and FIG. 17 is a detailed view of the impact position. 1 ... skin member, 2 ... foam cushioning material 3 ... strength member

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B29L 31:30 4F

Claims (3)

[Claims] 1. A bumper strength member manufactured by an SMC method from a glass fiber reinforced thermosetting plastic, which comprises glass fiber as a reinforcing material and a thermosetting resin as a matrix in which the glass fiber is dispersed. Thermosetting resin for matrix that is composite with fiber is urethane modified by polyisocyanate compound, and elongation is 4
A strength member for a bumper, which is an unsaturated polyester resin adjusted to -30% and has an elongation rate larger than that of glass fiber. 2. The bumper strength member according to claim 1, wherein the glass fibers are chopped strands, and 50 to 70 wt% of the weight of the molded product is randomly filled in the matrix resin. 3. The glass fiber comprises chopped strands and unidirectional strands, and has a weight of 50 to 7 by weight.
The bumper strength as set forth in claim 1, wherein the matrix resin contains 0 wt% of the chopped strands, and 70-90 wt% of the chopped strands and 10-30 wt% of the unidirectional strands are alternately filled. Element.