JPH0757820B2 - Fiber reinforced resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fiber-reinforced resin composition having excellent rigidity, strength and fatigue durability, and in particular, a chopped strand composed of plural kinds of fibers in a resin component. The present invention relates to a fiber-reinforced resin composition that is finely dispersed in.

[Prior Art] A predetermined number of glass fibers (usually 200 to 400)
A sheet reinforced by cutting the bundled glass fiber strands into a predetermined length (usually 1 inch), dispersing them in a resin component such as thermosetting resin, and impregnating the resin component.
The molding compound (SMC) is generally called G-SMC, and the inorganic fiber having a higher elastic modulus than glass fiber, for example, SMC using carbon fiber is generally called C-SMC.

Of these, G-SMC, which uses glass fiber as the original fiber, is (i) sheet-shaped, has no tackiness, is easy to handle, and has high productivity. SMC is solid, easy to cut and weigh, and it is possible to automate molding. (Ii) When molding, there is little decrease in viscosity in the mold, and the glass reinforcement can spread evenly even in complicated shapes,
Molded products with excellent physical properties can be obtained, and thickness changes, ribs, bosses, etc. can also be molded. In addition, it has various features such as excellent surface gloss and less protrusion of glass fibers. In addition, C-SMC uses high-strength and highly elastic carbon fibers for structural materials. ("Carbon fiber" (Ohm)
P13-P15 (Published February 20, 1984); "Reinforced Plastic Handbook" (Nikkan Kogyo Shimbun) P90-P92, P105-
Furthermore, in recent years, glass fiber chopped strands have been blended with carbon fiber chopped strands, and conversely, carbon fiber chopped strands have been blended with glass fiber chopped strands. It has been proposed to improve the conventional G-SMC and C-SMC. A composition in which different types of fibers are mixed and hybridized is generally called a hybrid SMC.

[Problems to be Solved by the Invention] However, although the conventional hybrid SMC can increase the rigidity, the obtained hybrid SMC has a very large number of bundles of highly elastic fiber strands used.
However, there was a problem that stress was concentrated around the highly elastic strands, and therefore sufficient improvement could not be obtained in terms of strength and fatigue durability.

It is an object of the present invention to provide a fiber reinforced resin composition having excellent rigidity, strength and fatigue durability as compared with conventional hybrid SMC.

[Means for Solving the Problems] The fiber-reinforced resin composition of the present invention is a fiber-reinforced resin composition comprising a resin component and chopped strands dispersed in the resin component, wherein the chopped strands bundle glass fibers. Having a higher elastic modulus than the glass fiber chopped strands cut by the glass fiber, the high-elasticity chopped strands obtained by bundling and cutting 3000 or less high-elasticity inorganic fibers having a fiber bundle number considerably smaller than conventional, The amount of chopped strands is 30 to 50% by volume when the entire fiber-reinforced resin composition is 100% by volume, and the mixing ratio of the highly elastic chopped strands is 100% by volume of the entire chopped strands. It is characterized in that it is 2 to 30% by volume. As a result, both strands are evenly dispersed, and the structure is such that stress concentration around the high-elasticity fiber strand that occurs in the conventional hybrid SMC is less likely to occur.

Here, the chopped strand is obtained by cutting the strand. In the present invention, two types of strands are cut at the same time. That is, a glass fiber chopped strand obtained by cutting a glass fiber strand and a highly elastic chopped strand obtained by cutting an inorganic fiber strand having a fiber bundle number of 3000 or less as a high elastic inorganic fiber are used.

By setting the number of fiber bundles of this highly elastic inorganic fiber strand to 3000 or less, the cross-sectional area of the strand becomes small, and when the filling amount of the strand to be filled is constant, the number of strands per unit volume is more than that of the conventional product. Also increases. Therefore, the strands are finely dispersed in the resin composition, and the characteristics such as rigidity and strength of the resin composition are improved.

As described above, there is a certain relationship between the number of fiber bundles of the strand and the cross-sectional area, and the carbon fibers used in this example have the relationship as shown in Table 1.

Furthermore, in more detail, it is considered that the following structure is developed by finely dispersing the strands in the resin composition.

(I) The proportion of highly elastic inorganic fiber strands arranged near the surface of the molded plate is high. (See FIGS. 10 and 11 in the seventh embodiment) This is because the number of strands is increased, so that the high elastic inorganic fibers are more likely to be arranged in the vicinity of the surface of the molding plate.

SMC molded plate is generally often used for members subjected to bending load, when a high elastic modulus strand is arranged in the vicinity of the surface of the molded plate as in the present invention, this strand shares the stress, and as a result, The rigidity and strength of the molded plate are improved. In particular, when the proportion of the highly elastic inorganic fiber strands in the blended amount of the chopped strands is 30% by volume or more, the effect of the present invention is reduced, but even in the conventional product, the proportion of the highly elastic inorganic fiber strands is 30% by volume. %, It is considered that the amount of the highly elastic inorganic fiber strands arranged in the vicinity of the surface of the molded plate increased, and the difference from the present invention disappeared. For example, when the number of bundles of the highly elastic inorganic fiber strands is 200 or less (the cross-sectional area of the carbon fiber strands of this example is 0.01 mm ² or less), it is compared with the conventional product (the number of bundles is 1200 and the sectional area is 0.6 mm ² ). Then, the number of strands becomes 60 times, and the number of elastic inorganic fiber strands arranged on the surface of the molding plate also increases.However, if the number of strands becomes too large, the aggregate state of the strands before impregnating the resin will increase the bulk. The density becomes extremely high, and thus impregnation of the resin is likely to occur, which becomes a defect and causes a decrease in strength of the molded plate.

(II) Highly elastic inorganic fiber strands often cross each other (bridging).

That is, in the present invention, since the number of strands increases, the ratio of highly elastic inorganic fiber strands that overlap each other increases.

Since the conventional product has a small number of highly elastic inorganic fiber strands, the strands have a high probability of being dispersed without crossing each other. When the strands are dispersed singly as one strand, stress concentrates around the strands, and as a result, cracks easily occur around the strands and the strength decreases. Therefore, in order to avoid stress concentration, it is effective to cross the strands to disperse the stress. In the present invention, compared to the conventional product,
For example, when the cross-sectional area of a strand is 0.05 mm ² , the number of strands is 12 times, and when the cross-sectional area is 0.01 mm ² , it is 60 times, and the number of crossed strands is dramatically increased, resulting in uniform stress. Strength is improved.

However, if the cross-sectional area is less than 0.01 mm ² , impregnation is likely to occur, and even if the number of crosses increases, there is a impregnation defect and the strength decreases.

(III) Although the cross-sectional area of the highly elastic inorganic fiber strand becomes smaller, the number of strands increases, so that the total surface area of the side faces of the strand increases.

For example, assuming that a strand having a cross-sectional area of 0.6 mm ² which is a conventional product is a cylinder, the diameter is 0.874 mm, and the length of the strand is 1, and the side surface area thereof is 2.745 lmm ² . On the other hand, in the strand having a cross-sectional area of 0.5 mm ² in the present invention,
The diameter is 0.2523 mm, and the side surface area per strand is 0.792 lmm ² . However, since the number is 12 times, the total area is 3.510 lmm ² , which is 3.5 times that of the conventional product. Therefore, it is considered that the stress transmission efficiency to the strands is significantly enhanced, and the strength and rigidity of the present invention are enhanced.

(IV) The destruction mechanism changes. (Refer to the photograph of FIGS. 12 and 13 in the seventh embodiment) In the SMC hybridized with the highly elastic inorganic fiber strand and the glass fiber strand, a load is applied to the forming plate because the elastic modulus of the highly elastic inorganic fiber and the glass fiber is greatly different. Since a large shearing force is generated at the boundary between the highly elastic inorganic fiber strand and the glass fiber strand, a crack is generated there, and the crack propagates along the boundary. In the conventional product, the large cross-sectional area of the strand caused the crack to grow rapidly and linearly, leading to the fracture of the formed plate.

In the present invention, since the cross-sectional area of the strand is small, even if a crack is generated, its size is small, and because the strand is finely dispersed, the crack does not progress linearly, but a large number. While branching into, gradually progress. Therefore, the strength of the product of the present invention is high and the fatigue property is significantly improved.

Further, the mixing ratio of all the chopped strands described above,
When the volume of the entire resin composition is 100% by volume, it is preferably in the range of 30 to 50% by volume. If the blending ratio is less than 30% by volume, the absolute value of the strength is low, which makes it unsuitable as an industrial material. On the other hand, if it exceeds 50% by volume, the impregnation of the resin will increase and the strength will decrease.

The chopped strand has a length of 1/4 to 2
Those in the inch range are preferred. (More preferably 1/2
Within the range of ~ 3/2 inch. ) If it is less than 1/2 inch, the absolute value of the strength becomes low and it becomes unsuitable as an industrial material. On the other hand, if it exceeds 3/2 inches, the linearity of the strand is lost, and impregnation of the resin occurs, resulting in a decrease in strength.
Further, it is preferable that they are randomly dispersed in a resin composition in a plane. Further, the mixing ratio of the highly elastic chopped strands in the total amount of the chopped strands is preferably within the range of 2 to 30% by volume. If the blending ratio is less than 2% by volume, the absolute value of the amount of the highly elastic inorganic fiber becomes very small, and the hybrid effect decreases. Moreover, even if it exceeds 30% by volume, the hybrid effect will decrease.

The cross-sectional area of this highly elastic inorganic fiber strand is 0.01-0.15
It is recommended to set it within the range of mm ² . If the cross-sectional area is less than 0.01 mm ² , the strands are finely dispersed and the bulk density becomes too high, resulting in poor impregnation of the resin, which becomes a defect, leading to a decrease in rigidity and strength. Further, even if it exceeds 0.15 mm ² , the rigidity and strength will be reduced. As the resin component impregnated in the glass fiber chopped strand and the highly elastic chopped strand, it is preferable to use a thermosetting resin, for example, an unsaturated polyester resin, an epoxy resin, or a vinyl ester resin.

[Example] As a method for producing the resin composition of the present invention, a conventional general method can be used. For example, taking the production of a hybrid SMC as an example, there are the following methods.

As shown in FIG. 1, the glass fiber strand 2 is paid out from the roving 1 on which the glass fiber strand 2 in which the glass fibers are bundled is wound. At the same time, roving 1
Also, the carbon fiber strands 24 that bundle the carbon fibers from the rovings 4 that are juxtaposed at a distance in the axial direction are drawn.

The glass fiber strand 2 is conveyed to the chopper 5 via the guide rollers 3 and 4. On the other hand, the carbon fiber strands 24 are guided to the chopper 54 adjacent to the chopper 5 by the guide rollers 34 and 44 provided coaxially (not shown) with the guide rollers 3 and 4, respectively. Each strand
2a and 24a are cut into lengths of about 1 inch by the choppers 5 and 54, respectively, and the fibers fall while being bundled. The dropped glass fiber chopped strands 2a and carbon fiber chopped strands 24a are deposited on the plastic sheet 7a supplied from the first sheet roll 7. The resin component supplied from the first resin retainer 8 is applied to the plastic sheet 7a. (The resin component is composed of unsaturated polyester, organic peroxide for curing, mold release agent, and thickener.) Since the plastic sheet 7a is moving rightward in the figure, chopped The strands 2a and 24a are distributed in a state of being evenly mixed on the plastic sheet 7a without being deposited at one place on the plastic sheet 7a. However,
Since the chopped strands 2a and 24a face an arbitrary direction in the dropping process, they are randomly dispersed on the plastic sheet 7a in a plane.

On the other hand, the plastic sheet 9a supplied from the second sheet roll 9 covers the chopped strands 2a and 24a from above.
This plastic sheet 9a is also coated with the same resin component as that supplied from the second resin retainer 10.

Therefore, the chopped strands 2a and 24a are impregnated with resin from both sides thereof. Thus, the chopped strands 2a and 24a sandwiched between the upper and lower plastic sheets 7a and 9a are wound by the winding roll 11 while being impregnated with the resin. As a result, a hybrid SMC in which glass fiber strands and carbon fiber strands are randomly dispersed is obtained. The single-layer hybrid SMC may be cut into a predetermined size, the plastic sheets 7a and 9a may be peeled off, and the single-layer hybrid SMC may be laminated to form a multi-layer hybrid SMC. Hybrid SMC molding is done with plastic sheets 7a, 9
It is carried out by heating and pressurizing the resin in a heating mold in a state where a is peeled off to cure the resin. In the conventional hybrid SMC, the number of carbon fiber strands bundled with the carbon fibers supplied from the roving 4 was generally 12000 or more, but in the present invention, 3000 or less carbon fiber strands are used. Further, in the case of using the conventional 12000 or more strands without using 3000 or less carbon fiber strands, conventionally in the chopper 54, only to cut the strand to a predetermined length, the chopper 54 It is possible to improve the structure by adding a mechanism of cutting the strand to a predetermined length and at the same time dividing the strand in the axial direction, and dividing one strand into a large number and processing it into 3000 or less strands.

Hereinafter, examples of the fiber-reinforced resin composition of the present invention will be described.

The relationship between the number of fiber bundles of carbon fiber strands and the cross-sectional area in this example is shown in Table 1 above.

(First Example) A hybrid SMC in this example is a glass fiber chopped strand in which about 200 glass fibers are bundled,
A carbon fiber chopped strand in which 3000 or less carbon fibers are bundled is mixed, and these are dispersed in an unsaturated polyester resin.

In this embodiment, the number of carbon fiber bundles is 500, 1000, 300
Instead of 0, a total of 3 hybrid SMCs were produced as described above for FIG. The total volume of the carbon fiber strands 24 and the glass fiber strands 2 is 40% by volume of the entire hybrid SMC molded product.
And the ratio of carbon fiber strands to glass fiber strands was 1: 9.

Further, in the present embodiment, the example in which the glass fiber strand 2 and the carbon fiber strand 24 are simultaneously drawn out from the different rovings 1 and 4 and cut by the different choppers 5 and 54 is shown, but both strands 2 and 24 are common. A configuration using a chopper may be used.

Next, two types of hybrid SMCs were prepared by the same manufacturing method as in the above-mentioned examples using conventional chopped strands having 6000 and 12000 carbon fiber bundles for comparison with the examples of the fiber-reinforced resin composition of the present invention. It was manufactured and designated as Comparative Example 1 and Comparative Example 2. For experiment, each of these single-layer hybrid SMCs and the hybrid SMCs produced in the above examples were laminated in 10 layers, and pressure-molded at a temperature of 150 ° C. and a pressure of 150 kg / cm ² for 3 minutes, and a plate-shaped molded product having a thickness of 3 mm Got Further, a conventional G-SMC in which glass fiber chopped strands and a resin component were integrated was separately manufactured and molded for experiment, and prepared as Comparative Example 3. Then, the blending and mechanical properties of the fiber and resin in the molded product of each hybrid SMC were measured. Second measurement result
Shown in the table. The rigidity and strength were determined by performing a 3-point bending test under the conditions of a test piece having a width of 25 mm and a thickness of 3 mm and a span of 80 mm. The acoustic emission was measured during the 3-point bending test. Fatigue test width 20mm, thickness
Minimum stress at a frequency of 10 Hz using a 3 mm, 220 mm long test piece
The test was carried out under tensile conditions of 1 kg / mm ² and maximum stress of 10 kg / mm ² , and the number of times the load was repeated until the test piece broke was determined.

As shown in Table 2, when the whole glass fiber of the example is set to 100% by volume, 10% by volume (1: 9) of which 500 bundles are collected, and 1000
The hybrid SMC molded product replaced with the carbon fiber strands with the main focus and the 3000 fiber bundles is more glass than the hybrid SMC molded product with the carbon fiber strands with the 6000 fiber bundles and the 12000 fiber bundles (Comparative Examples 1 and 2). It can be seen that the mechanical properties are remarkably improved over the G-SMC molded product made of fibers (Comparative Example 3).

The bending rigidity and bending strength shown in Table 2 are shown in FIGS. 2 and 3. In addition, in the figure, the graph is made based on the cross-sectional area of the carbon fiber strand. In addition, the data of the cross-sectional area of the carbon fiber strand is 0.01mm ² (200 when the number of fibers is used) is added.

As it is clear from FIGS. 2 and 3, in the range cross-sectional area of 0.01～0.15Mm ² of carbon fiber strand, bending rigidity and bending strength as compared with Comparative Example 2 is a cross-sectional area was 0.6 mm ² It turns out that is dramatically improved.

(Second Example) A glass fiber strand, a carbon fiber strand and an unsaturated polyester resin are used, and the ratio of the carbon fiber strand to the glass fiber strand is (1: 9), (2: 8),
Instead of (3: 7), three types of single-layer hybrid SMCs were manufactured by the same method as in the first embodiment described above. The total volume of the carbon fiber strands and the glass fiber strands was set to 40% by volume when the total volume of the hybrid SMC was 100% by volume. In this example, carbon fiber strands having a number of 1000 bundles were used as the carbon fibers.

(Experiment 2) In the same manner as in the above-mentioned first embodiment, the number of focused beams is set as a comparative example.
Hybrid SMC using 12000 carbon fiber strands
A conventional G-SMC consisting of and only glass fiber was manufactured.

Single-layer hybrid SM as each of the above-mentioned examples and comparative examples
10 layers of C and G-SMC are laminated, and the temperature is 150 ℃ and the pressure is 150kg / cm ² .
Pressure molding was performed for 1 minute to obtain a plate-shaped molded product having a thickness of 3 mm. The flexural rigidity, flexural strength and fatigue level of these molded products were measured, and the measurement results are shown in Table 3.

When the volume% of the entire glass fiber is 100% by volume, 1
The fiber-reinforced resin composition of this example, in which 0 volume% (1: 9), 20 volume% (2: 8), and 30 volume% (3: 7) were replaced by 1000-focused carbon fibers, 10% by volume (1: 9), 2
Compared to the hybrid SMC molded product (Comparative Example 1) in which 02000% by volume (2: 8) and 30% by volume (3: 7) were replaced by carbon fiber strands with 12000 bundles (Comparative Example 1), G-SM using all glass fibers was used.
It was found that the mechanical properties were generally improved as compared with the C molded product (Comparative Example 2), and in particular, the bending strength was increased by 20% or more.

The bending rigidity and bending strength shown in Table 3 are shown in FIGS. 4 and 5. The horizontal axis of the figure is the ratio of carbon fiber volume to glass fiber deposition. Data with ratios of 0.2: 9.8 and 4: 6 are also added.

As is clear from FIGS. 4 and 5, when the proportion of carbon fibers in the total fiber amount is 2 to 30% by volume,
The present invention is more hybrid than the comparative example (G-SMC and C-SMC
The difference between the arithmetic mean of
10-20% by volume and 10-20 for bending strength
In the case of volume%, an extreme difference appears in the hybrid effect, and the flexural modulus is significantly improved as compared with the comparative example.
However, it can be seen that when the ratio of the fibers is more than the above range, the carbon bridging effect is the same as that of the comparative example, and the hybrid effect of the present invention takes the maximum value within the above range.

(Third Example) The hybrid SM was changed in the same manner as in the first example by changing the volume fraction occupied by all the fibers under the condition that the volume ratio of the glass fiber strand and the carbon fiber strand was kept constant at 9: 1.
C was produced. Figure 6 shows the bending strength of the hybrid SMC.

As is clear from FIG. 6, the flexural strength of the present invention was superior to that of the comparative example, and showed the maximum value when the volume fraction was 40.

(Fourth Example) Under the condition that the volume ratio of the glass fiber strands and the volume of the carbon fiber strands was set to 9: 1, and the ratio of the volume of the two to the total volume of the material was kept constant at 40%. 1/2 the length of glass fiber strand and carbon fiber strand
A hybrid SMC was manufactured in the same manner as in the first embodiment, changing from inch to 3/2 inch. This hybrid SMC
FIG. 7 shows the blistering strength of the hair.

As is clear from FIG. 7, those of the present invention showed a bending strength superior to that of the comparative example, and showed the maximum value when the length was 1 inch.

(Fifth Example) A hybrid SMC in which the ratio of the glass fiber chopped strands and the carbon fiber chopped strands was changed was produced in the same manner as in the first example except that an epoxy resin was used as the resin. The bending strength of this hybrid SMC is shown in FIG.

As is clear from FIG. 8, in the range of the carbon fiber ratio of 2 to 30% by volume, the bending strength of the carbon fiber of the present invention is remarkably improved as compared with the comparative example.

(Sixth Example) A hybrid SMC having different cross-sectional areas of carbon fiber strands was produced in the same manner as in the first example except that an epoxy resin was used as the resin. The bending strength of this hybrid SMC is shown in FIG.

As is clear from Figure 9, the bending strength than the comparative example in the range cross-sectional area of the carbon fiber strand is 0.01～0.15Mm ² has dramatically improved, a maximum value in the case of 0.05 mm ² I know that

(Seventh Example) A hybrid SMC molded body produced in the same manner as in the first example except that the mixing ratio of the glass fiber chopped strands and the carbon fiber chopped strands was 9: 1 and the total fiber amount was 40% by volume. 10 to 13 are photographs (magnification 25 times) showing the shape of the fibers in the cross section of the above, instead of the drawings. In addition,
The number of carbon fiber chopped strands is 1000 in FIGS. 10 and 12, and 12000 in FIGS. 11 and 13. First
Comparing FIG. 0 and FIG. 11, FIG. 12 and FIG. 13, in the present invention, the carbon fiber chopped strands are finely dispersed, and the cracks are also finely dispersed, so that the cracks develop. You can see that not.

[Effects of the Invention] The hybrid SMC of the present invention in which the glass fiber strands obtained in the present invention and the thin high-elasticity inorganic fiber strands are finely dispersed, the conventional glass fiber strands and the thick high-elasticity inorganic fiber strands are unevenly distributed. Compared to the hybrid SMC that is dispersed, it has higher rigidity and can have dramatically improved strength and durability. Especially when compared to G-SMC consisting exclusively of glass fiber strands, the hybrid SMC of the present invention is far superior in its mechanical properties by substituting slightly higher modulus inorganic fiber strands. Generally, the highly elastic inorganic fiber strand is expensive, but the hybrid of the present invention
According to the SMC, even when the amount of the highly elastic inorganic fiber is small, it is possible to expect the characteristics that are higher than those of the conventional hybrid SMC.

Further, the method for producing the hybrid SMC of the present invention is the same as the conventional method, and therefore, the hybrid SMC having higher quality than the conventional method can be produced at low cost.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a manufacturing apparatus in one example of the fiber-reinforced resin composition of the present invention, FIG. 2 is a graph showing a bending elastic modulus of the resin composition in the example, FIG. 3, and FIG. FIG. 9 is a graph showing the bending strength of the resin composition in each example, FIG. 4 is a graph showing the bending rigidity of the resin composition in the examples, and FIGS. 10 and 12 are graphs showing the examples of the present invention. A photograph showing the shape of the fiber in the cross section of the SMC hybrid molded plate made of the resin composition in place of the drawing (magnification:
25 times), FIGS. 11 and 13 are made of the resin composition of the comparative example.
It is a photograph (magnification 25 times) showing the shape of the fiber in the cross section of the SMC hybrid molded plate in place of the drawing. 2a …… Glass fiber chop strands 24a …… Carbon fiber chop strands

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Kageyama 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Inventor Masatsugu Sakamoto 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. ( 72) Inventor Norio Sato 41, Nagachote, Nagakute-cho, Aichi-gun, Aichi Prefecture 1 of Toyota Central Research Institute Co., Ltd. Company Toyota Central Research Institute (72) Inventor Norio Kurauchi 1st 41st Yokomichi Nagakute-cho, Aichi-gun, Aichi Prefecture Toyota Central Research Institute

Claims (2)

[Claims] 1. A fiber-reinforced resin composition comprising a resin component and chopped strands dispersed in the resin component, wherein the chopped strand is higher than the glass fiber chopped strand obtained by focusing and cutting glass fibers and the glass fiber. Having an elastic modulus, the number of fiber bundles consists of high-elasticity chopped strands obtained by bundling and cutting high-elasticity inorganic fibers of 3000 or less, and the compounding amount of the chopped strands is
30 to 50 when the total volume of the fiber-reinforced resin composition is 100%
%, And the compounding ratio of the highly elastic chopped strands is 10% based on the total amount of the chopped strands.
A fiber-reinforced resin composition, which is 2 to 30% by volume when 0% by volume. 2. The fiber-reinforced resin composition according to claim 1, wherein the resin component is a thermosetting resin.