Composite material, prepreg, carbon fiber reinforced molded product, and method for producing composite material

Patent metadata

Field	Value
Publication number	US-12060468-B2
Application number	US-201915734624-A
Country	US
Kind code	B2
Filing date	Jun 10, 2019
Priority date	Jun 11, 2018
Publication date	Aug 13, 2024
Grant date	Aug 13, 2024

Abstract

Provided are a composite material capable of further enhancing property derived from carbon nanotubes adhered to carbon fibers, a prepreg, a carbon-fiber-reinforced molded article, and a method for manufacturing a composite material. There is provided a composite material including: carbon fibers; and a structure which includes a plurality of carbon nanotubes and has a network structure in which the carbon nanotubes are in direct contact with each other, and in which the carbon nanotubes adhered to surfaces of the carbon fibers directly adhere to the surfaces of the carbon fibers. The carbon nanotubes have a bent shape having a bent portion.

First claim

The invention claimed is:

1. A composite material comprising:
carbon fibers; and
a structure which includes by a plurality of carbon nanotubes and has a network structure in which the carbon nanotubes are in direct contact with each other, and in which the carbon nanotubes adhered to surfaces of the carbon fibers directly adhere to the surfaces of the carbon fibers,
wherein each of the carbon nanotubes has a length within a range of 0.1 to 10 μm, and the carbon nanotubes have a bent shape having a bent portion,
the structure has a structure in which the plurality of carbon nanotubes are knitted like a non-woven fabric fiber, and
a weight ratio that is a ratio of the weight of the carbon nanotubes adhered to the carbon fibers to the weight of the carbon fibers is within a range of 0.001 to 0.01, and a standard deviation of the weight ratio in a range of 1 m in a length of the carbon fibers is 0.0005 or less.

2. The composite material according to claim 1 , further comprising:
a plurality of fixing resin parts which partially fix some of the carbon nanotubes to the surfaces of the carbon fibers, the plurality of fixing resin parts being formed by curing a resin into particles reaching the surface of the carbon fibers from a surface of the structure,
wherein on a surface of the structure in plan view, an area ratio of the plurality of fixing resin parts which cover the surface of the structure is within a range of 6% to 45%.

3. The composite material according to claim 2 ,
wherein the number of the fixing resin parts per 5 μm square on the surface of the structure in plan view is within a range of 27 to 130.

4. The composite material according to claim 1 ,
wherein a thickness of the structure is within a range of 10 to 300 nm.

5. The composite material according to claim 1 ,
wherein each of the carbon nanotubes has a diameter within a range of 1 to 15 nm.

6. The composite material according to claim 1 ,
wherein a carbon fiber bundle is formed by a plurality of the carbon fibers which are continuous, and
the structure is formed on each of the carbon fibers of the carbon fiber bundle.

7. The composite material according to claim 6 ,
wherein the structure formed on each of the plurality of carbon fibers has an independent structure, and the structure of one of the carbon fibers does not share its carbon nanotubes with the structure of another carbon fiber.

8. A method for manufacturing the composite material according to claim 1 , comprising:
applying ultrasonic vibration to a dispersion in which a plurality of carbon nanotubes in a bent shape having a bent portion are dispersed; and
immersing a carbon fiber bundle including a plurality of continuous carbon fibers while opening in the dispersion to which the ultrasonic vibration is applied, causing the plurality of carbon nanotubes to adhere to the carbon fibers to form a structure on a surface of each of the carbon fibers,
wherein a frequency of the ultrasonic vibration is within a range of 200 to 950 kHz, and
a relationship of Ts≥65,000/fs is satisfied, where fs represents a frequency of the ultrasonic vibration, and Ts second represents immersion time for which a part of the carbon fiber bundle to which the carbon nanotubes adhere, which is immersed in the dispersion.

9. The method for manufacturing the composite material according to claim 8 , further comprising:
forming a plurality of fixing resin parts which partially fix some of the carbon nanotubes of the structure to the surface of the carbon fiber by bringing the carbon fiber bundle that is opened into contact with a treatment liquid obtained by dispersing an uncured resin in a dispersion medium, and evaporating the dispersion medium from the carbon fiber bundle and curing the resin, wherein the plurality of fixing resin parts are formed by curing a resin into particles reaching the surface of the carbon fibers from a surface of the structure.

10. A prepreg comprising:
the composite material according to claim 6 ; and
a matrix resin in a state of being impregnated into the composite material.

11. A carbon-fiber-reinforced molded article comprising:
the composite material according to claim 6 ; and
a matrix resin that is cured in a state of being impregnated into the composite material.

12. A carbon-fiber-reinforced molded article comprising:
the composite material according to claim 6 ; and
a matrix resin that is cured in a state of being impregnated into the composite material,
wherein on the basis of a bending elastic modulus that is measured at a test speed of 5 mm/minute in a three-point bending test conforming to JIS K 7074:1988 by using a test piece having a plate shape which has a length of 100 mm, a width of 15 mm, and a thickness of 1.8 mm, and in which a width direction matches a fiber axis direction of the carbon fibers, an increasing rate of a bending elastic modulus that is measured under the same condition by setting a test speed of 1,000 mm/second is 2% or less.

13. A carbon-fiber-reinforced molded article comprising:
the composite material according to claim 6 ; and
a matrix resin that is cured in a state of being impregnated into the composite material,
wherein a logarithmic decrement in an amplitude is 0.029% or more, the amplitude being obtained from the amount of displacement of the other end of a test piece that has a plate shape which has a length of 200 mm, a width of 15 mm, and a thickness of 1.8 mm and in which a longitudinal direction matches a fiber axis direction of the carbon fibers, and is horizontally fixed by clamping one end in a length range of 50 mm in the longitudinal direction, and the amount of displacement being measured after pressing the other end of the test piece and releasing the other end of the test piece.

14. A carbon-fiber-reinforced molded article comprising:
the composite material according to claim 6 ; and
a matrix resin that is cured in a state of being impregnated into the composite material,
wherein when performing a pulsating three-point bending fatigue test in which pressing against a test piece having a plate shape which has a length of 20 mm, a width of 15 mm, and a thickness of 1.8 mm and in which a width direction matches a fiber axis direction of the carbon fibers from an upward side and release of the pressing are repeated in a state of supporting the test piece from a lower side with a pair of supporting points disposed to be spaced apart from each other by 20 mm in a longitudinal direction of the test piece, the number of times of repetition of pressing until a load at the time of pressing performed when a stress amplitude is within a range of 1,100 to 1,300 MPa reaches zero is within a range of 92,000 to 1,000,000.

Assignees

• Nitta Corp

Inventors

• Komukai Takuji
• Onizuka Maki
• Teruhira Hiromi

Classifications

• Y10T428/2927

  including structurally defined particulate matter · CPC title

• Y10T428/292

  In coating or impregnation · CPC title

• Y10T428/25

  Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles · CPC title

• Y10T428/2922

  Nonlinear [e.g., crimped, coiled, etc.] · CPC title

• Y10T428/249948

  Fiber is precoated · CPC title