JP2018134789A - Fiber reinforced resin material and fiber reinforced resin molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber-reinforced resin molded article that can exhibit good mechanical properties in which interfacial failure between carbon fibers and a matrix resin hardly occurs even when carbon fibers having high tensile elastic modulus are used, and a fiber-reinforced resin material excellent in moldability capable of obtaining such a fiber-reinforced resin molded article.SOLUTION: The fiber reinforced resin material includes: a plurality of carbon fibers; and a resin material containing either or both of a thermosetting resin and a thermoplastic resin. A product Lf×Er/Ef of a ratio Er/Ef of a tensile modulus of elasticity Er (GPa) of the resin material (however, in the case of including the thermosetting resin, the thermosetting resin is cured.) with respect to a tensile modulus of elasticity Ef (GPa) of the carbon fiber and a fiber length Lf (mm) of the carbon fiber is in a range of 0.2 to 0.8.SELECTED DRAWING: None

Description

  The present invention relates to a fiber reinforced resin material and a fiber reinforced resin molded body obtained by molding the fiber reinforced resin material.

  As an intermediate material used in the manufacture of a fiber reinforced resin molded article having a complicated shape having parts with different thicknesses, ribs, bosses, etc., the moldability is good because the reinforcing fibers are composed of chopped fibers. There are sheet molding compounds (hereinafter abbreviated as SMC), stampable seats, and the like. SMC impregnates a sheet-like carbon fiber bundle group formed by depositing short carbon fiber bundles (chopped carbon fiber bundles) obtained by cutting long carbon fiber bundles into a predetermined length with a thermosetting resin. Fiber reinforced resin material. The stampable sheet is a fiber reinforced resin material in which a chopped fiber bundle is impregnated with a thermoplastic resin.

As a fiber reinforced resin molding which shape | molded the fiber reinforced resin material, the following are mentioned, for example.
(1) A chopped fiber bundle in which the number of filaments is in the range of 10,000 to 700,000 in which the reinforcing fibers having a fiber length in the range of 5 to 100 mm are substantially aligned in one direction is a matrix resin. And a ratio (Wm / tm) of an average width Wm and an average thickness tm of the chopped fiber bundle in the molding material is in a range of 70 to 1,000, and chopped fibers A fiber reinforced resin molded article obtained by molding a molding material having an average bundle width Wm of 2 to 50 mm and an average thickness tm of 0.02 to 0.1 mm (Patent Document 1).
(2) A fiber reinforced resin molded article made of a reinforcing fiber dispersed in a single fiber and a thermoplastic resin, and a maximum value Dmax and a minimum value Dmin of relative frequencies in increments of 10 ° in the in-plane angular frequency distribution of the reinforcing fibers. Is a relationship of Dmax−Dmin ≦ 0.08, the maximum fiber length (lmax) in the length distribution of the reinforcing fibers is 5 lc or less with respect to the critical fiber length (lc), and the amount of reinforcing fibers occupying the fiber lengths lc to 5lc A fiber-reinforced resin molded article having a volume ratio (Va) of 40 to 90%, an average value of out-of-plane angles of reinforcing fibers of 6 ° or less, and a thickness of 1.5 to 4 mm in a plane portion (Patent Document) 2).

JP 2009-062474 A JP 2014-0197780 A

As one of the methods for obtaining a fiber reinforced resin molded article having excellent mechanical properties, it is conceivable to use a carbon fiber having high tensile elasticity such as pitch-based carbon fiber and having high rigidity.
However, in the molding material (1) and the fiber reinforced resin molding (2), carbon fibers having a general-purpose grade stiffness (tensile elastic modulus is 200 to 300 GPa) are used, and the tensile elastic modulus is 300 GPa. High-rigidity carbon fibers exceeding the above have not been studied.

  Further, in order to exhibit good mechanical properties in a fiber reinforced resin molded article using a short carbon fiber bundle, it is necessary that the carbon fiber and the matrix resin are firmly bonded. However, in a fiber reinforced resin molded article using high-rigidity carbon fibers, the difference between the tensile elastic modulus of the carbon fibers and the tensile elastic modulus of the matrix resin increases. Therefore, when a load is applied to the fiber reinforced resin molded product, the stress concentration generated at the interface between the carbon fiber and the matrix resin tends to increase. In addition, local strain tends to occur in the matrix resin after the interface breakage. Therefore, when high-rigidity carbon fibers are used in the molding material (1) and the fiber-reinforced resin molding (2), interface fracture between the carbon fibers and the matrix resin is likely to occur, and sufficient mechanical properties are exhibited. It becomes difficult.

  The present invention provides a fiber reinforced resin molded article that is less likely to cause interface fracture between carbon fibers and a matrix resin even when carbon fibers having a high tensile elastic modulus are used, and can exhibit good mechanical properties. Provided is a fiber reinforced resin material which can obtain a fiber reinforced resin molded article and is excellent in moldability.

The present invention has the following aspects.
<1> a plurality of carbon fibers and a resin material containing one or both of a thermosetting resin and a thermoplastic resin, and the resin material for the tensile elastic modulus Ef (GPa) of the carbon fiber (however, When the thermosetting resin is included, the thermosetting resin is cured.) The product Lf × Er of the ratio Er / Ef of the tensile elastic modulus Er (GPa) and the fiber length Lf (mm) of the carbon fiber. / Ef is a fiber reinforced resin material in the range of 0.2 to 0.8.
<2> The fiber reinforced resin material according to <1>, wherein a volume content of the carbon fiber is 20% by volume or more and less than 65% by volume out of 100% by volume of the fiber reinforced resin material.
<3> A fiber-reinforced resin molded article obtained by molding the fiber-reinforced resin material according to <1> or <2>.

According to the fiber reinforced resin material of the present invention, even when carbon fibers having a high tensile elastic modulus are used, the fiber reinforced resin is capable of exhibiting good mechanical properties without causing interface fracture between the carbon fibers and the matrix resin. A molded body can be obtained. Moreover, the fiber reinforced resin material of this invention is excellent in a moldability.
The fiber reinforced resin molded article of the present invention is less likely to cause interfacial breakage between the carbon fiber and the matrix resin even when carbon fiber having a high tensile modulus is used, and can exhibit good mechanical properties.

It is a perspective view of the simulation model (fiber reinforced resin molding) used in the example. It is II-II sectional drawing of FIG. It is III-III sectional drawing of FIG.

The following definitions of terms apply throughout this specification and the claims.
“Tensile elastic modulus of carbon fiber” is a value measured in accordance with JIS R 7606: 2000 “Testing method for tensile properties of carbon fiber-single fiber” (corresponding international standard ISO 11566: 1996).
The “tensile elastic modulus of the resin material” was measured in accordance with JIS K 7161-1: 2014 “Plastics—Method of obtaining tensile properties—Part 1: General rules” (corresponding international standard ISO 527-1: 2012). Value.
As a method for measuring “interfacial shear strength between carbon fiber and matrix resin”, a microdroplet method and a fragmentation method are known. In this specification, the microdroplet method is employed.
In the “microdroplet method”, resin particles (droplets) are attached to single fibers, and after fixing the droplets, the interfacial adhesion between the single fibers and the resin is determined by performing a pull-out test of the single fibers from the droplets. It is a method to evaluate. In the microdroplet method, the interfacial shear strength is calculated from the following equation.
τ = F / (πDL)
Where τ is the interfacial shear strength, F is the maximum pulling load, L is the length of the single fiber embedded in the droplet, and D is the fiber diameter of the single fiber.
“˜” indicating a numerical range means that numerical values described before and after the numerical value range are included as a lower limit value and an upper limit value.
The dimensional ratios in FIGS. 1 to 3 are different from actual ones for convenience of explanation.

<Fiber-reinforced resin material>
The fiber-reinforced resin material of the present invention includes a plurality of carbon fibers and a resin material containing one or both of a thermosetting resin and a thermoplastic resin.
Since the fiber reinforced resin material has high fluidity by heating, it is used as an SMC for manufacturing fiber reinforced resin molded products having various shapes.

  In the fiber reinforced resin material of the present invention, the tensile elastic modulus Er of a resin material (however, when a thermosetting resin is included, the thermosetting resin is cured) with respect to the tensile elastic modulus Ef (GPa) of the carbon fiber. The product Lf × Er / Ef of the ratio Er / Ef of (GPa) and the fiber length Lf (mm) of the carbon fiber is in the range of 0.2 to 0.8, and is in the range of 0.2 to 0.6. It is preferable that it exists in. When Lf × Er / Ef is not less than the lower limit of the above range, a fiber-reinforced resin molded article having excellent mechanical properties can be obtained. When Lf × Er / Ef is equal to or less than the upper limit of the above range, the fiber length Lf of the carbon fiber becomes sufficiently short, and the moldability of the fiber reinforced resin material is excellent.

Lf × Er / Ef is an equation indicating the balance between the mechanical properties of the fiber-reinforced resin molded product and the moldability of the fiber-reinforced resin material.
As the tensile elastic modulus Ef of the carbon fiber is higher, higher rigidity is expected in the fiber-reinforced resin molded body. However, as the difference from the tensile modulus Er of the resin material (corresponding to the matrix resin) increases, that is, as Er / Ef decreases, the stress generated at the interface between the carbon fiber and the matrix resin increases, and the carbon fiber and the matrix resin The mechanical properties of the fiber-reinforced resin molded product are likely to be reduced by promoting interfacial fracture. Further, from the viewpoint of mechanical properties of the fiber reinforced resin molded product, it is more effective that the fiber length Lf of the carbon fiber is longer, but from the viewpoint of moldability of the fiber reinforced resin material, the fiber length Lf of the carbon fiber is The shorter one is more effective. Therefore, in order to balance the mechanical properties of the fiber-reinforced resin molded body and the moldability of the fiber-reinforced resin material, it is necessary to adjust the relationship between Lf, Er, and Ef. Specifically, Lf × Er / Ef is set to It may be within the above range.

(Carbon fiber)
When Lf × Er / Ef is within the above range, the fiber length Lf of the carbon fiber is sufficiently short. Therefore, the carbon fiber in the present invention is usually a short carbon fiber obtained by cutting a long carbon fiber.
The short carbon fiber is preferably a short carbon fiber bundle obtained by cutting a long carbon fiber bundle, so-called chopped carbon fiber bundle, from the viewpoint of mechanical properties of the fiber reinforced resin molded product.
Examples of the long carbon fiber bundle include a tow or the like in which a plurality of carbon fibers are aligned in a uniaxial direction.

Examples of the carbon fiber include PAN-based carbon fiber and pitch-based carbon fiber. The raw material and manufacturing method of carbon fiber are not particularly limited. The carbon fiber may be subjected to a surface treatment in order to improve adhesiveness with the matrix resin in the fiber reinforced resin molded body.
Carbon fiber may be used individually by 1 type, and may use 2 or more types together.

  The tensile elastic modulus Ef of the carbon fiber is preferably more than 300 GPa and 800 GPa or less, and more preferably 400 to 700 GPa. If the tensile elastic modulus Ef of the carbon fiber is not more than the upper limit of the above range, a fiber reinforced resin molded article having further excellent mechanical properties can be obtained. When the tensile elastic modulus Ef of the carbon fiber is equal to or less than the upper limit of the above range, interfacial breakage between the carbon fiber and the matrix resin is suppressed, and stable physical properties are obtained.

  The fiber length Lf of the carbon fiber is preferably 20 to 100 mm, and more preferably 50 to 75 mm. If the fiber length Lf of the carbon fiber is equal to or less than the upper limit of the above range, a fiber reinforced resin molded article with further excellent mechanical properties can be obtained. If the fiber length Lf of the carbon fiber is not more than the upper limit of the above range, the moldability of the fiber reinforced resin material is further improved. When a plurality of carbon fibers having different fiber lengths Lf are included, the fiber length Lf of the carbon fibers is an average value.

  The volume content Vf of the carbon fiber is preferably 20% by volume or more and less than 65% by volume, more preferably 30 to 50% by volume, out of 100% by volume of the fiber reinforced resin material. If the volume content Vf of the carbon fiber is equal to or higher than the lower limit of the above range, a fiber-reinforced resin molded article with further excellent mechanical properties can be obtained. If the volume content Vf of the carbon fiber is less than or equal to the upper limit of the above range, the fiber reinforced resin material is more excellent in moldability and a fiber reinforced resin material suitable for an intermediate material of a fiber reinforced resin molded body having a complicated shape is obtained. It is done.

(Resin material)
The resin material includes a resin and, if necessary, an additive.
Examples of the resin include one or both of a thermosetting resin and a thermoplastic resin. As the resin, a thermosetting resin is preferable from the viewpoint of mechanical properties of the fiber-reinforced resin molded body.

Examples of the thermosetting resin include an epoxy resin, an unsaturated polyester resin, a vinyl ester resin, a phenol resin, and a urethane resin. A thermosetting resin may be used individually by 1 type, and may use 2 or more types together.
The thermosetting resin may be partially or completely uncured when the fiber-reinforced resin material is molded, or may be completely cured. The thermosetting resin is in a cured state in the fiber-reinforced resin molded body.

  When the tensile elastic modulus Er of the cured product of the thermosetting resin is extremely smaller than the tensile elastic modulus Ef of the carbon fiber, when a load is applied to the fiber reinforced resin molded product, the interface between the carbon fiber and the matrix resin is applied. The resulting stress concentration increases. Therefore, as a thermosetting resin, a thing with high adhesiveness with carbon fiber in the state of hardened | cured material is preferable. When the carbon fiber is a pitch-based carbon fiber having a relatively high tensile elastic modulus Ef, the thermosetting resin is preferably a phenol resin having a relatively high tensile elastic modulus Er in a cured product state. When the carbon fiber is a PAN-based carbon fiber having a relatively low tensile elastic modulus Ef, the thermosetting resin is preferably an epoxy resin or a vinyl ester resin having a relatively low tensile elastic modulus Er in a cured product state.

  Examples of thermoplastic resins include polyamide (nylon 6, nylon 66, nylon 12, nylon MXD6, etc.), polyolefin (low density polyethylene, high density polyethylene, polypropylene, etc.), modified polyolefin (modified polypropylene, etc.), polyester (polyethylene terephthalate, poly Butylene terephthalate, etc.), polycarbonate, polyamideimide, polyphenylene oxide, polysulfone, polyethersulfone, polyetheretherketone, polyetherimide, polystyrene, acrylonitrile-butadiene-styrene copolymer, polyphenylene sulfide, liquid crystal polyester, acrylonitrile-styrene copolymer Examples include coalescence. Examples of the modified polyolefin resin include a resin obtained by modifying a polyolefin resin with an acid such as maleic acid.

  Additives include curing agents, internal mold release agents, thickeners, stabilizers, defoamers, flame retardants, weather resistance improvers, antioxidants, UV absorbers, plasticizers, lubricants, colorants, compatibilizers Examples thereof include an agent, a filler, and a conductive filler.

(Method for producing fiber-reinforced resin material)
The fiber reinforced resin material of the present invention can be produced, for example, as follows.
A short carbon fiber bundle (chopped carbon fiber bundle) obtained by cutting a long carbon fiber bundle into a predetermined length by a cutting machine is deposited in a sheet shape to form a sheet-like carbon fiber bundle group. A sheet-like carbon fiber bundle group is impregnated with a liquid resin material to obtain a fiber-reinforced resin material.

(Mechanism of action)
In the fiber reinforced resin material of the present invention described above, the resin material for the tensile elastic modulus Ef (GPa) of the carbon fiber (however, when a thermosetting resin is included, the thermosetting resin is cured). Since the product Lf × Er / Ef of the ratio Er / Ef of the tensile elastic modulus Er (GPa) and the fiber length Lf (mm) of the carbon fiber is equal to or greater than the lower limit of the above range, the difference between Er and Ef is Small and Lf is not too short. Therefore, even when carbon fibers having a high tensile elastic modulus are used, it is possible to obtain a fiber reinforced resin molded article that is less likely to cause interface fracture between the carbon fibers and the matrix resin and that can exhibit good mechanical properties. Moreover, since Lf × Er / Ef is not more than the upper limit of the above range, Lf does not become too long, and the moldability is excellent.

  In such a fiber reinforced resin material of the present invention, a carbon fiber having a high tensile elastic modulus can be used, and therefore, a fiber reinforced resin having excellent mechanical properties as compared with the case of using a general-purpose grade carbon fiber. A molded body can be obtained. Further, the volume content of carbon fibers in the fiber reinforced resin material can be reduced, and a weight-reduced fiber reinforced resin molded product can be obtained while having mechanical properties equivalent to those of a conventional fiber reinforced resin molded product. . Moreover, by reducing the volume content of the carbon fiber, the fluidity (moldability) of the fiber reinforced resin material can be improved, and the cost of the fiber reinforced resin material and the fiber reinforced resin molded product can be reduced.

<Fiber-reinforced resin molding>
The fiber reinforced resin molded article of the present invention is obtained by molding the fiber reinforced resin material of the present invention, and includes a plurality of carbon fibers and a matrix resin derived from the resin material in the fiber reinforced resin material.
The matrix resin includes a cured product of a thermosetting resin when the resin material includes a thermosetting resin, and includes the same thermoplastic resin when the resin material includes a thermoplastic resin.

  The interfacial shear strength between the carbon fiber and the matrix resin is preferably 50 MPa or more. If the interfacial shear strength is at least the lower limit of the above range, the adhesion between the carbon fibers and the matrix resin will be good, and a fiber-reinforced resin molded product with further excellent mechanical properties can be obtained. In order to increase the interfacial shear strength, a carbon fiber that has been surface-treated may be used. The higher the interfacial shear strength, the better, and the upper limit is not particularly limited.

(Manufacturing method of fiber reinforced resin molding)
The fiber reinforced resin molded article of the present invention is, for example, heated and pressurized the fiber reinforced resin material of the present invention using a mold to cause the fiber reinforced resin material to follow the shape of the mold and the resin material is thermosetting. When resin is included, it can be manufactured by curing a thermosetting resin.

(Mechanism of action)
In the fiber reinforced resin molded body of the present invention described above, since the fiber reinforced resin material of the present invention is molded, even if carbon fibers having a high tensile elastic modulus are used, It is difficult to cause interface breakdown with the matrix resin, and can exhibit good mechanical properties.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

(Evaluation of fiber reinforced resin molding)
The evaluation of the fiber reinforced resin molded body was performed by simulation using CAE (Computer Aided Engineering) software.
As CAE software, LS-DYNA (manufactured by LSTC), which is nonlinear dynamic structure analysis software, was used.
As the simulation model, the model shown in FIGS. 1 to 3 was used. 1 is a perspective view of a simulation model, FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line III-III in FIG.
As shown in FIG. 1, the simulation model 10 is a long square bar-like fiber reinforced resin molded body having a length of 2L + 1.
As shown in FIG. 2, in the simulation model 10, two carbon fibers 14 (single fibers) having a fiber length L arranged in series in the matrix resin 12 along the longitudinal direction of the simulation model 10 are long. It is buried at an interval of 1.
As shown in FIG. 3, the cross section of the simulation model 10 is a square whose length and width are both 1, and the area ratio of the carbon fiber 14 to the square is 40% (that is, the volume content Vf of the carbon fiber 14 is 40% by volume). ) So that the fiber diameter of the carbon fiber 14 is 0.71.

Using CAE software, the first end portion of both ends of the simulation model 10 is constrained, the second end portion is subjected to a forced displacement in the longitudinal direction, and the tensile modulus of the simulation model 10 (fiber reinforced resin molded body). E was calculated. The calculation range of the tensile modulus E was set to a range of 0.05 to 0.25% strain.
The theoretical tensile elastic modulus Et of the simulation model 10 (fiber reinforced resin molded body) was calculated from the following formula, which is a general calculation formula.
Et = Ef * Vf / 100 + Er * (1-Vf / 100)
However, Ef is the tensile elastic modulus of the carbon fiber 14, Vf is the volume content of the carbon fiber 14, and Er is the tensile elastic modulus of the matrix resin 12.
The ratio E / Et of the tensile elastic modulus E of the fiber-reinforced resin molded body with respect to the theoretical tensile elastic modulus Et was calculated, and 80% or more was judged as ◯ (pass), and less than 80% was judged as x (failed). If E / Et is 80% or more, it indicates that an interfacial fracture between the carbon fiber and the matrix resin is suppressed, and a fiber-reinforced resin molded article having mechanical properties close to ideal is obtained.

  Hereinafter, the influence of the fiber length Lf of the carbon fiber on the tensile elastic modulus E of the fiber-reinforced resin molded body was confirmed using the simulation model 10.

(Example A1)
The conditions for the simulation with the CAE software were as follows.
The tensile elastic modulus Ef of the carbon fiber 14 was 640 GPa assuming a pitch-based carbon fiber (Mitsubishi Rayon Co., Ltd., DIALEAD K63712).
The tensile elastic modulus Er of the matrix resin 12 was 3 GPa assuming a cured vinyl ester resin or a cured epoxy resin used in a normal fiber reinforced resin molded product.
The interfacial shear strength between the carbon fiber 14 and the matrix resin 12 was set to 50 MPa with reference to an actual measurement value by a microdroplet method.
The fiber length L of the carbon fiber 14 was 3500. The length of the simulation model 10 is 7001. The fiber diameter of the general-purpose grade of the pitch-based carbon fiber is 10 μm, and the fiber length Lf of the carbon fiber in the actual fiber reinforced resin molded body is calculated from the ratio of the fiber diameter and the fiber length of the carbon fiber 14 in the simulation model 10 , Corresponding to 49.0 mm.

  Using CAE software, the tensile elastic modulus E of the simulation model 10 (fiber reinforced resin molded product) was calculated. Further, the theoretical tensile elastic modulus Et of the simulation model 10 (fiber reinforced resin molded body) was calculated.

(Example A2)
Except for changing the fiber length L of the carbon fiber 14 to 5000 (the length of the simulation model 10: 10001, the fiber length Lf of the carbon fiber in the actual fiber-reinforced resin molded product: equivalent to 70.1 mm), the same as in Example A1 Thus, the tensile elastic modulus E and the theoretical tensile elastic modulus Et of the simulation model 10 (fiber reinforced resin molded body) were calculated.

(Comparative Example A1)
Except for changing the fiber length L of the carbon fiber 14 to 1750 (the length of the simulation model 10: 3501, the fiber length Lf of the carbon fiber in the actual fiber-reinforced resin molded product: equivalent to 24.5 mm), the same as in Example A1 Thus, the tensile elastic modulus E and the theoretical tensile elastic modulus Et of the simulation model 10 (fiber reinforced resin molded body) were calculated.

(Comparative Example A2)
Except for changing the fiber length L of the carbon fiber 14 to 2500 (the length of the simulation model 10: 5001, the fiber length Lf of the carbon fiber in the actual fiber-reinforced resin molded product: equivalent to 35.0 mm), the same as in Example A1 Thus, the tensile elastic modulus E and the theoretical tensile elastic modulus Et of the simulation model 10 (fiber reinforced resin molded body) were calculated.

The results of Example A1, Example A2, Comparative Example A1, and Comparative Example A2 are summarized in Table 1.
It can be seen that when the ratio Er / Ef of the tensile elastic modulus Ef of the carbon fiber 14 and the tensile elastic modulus Er of the matrix resin is constant, the mechanical characteristics improve as the fiber length Lf of the carbon fiber increases. When the product of Lf and Er / Ef was 0.2 or more, the tensile elastic modulus E of the fiber-reinforced resin molded product was 80% or more of the theoretical value, and good rigidity was obtained.

  Hereinafter, the influence of the tensile elastic modulus Er of the matrix resin on the tensile elastic modulus E of the fiber-reinforced resin molded body was confirmed using the simulation model 10.

(Example B1)
The tensile elastic modulus Er of the matrix resin 12 is changed to 6 GPa, and the fiber length L of the carbon fiber 14 is 1750 (the length of the simulation model 10: 3501, the fiber length Lf of the carbon fiber in the actual fiber reinforced resin molded product: 24. Except for the change to equivalent to 5 mm, the tensile modulus E and the theoretical tensile modulus Et of the simulation model 10 (fiber reinforced resin molded body) were calculated in the same manner as in Example A1.

(Example B2)
The tensile elastic modulus Er of the matrix resin 12 is changed to 6 GPa, and the fiber length L of the carbon fiber 14 is 2500 (the length of the simulation model 10: 5001, the fiber length Lf of the carbon fiber in the actual fiber-reinforced resin molded product: 35. Except for changing to 0 mm equivalent), the tensile elastic modulus E and the theoretical tensile elastic modulus Et of the simulation model 10 (fiber reinforced resin molded body) were calculated in the same manner as in Example A1.

(Example B3)
Except for changing the tensile elastic modulus Er of the matrix resin 12 to 6 GPa, the tensile elastic modulus E and the theoretical tensile elastic modulus Et of the simulation model 10 (fiber reinforced resin molded body) were calculated in the same manner as in Example A1.

(Example C1)
The tensile elastic modulus Er of the matrix resin 12 is changed to 8 GPa, and the fiber length L of the carbon fiber 14 is 1750 (the length of the simulation model 10: 3501, the fiber length Lf of the carbon fiber in the actual fiber reinforced resin molding: 24. Except for the change to equivalent to 5 mm, the tensile modulus E and the theoretical tensile modulus Et of the simulation model 10 (fiber reinforced resin molded body) were calculated in the same manner as in Example A1.

(Example C2)
The tensile elastic modulus Er of the matrix resin 12 is changed to 8 GPa, and the fiber length L of the carbon fiber 14 is 2500 (the length of the simulation model 10: 5001, the fiber length Lf of the carbon fiber in the actual fiber reinforced resin molded product: 35. Except for changing to 0 mm equivalent), the tensile elastic modulus E and the theoretical tensile elastic modulus Et of the simulation model 10 (fiber reinforced resin molded body) were calculated in the same manner as in Example A1.

(Example C3)
Except for changing the tensile elastic modulus Er of the matrix resin 12 to 8 GPa, the tensile elastic modulus E and the theoretical tensile elastic modulus Et of the simulation model 10 (fiber reinforced resin molded body) were calculated in the same manner as in Example A1.

The results of Comparative Example A1, Example B1, and Example C1 are shown in Table 2, the results of Comparative Example A2, Example B2, and Example C2 are shown in Table 3, and the results of Example A1, Example B3, and Example C3 are shown. The results are summarized in Table 4.
This is a result of fixing the tensile elastic modulus Er of the carbon fiber 14 and the fiber length Lf of the carbon fiber 14 and shaking the tensile elastic modulus Er of the matrix resin 12. As Er was larger, the ratio E / Et of the tensile elastic modulus E and the theoretical tensile elastic modulus Et of the fiber reinforced resin molded product was greatly improved, and good mechanical properties were obtained.

  When the same carbon fiber is used, if the fiber length Lf of the carbon fiber is constant, higher rigidity is obtained as the tensile elastic modulus Er of the matrix resin is higher. In other words, if the tensile modulus Er of the matrix resin is constant, a long fiber length Lf is required. On the other hand, from the viewpoint of fluidity, the shorter the fiber length Lf of the carbon fiber, the easier it is to mold. As in Example C1, when Er / Et is large, even if the fiber length Lf of the carbon fiber is shortened, good mechanical properties can be obtained as a fiber-reinforced resin molded product. It is preferable when importance is attached to sex. That is, when Er / Et is small, it is preferable to lengthen the fiber length Lf of the carbon fiber, and when Er / Et is large, it is preferable to shorten the fiber length Lf of the carbon fiber. These preferable ranges are expressed by the product of Er / Et and Lf, and are 0.2 to 0.8 from the results of the examples and comparative examples.

  The fiber reinforced resin material of the present invention is useful as an SMC or the like that is an intermediate material used in the production of a fiber reinforced resin molded article.

  10 simulation model, 12 matrix resin, 14 carbon fiber.

Claims (3)

A plurality of carbon fibers, and a resin material containing one or both of a thermosetting resin and a thermoplastic resin,
Ratio of tensile elastic modulus Er (GPa) of the resin material to the tensile elastic modulus Ef (GPa) of the carbon fiber (however, when the thermosetting resin is included, the thermosetting resin is cured) Er / A fiber reinforced resin material having a product Lf × Er / Ef of Ef and a fiber length Lf (mm) of the carbon fiber in a range of 0.2 to 0.8.   The fiber reinforced resin material according to claim 1, wherein a volume content of the carbon fiber is 20% by volume or more and less than 65% by volume in 100% by volume of the fiber reinforced resin material.   A fiber-reinforced resin molded article obtained by molding the fiber-reinforced resin material according to claim 1.

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