JP5995150B2 - Carbon fiber composite material - Google Patents

Description

  The present invention relates to a carbon fiber composite material, and relates to a carbon fiber composite material that can achieve high mechanical properties and impact strength.

  Carbon fiber composite materials composed of carbon fibers and thermoplastic resins are used in the manufacture of various molded products, and various proposals have been made for the purpose of achieving high mechanical properties and impact strength of the manufactured molded products. ing. For example, Patent Document 1 proposes a composite material in which the ratio of a specific carbon fiber bundle in a carbon fiber composite material to the total amount of fibers is kept low, and the average number of fibers in the specific carbon fiber bundle is in a specific range. Yes.

  However, the carbon fiber composite material in which the carbon fiber bundle in the carbon fiber composite material is thin and the percentage of the bundle is small and the carbon fiber is opened as described in Patent Document 1 is molded using the same. Since the carbon fibers, which are the reinforcing fibers of the product, are sufficiently dispersed, it is difficult for stress to concentrate, and the reinforcing effect of the carbon fibers is sufficiently exhibited and the mechanical properties are excellent, but the impact strength is poor.

  On the other hand, in Patent Document 2, the ratio of the same specific carbon fiber bundle in the carbon fiber composite material to the total amount of fibers is set higher, and the average number of fibers in the specific carbon fiber bundle is set in another specific range. A composite material has been proposed. However, a carbon fiber composite material having a thick carbon fiber bundle and a large proportion of the bundle as described in Patent Document 2 is excellent in impact strength, but has low mechanical properties and large variations. This is because stress is easily concentrated on the end of the carbon fiber because there are many thick carbon fiber bundles.

JP 2011-178890 A JP 2011-178891 A

  An object of the present invention is to provide a carbon fiber composite material that can achieve both high mechanical properties and impact strength, which cannot be achieved by the conventional carbon fiber composite material as described above.

In order to solve the above problems, the carbon fiber composite material according to the present invention is composed of carbon fiber and a thermoplastic resin, and Mn / (Ln × D) is 8.5 × 10 ⁻¹ (mg / mm ² ) or more. The ratio Y of the carbon fiber bundle (1) to the total weight of the carbon fibers is
5 ≦ Y <30 (wt%)
The average value X of Mn / Ln of the carbon fiber bundle (1) is
3.6 × 10 ⁻² ≦ X ≦ 3.1 × 10 ⁻¹ (mg / mm)
Range near the is, and the standard deviation of the number of fibers x _n = Mn / constituting the bundle of carbon fiber bundle (1) (Ln × F) σ is,
350 ≦ σ ≦ 1000
It consists of what is characterized by existing in the range .
Mn: Carbon fiber bundle weight Ln: Carbon fiber fiber length D: Carbon fiber fiber diameter
F: Fineness of carbon fiber

  In such a carbon fiber composite material according to the present invention, when the carbon fiber bundle (1) satisfies the range specified in the present invention, high mechanical properties of a molded product using the carbon fiber bundle (1) can be realized. At the same time, excellent impact strength can be achieved.

In the carbon fiber composite material according to the present invention, high mechanical properties, in order to more surely achieve impact strength, as described above, the number of fibers constituting the bundle of carbon fiber bundle (1) x _n = Mn / area by the near of the standard deviation sigma is 350 ≦ σ ≦ 1000 of (Ln × F). F is the fineness of the carbon fiber, and the calculation method of the number of fibers x _n and the standard deviation σ will be described later.

Furthermore, in order to realize high mechanical properties and impact strength more reliably, the average value X of Mn / Ln of the carbon fiber bundle (1) is 3.6 × 10 ⁻² ≦ X ≦ 2.0 × 10. ^-1 (mg / mm)
It is preferable that it exists in the range.

In order to realize high mechanical properties and impact strength more reliably, the ratio Y of the carbon fiber bundle (1) to the total carbon fiber weight is
10 ≦ Y <30 (wt%)
It is preferable that it exists in the range.

  Moreover, in order to implement | achieve especially high impact strength, it is preferable that the fiber length Ln of the carbon fiber in the said carbon fiber bundle (1) exists in the range of 10-70 mm.

In order to realize high mechanical properties and excellent impact strength, the single fiber bending rigidity of the carbon fiber constituting the carbon fiber bundle (1) is 1.0 × 10 ^{−11 to} 2.8 × 10 ^−11. It is preferably within the range of (Pa · m ⁴ ).

Furthermore, in order to stably realize high mechanical properties and impact strength, the carbon fiber aggregate in the carbon fiber composite material is preferably made of a carbon fiber nonwoven fabric obtained by a carding process.

In addition, since a molded product having portions with different yields and thicknesses of carbon fibers can be easily produced, the carbon fiber composite material is a stampable in which a carbon fiber aggregate in the carbon fiber composite material is impregnated with a thermoplastic resin. It preferably consists of a sheet.

  Thus, according to the carbon fiber composite material according to the present invention, it is possible to provide a carbon fiber composite material excellent in both mechanical properties and impact resistance strength.

It is a schematic block diagram which shows an example of a carding apparatus.

Hereinafter, embodiments of the present invention will be described in detail.
First, the carbon fiber used in the present invention is not particularly limited, but high-strength, high-modulus carbon fibers can be used, and these may be used alone or in combination of two or more. Among these, PAN-based, pitch-based, rayon-based carbon fibers and the like can be mentioned. From the viewpoint of the balance between the strength and elastic modulus of the obtained molded product, PAN-based carbon fibers are more preferable. The density of the carbon fiber is preferably one of 1.65~1.95g / cm ^3, further more preferably from 1.70~1.85g / cm ^3. If the density is too high, the resulting carbon fiber reinforced plastic is inferior in light weight performance, and if it is too low, the mechanical properties of the resulting carbon fiber reinforced plastic may be low.

  The fiber length of the carbon fiber can be used within a range of 10 to 100 mm, and particularly preferably within a range of 10 to 70 mm.

  The carbon fibers are preferably bundles from the viewpoint of productivity, and those having a large number of single yarns in the bundle are preferred. The number of single yarns in the case of a carbon fiber bundle can be used in the range of 1000 to 350,000, and is preferably used in the range of 10,000 to 100,000.

The single fiber bending stiffness of the carbon fiber is preferably in the range of 1.0 × 10 ^{−11 to} 2.8 × 10 ⁻¹¹ Pa · m ⁴ , more preferably 1.0 × 10 ^{−11 to} 1.5. is preferable in × ¹⁰ -11 Pa · ^{m 4.} When the single yarn bending rigidity is within the above range, the quality of the obtained carbon fiber aggregate can be stabilized in the process of producing the carbon fiber aggregate described later.

  The carbon fiber is preferably surface-treated for the purpose of improving the adhesion between the carbon fiber and the matrix resin. Examples of surface treatment methods include electrolytic treatment, ozone treatment, and ultraviolet treatment. In addition, a sizing agent may be added to the carbon fiber for the purpose of preventing the fluff of the carbon fiber, improving the convergence of the carbon fiber, or improving the adhesion between the carbon fiber and the matrix resin. . Although it does not specifically limit as a sizing agent, The compound which has functional groups, such as an epoxy group, a urethane group, an amino group, and a carboxyl group, can be used, These may use 1 type or 2 types or more together.

  Further, as a sizing treatment, a liquid containing a sizing agent after sizing agent is dried after drying a water-wet carbon fiber bundle having a moisture content of about 20 to 80% by weight wetted by water in a generally known surface treatment step and washing step (sizing step). (Liquid).

  There are no particular restrictions on the means for applying the sizing agent, but there are, for example, a method of immersing in a sizing liquid through a roller, a method of contacting a roller to which the sizing liquid is adhered, and a method of spraying the sizing liquid in a mist form. . Moreover, although either a batch type or a continuous type may be sufficient, the continuous type which has good productivity and small variations is preferable. At this time, it is preferable to control the sizing solution concentration, temperature, yarn tension, and the like so that the amount of the sizing agent active ingredient attached to the carbon fiber is uniformly attached within an appropriate range. Moreover, it is more preferable to vibrate the carbon fiber with ultrasonic waves when applying the sizing agent.

  Although the drying temperature and drying time should be adjusted according to the amount of the compound attached, the time required for complete removal of the solvent used for applying the sizing agent and drying is shortened, while the thermal deterioration of the sizing agent is prevented, and carbon From the viewpoint of preventing the fiber bundle from becoming hard and deteriorating the spreadability of the bundle, the drying temperature is preferably 150 ° C. or higher and 350 ° C. or lower, and more preferably 180 ° C. or higher and 250 ° C. or lower. .

  The sizing agent adhesion amount is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 5% by mass or less, and more preferably 0.1% by mass or more and 5% by mass with respect to the mass of the carbon fiber alone. % Or less is more preferable. If it is 0.01% by mass or less, the effect of improving adhesiveness is hardly exhibited. If it is 10% by mass or more, the physical properties of the molded product may be lowered.

  In the present invention, a thermoplastic resin is used as the matrix resin. However, the material of the thermoplastic matrix resin is not particularly limited, and can be appropriately selected within a range that does not significantly reduce the mechanical properties of the carbon fiber reinforced plastic. For example, polyolefin resins such as polyethylene and polypropylene, polyamide resins such as nylon 6, nylon 6,6, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyether ketone, polyether sulfone, aromatic polyamide, etc. These resins can be used. For example, the thermoplastic matrix resin is preferably at least one selected from the group consisting of polyamide, polyphenylene sulfide, polypropylene, polyether ether ketone, and phenoxy resin.

  Examples of the process for obtaining the carbon fiber aggregate include carding and airlaid. Carding as used in the present invention refers to an operation of aligning discontinuous fibers or opening fibers by applying a force in approximately the same direction in a comb-like discontinuous fiber assembly. Say. Generally, it is carried out using a carding apparatus having a roll having a large number of needle-like projections on the surface and / or a roll around which a metallic wire having a saw-like projection of a saw is wound.

  In carrying out such carding, it is preferable to shorten the time (residence time) in which the carbon fiber is present in the carding apparatus in order to prevent the carbon fiber from being broken. Specifically, it is preferable to transfer the carbon fiber present on the wire wound around the cylinder roll of the carding apparatus to the doffer roll in as short a time as possible. Therefore, in order to promote such a transition, the rotation speed of the cylinder roll is preferably rotated at a high rotation speed such as 150 rpm or more. For the same reason, the surface speed of the doffer roll is preferably a high speed such as 10 m / min or more.

  The process for carding the carbon fiber bundle is not particularly limited, and a general one can be used. For example, as shown in FIG. 1, the carding apparatus 1 includes a cylinder roll 2, a take-in roll 3 provided on the upstream side near the outer peripheral surface, and a downstream side opposite to the take-in roll 3. And a plurality of worker rolls provided close to the outer peripheral surface of the cylinder roll 2 between the take-in roll 3 and the doffer roll 4. 5, a stripper roll 6 provided close to the worker roll 5, a feed roll 7 and a belt conveyor 8 provided close to the take-in roll 3.

  A discontinuous carbon fiber bundle 9 is supplied to the belt conveyor 8, and the carbon fiber bundle 9 is introduced onto the outer peripheral surface of the cylinder roll 2 through the outer peripheral surface of the feed roll and then the outer peripheral surface of the take-in roll 3. Up to this stage, the carbon fiber bundle is unwound and becomes an aggregate of cotton-like carbon fiber bundles. A part of the aggregate of cotton-like carbon fiber bundles introduced on the outer peripheral surface of the cylinder roll 2 is wound around the outer peripheral surface of the worker roll 5, and this carbon fiber is peeled off by the stripper roll 6 and again the cylinder roll. 2 is returned to the outer peripheral surface. A large number of needles and protrusions are present on the outer peripheral surface of each of the feed roll 7, the take-up roll 3, the cylinder roll 2, the worker roll 5 and the stripper roll 6, and the carbon fiber is The bundle is opened to a predetermined bundle by the action of the needle and oriented to some extent. Through this process, the fiber bundle is opened to a predetermined carbon fiber bundle, and moves on the outer peripheral surface of the doffer roll 4 as a sheet-like web 10 which is one form of the carbon fiber aggregate.

  Moreover, there is no restriction | limiting in particular also about airlaid, A general thing can be used. This airlaid is a method in which a cut carbon fiber bundle alone or a cut carbon fiber bundle and a thermoplastic resin fiber are introduced into a pipe and compressed air is blown to open the fiber bundle, or the fiber bundle is physically separated by a pin cylinder or the like. This is a step of obtaining a carbon fiber aggregate that has been opened, diffused and fixed by a method of opening.

  In addition, the carbon fiber aggregate referred to herein refers to a carbon fiber bundle that retains its shape due to entanglement and friction between fibers in a state where discontinuous carbon fiber bundles are opened and oriented by the carding and airlaid. A thin sheet-like web or a non-woven fabric obtained by laminating and adhering webs as necessary can be exemplified. The obtained carbon fiber aggregate is preferably obtained by carding from the viewpoint of the uniformity of the aggregate, and is preferably obtained by airlaid from the viewpoint of preventing the carbon fiber from being bent or bent.

  The carbon fiber aggregate may be composed only of carbon fibers, but can also contain thermoplastic resin fibers. It is preferable to add a thermoplastic resin fiber because the carbon fiber can be prevented from being broken in the carding and airlaid processes. Since carbon fiber is rigid and brittle, it is difficult to be entangled and easily broken. Therefore, there is a problem that a carbon fiber aggregate composed only of carbon fibers is easily cut during the production or the carbon fibers are easily dropped. Therefore, a carbon fiber aggregate with high uniformity can be formed by including thermoplastic resin fibers that are flexible, difficult to break, and easily entangled. In the present invention, when the carbon fiber aggregate contains thermoplastic resin fibers, the carbon fiber content in the carbon fiber aggregate is preferably 20 to 95 mass%, more preferably 50 to 95 mass%, More preferably, it is 70-95 mass%. If the proportion of carbon fibers is low, it will be difficult to obtain high mechanical properties when a carbon fiber composite material is used. Conversely, if the proportion of thermoplastic resin fibers is too low, the uniformity of the above-mentioned carbon fiber aggregate will be improved. The effect is not obtained.

The carbon fiber bundle in the carbon fiber aggregate is composed of carbon fiber bundle (1) and Mn / (Ln ×) in which the Mn / (Ln × D) of the carbon fiber bundle is 8.5 × 10 ⁻¹ (mg / mm ² ) or more. D) is composed of a single yarn or carbon fiber bundle of less than 8.5 × 10 ⁻¹ (mg / mm ² ), and the ratio Y of the carbon fiber bundle (1) to the total weight of the carbon fiber is
5 ≦ Y <30 (wt%)
By being in this range, it is possible to obtain a carbon fiber composite material that can achieve both mechanical properties and impact strength.
Mn: Carbon fiber bundle weight Ln: Carbon fiber fiber length D: Carbon fiber fiber diameter

The ratio Y is preferably in a range satisfying 10 ≦ Y <30 (wt%), and more preferably in a range satisfying 10 ≦ Y ≦ 28. When the ratio Y is less than 5 wt%, the impact strength is deteriorated. When the ratio Y exceeds 30, the mechanical characteristics are deteriorated and the variation in mechanical characteristics is increased.

The average value X of Mn / Ln of the carbon fiber bundle (1) in the carbon fiber assembly is
3.6 × 10 ⁻² ≦ X ≦ 3.1 × 10 ⁻¹ (mg / mm)
By satisfying the range, a carbon fiber composite material having both mechanical properties and impact strength can be obtained.

The average value X of Mn / Ln is preferably 3.6 × 10 ⁻² ≦ X ≦ 2.0 × 10 ⁻¹ (mg / mm), and more preferably 3.6 × 10 ⁻² ≦ X ≦. 1.5 × 10 ⁻¹ (mg / mm). If the average value X of Mn / Ln is less than 3.6 × 10 ⁻² , the impact strength is deteriorated. When the average value X of Mn / Ln exceeds 2.0 × 10 ⁻¹ , the mechanical characteristics are deteriorated, and the dispersion of the mechanical characteristics is increased.

The standard deviation σ of the number of carbon fibers _xn constituting the carbon fiber bundle described later of the carbon fiber bundle (1) in the carbon fiber aggregate satisfies the range of 350 ≦ σ ≦ 1000, and the carbon fiber bundle is dispersed in the above range. Therefore, both mechanical properties and impact strength can be achieved. When the standard deviation σ is less than 350, the impact strength is lowered. When the standard deviation σ is more than 1000, the mechanical characteristics are deteriorated and the variation in mechanical characteristics is also increased. here,
x _n = Mn / (Ln × F), where F is the fineness of the carbon fiber.

The standard deviation σ is preferably 350 ≦ σ ≦ 800, and more preferably 400 ≦ σ ≦ 700.

  In the present invention, when the thermoplastic fiber is included in the carbon fiber aggregate, the fiber length of the thermoplastic resin fiber is within a range in which the object of the present invention can be achieved such as maintaining the shape of the carbon fiber aggregate and preventing the carbon fiber from falling off. If there is no particular limitation, thermoplastic resin fibers of about 10 to 100 mm can be generally used. In addition, the fiber length of the thermoplastic resin fiber can be relatively determined according to the fiber length of the carbon fiber. For example, when a carbon fiber aggregate is stretched, a larger tension is applied to the fiber having a long fiber length. Therefore, if the carbon fiber is to be tensioned and oriented in the length direction of the carbon fiber aggregate, the carbon fiber aggregate The fiber length can be made longer than the fiber length of the thermoplastic resin fiber, and in the opposite case, the fiber length of the carbon fiber can be made shorter than the fiber length of the thermoplastic resin fiber.

  Moreover, it is preferable to provide crimp to the thermoplastic resin fiber for the purpose of enhancing the entanglement effect by the thermoplastic resin fiber. The degree of crimp is not particularly limited as long as the object of the present invention can be achieved. Generally, thermoplastic resin fibers having a number of crimps of about 5 to 25 crests / 25 mm and a crimping ratio of about 3 to 30%. Can be used.

  There is no restriction | limiting in particular as a material of this thermoplastic resin fiber, It can select suitably in the range which does not reduce the mechanical characteristic of a carbon fiber composite material significantly. For example, polyolefin resins such as polyethylene and polypropylene, polyamide resins such as nylon 6, nylon 6,6, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyether ketone, polyether sulfone, aromatic polyamide, etc. A fiber obtained by spinning a resin of the above can be used. It is preferable that the material of the thermoplastic resin fiber is appropriately selected and used depending on the combination of matrix resins. In particular, a thermoplastic resin fiber using the same resin as the matrix resin, a resin compatible with the matrix resin, or a resin having high adhesiveness with the matrix resin is preferable because it does not deteriorate the mechanical properties of the carbon fiber reinforced plastic. For example, the thermoplastic resin fiber is preferably at least one fiber selected from the group consisting of polyamide fiber, polyphenylene sulfide fiber, polypropylene fiber, polyether ether ketone fiber and phenoxy resin fiber.

  In the present invention, when impregnating the carbon fiber aggregate with the matrix resin, a carbon fiber aggregate containing thermoplastic resin fibers is prepared, and the thermoplastic resin fibers contained in the carbon fiber aggregate are used as they are as the matrix resin. Alternatively, the carbon fiber aggregate not containing the thermoplastic resin fiber may be used as a raw material, and the matrix resin may be impregnated at any stage of producing the carbon fiber composite material. Further, even when a carbon fiber aggregate containing thermoplastic resin fibers is used as a raw material, the matrix resin can be impregnated at any stage of producing the carbon fiber composite material. In such a case, the resin constituting the thermoplastic resin fiber and the matrix resin may be the same resin or different resins. When the resin constituting the thermoplastic resin fiber is different from the matrix resin, it is preferable that both have compatibility or higher affinity.

  When the carbon fiber composite material is manufactured, the carbon fiber aggregate as described above is impregnated with a thermoplastic resin as a matrix resin, and the impregnation step to make the carbon fiber composite material is performed using a press machine having a heating function. Can do. The press machine is not particularly limited as long as it can realize the temperature and pressure necessary for impregnation with the matrix resin, and a normal press machine having a flat platen that moves up and down, and a mechanism in which a pair of endless steel belts travel. A so-called double belt press machine having the following can be used. In such an impregnation step, the matrix resin can be formed into a sheet shape such as a film, a nonwoven fabric, or a woven fabric, and then laminated with a carbon fiber aggregate, and in that state, the matrix resin can be melted and impregnated using the press machine or the like. In addition, discontinuous fibers are produced using a matrix resin, and mixed with inorganic fibers in the process of producing the carbon fiber aggregate, thereby producing a carbon fiber aggregate containing the matrix resin and the inorganic fibers. A method of heating and pressurizing the aggregate using a press machine or the like can also be employed.

  Whether it is within the range specified by the present invention as described above can be determined by the following measurement method.

(1) Measuring method of bundle

A sample of 100 mm × 100 mm was cut out from the carbon fiber composite material, and then the sample was heated for about 1 hour in an electric furnace heated to 500 ° C. to burn off organic substances such as matrix resin. After measuring the mass of the carbon fiber aggregate remaining after cooling to room temperature, all the carbon fiber bundles were extracted from the carbon fiber aggregate with tweezers. About all the extracted carbon fiber bundles, weight Mn and length Ln of each carbon fiber bundle are measured using a balance capable of measuring up to 1/10000 g. After the measurement, Mn / Ln, Mn / (Ln × D), and x _n = Mn / (Ln × F) are calculated for each bundle. Here, D is the carbon fiber diameter, F is the fineness of the carbon fiber, and x _n is the number of constituent fibers of the carbon fiber bundle. Mn / the (Ln × D) value 8.5 × 10 ^-1 mg / mm ² or more fiber bundles of the carbon fiber bundle (1), the total weight of the carbon fiber bundle (1) and _{M A,} flux Total N is measured. Further, the carbon fiber bundle under 8.5 × 10 ^-1 mg / mm ² and the fiber bundle (2), the total weight of the carbon fiber bundle (2) as _{M B,} measured. Fiber bundles opened to such an extent that they cannot be extracted with tweezers were collectively measured and finally weighed. Further, when the fiber length is short and it becomes difficult to measure the weight, the fiber length is classified at intervals of about 0.2 mm, the weight is measured for a bundle of a plurality of classified bundles, and an average value may be used. . After all classification and measurement, for the carbon fiber bundle (1), Σ (Mn / Ln) / N, x = Σ {Mn / (Ln × F)} / N, σ = {1 / N × Σ (x _n− x) ² } ^1/2 is calculated, and the average value X of Mn / Ln of the carbon fiber bundle (1), the average value x of the number of constituent fibers of the fiber bundle, and the standard deviation σ of the number of constituent fibers of the fiber bundle are calculated. Ask. N is the total number of bundles of carbon fibers (1). The ratio of the carbon fiber bundle (1) to the total weight of the carbon fiber bundle is
_{M A / (M A + M} B) × 100
Sought by.

(2) Vf (carbon fiber content in carbon fiber reinforced plastic)
About 2 g of a sample was cut out from a molded product of carbon fiber reinforced plastic, and its mass was measured. Thereafter, the sample was heated in an electric furnace heated to 500 ° C. for 1 hour to burn off organic substances such as a matrix resin. After cooling to room temperature, the mass of the remaining carbon fiber was measured. The ratio of the mass of the carbon fiber to the mass of the sample before the organic substance such as the matrix resin was burned off was measured to obtain the carbon fiber content.

(3) Single yarn bending stiffness (Pa · m ⁴ )
Single yarn bending stiffness = E × I
Calculated by here,
E: Single yarn elastic modulus
I: Section moment of inertia.
Assuming that the fiber cross-section is a perfect circle, the cross-sectional secondary moment was obtained from the fiber diameter D, and the bending stiffness was obtained from the single yarn tensile elastic modulus and the cross-sectional secondary moment.

(4) Charpy impact strength (notched)
The notched impact strength of the carbon fiber composite material was determined according to JISK 7111-1.

Used carbon fiber bundle (A):
A continuous carbon fiber bundle (A) having a fiber diameter of 7 μm, a tensile elastic modulus of 230 GPa, a single yarn bending rigidity of 2.71 × 10 ⁻¹¹ Pa · m ⁴ , and 12,000 filaments was used.

Example 1:
The carbon fiber bundle (A) is cut to a fiber length of 15 mm, and the cut carbon fiber bundle and nylon 6 short fiber (short fiber fineness 1.7 dtex, cut length 51 mm, crimp number 12 peaks / 25 mm, crimp rate 15%) Were mixed at a mass ratio of 90:10 and charged into a carding apparatus. The web that came out was cross-wrapped to form a sheet-like carbon fiber aggregate having a basis weight of 100 g / cm ² made of carbon fiber and nylon 6 fiber.

The winding direction of the sheet-like carbon fiber aggregate is 0 °, and 12 carbon fiber aggregates are laminated so as to be (0 ° / 90 ° / 0 ° / 90 ° / 0 ° / 90 °) _s. Further, a nylon resin melt blown nonwoven fabric (“CM1001”, ηr = 2.3, manufactured by Toray Industries, Inc.) is used so that the volume ratio of the carbon fiber to the thermoplastic resin is 25:75 in the entire laminated carbon fiber aggregate. After the lamination, the whole was sandwiched between stainless plates, preheated at 240 ° C. for 90 s, and hot-pressed at 240 ° C. for 180 s while applying a pressure of 2.0 MPa. Subsequently, it cooled to 50 degreeC in the pressurization state, and obtained the flat plate of the carbon fiber composite material of thickness 2mm. When the bending strength and Charpy impact strength (with notches) in the 0 ° and 90 ° directions were measured with respect to the 0 ° direction of the surface layer of the obtained flat plate, the average value of the bending strength in the 0 ° and 90 ° directions was 380 MPa. The fiber strength utilization rate was 15.2 MPa /%, and the Charpy impact strength was 40 kJ / m ² .

When the sample was cut out from the obtained flat plate and the fiber bundle was measured, the ratio Y of the carbon fiber bundle (1) to the total weight of the carbon fiber was 18 wt%, the average value X of M / L was 0.04 mg / mm, The standard deviation σ was 405. The conditions, measurements, and evaluation results are shown in Table 1.

Examples 2-5, Comparative Examples 1-2:
A flat plate of carbon fiber composite material was obtained in the same manner as in Example 1 except that the conditions were changed as shown in Table 1 for Example 1. The conditions, measurements, and evaluation results are also shown in Table 1.

  The carbon fiber composite material according to the present invention can be applied to the production of any carbon fiber reinforced molded product that requires excellent moldability, high mechanical properties, and impact strength.

DESCRIPTION OF SYMBOLS 1 Carding apparatus 2 Cylinder roll 3 Take-in roll 4 Doffer roll 5 Worker roll 6 Stripper roll 7 Feed roll 8 Belt conveyor 9 Discontinuous carbon fiber 10 Sheet-like web

Claims (6)

The ratio Y of the carbon fiber bundle (1) consisting of carbon fibers and a thermoplastic resin and having a Mn / (Ln × D) of 8.5 × 10 ⁻¹ (mg / mm ² ) or more to the total weight of the carbon fibers is
5 ≦ Y <30 (wt%)
The average value X of Mn / Ln of the carbon fiber bundle (1) is
3.6 × 10 ⁻² ≦ X ≦ 3.1 × 10 ⁻¹ (mg / mm)
Range near the is, and the standard deviation of the number of fibers x _n = Mn / constituting the bundle of carbon fiber bundle (1) (Ln × F) σ is,
350 ≦ σ ≦ 1000
A carbon fiber composite material characterized by being in the range .
Mn: Carbon fiber bundle weight Ln: Carbon fiber fiber length D: Carbon fiber fiber diameter
F: Fineness of carbon fiber The average value X of Mn / Ln of the carbon fiber bundle (1) is
3.6 × 10 ⁻² ≦ X ≦ 2.0 × 10 ⁻¹ (mg / mm)
In the range of the carbon fiber composite material according to claim 1. The ratio Y of the carbon fiber bundle (1) to the total carbon fiber weight is
10 ≦ Y <30 (wt%)
The carbon fiber composite material according to claim 1 or 2 in the range of. The carbon fiber composite material according to any one of claims 1 to 3 , wherein a fiber length Ln of carbon fibers in the carbon fiber bundle (1) is in a range of 10 to 70 mm. The single yarn bending stiffness of the carbon fibers constituting the carbon fiber bundle (1) is in the range of ^{1.0 × 10 -11 ~2.8 × 10 -11} (Pa · m 4), according to claim 1-4 The carbon fiber composite material according to any one of the above. The carbon fiber composite material according to any one of claims 1 to 5 , wherein the carbon fiber composite material comprises a stampable sheet obtained by impregnating a carbon fiber aggregate in the carbon fiber composite material with a thermoplastic resin.

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