Composite base material
There is provided a composite base material, including: carbon fibers having an average fiber length of 3 mm or more and 100 mm or less; and a thermoplastic resin is firmly fixed to the carbon fibers in an amount of 3 to 100 parts by mass with respect to 100 parts by mass of the carbon fibers, wherein a void ratio is more than 7 vol % to less than 100 vol %.
1. A composite base material, comprising:
carbon fibers having an average fiber length of 3 mm or more and 100 mm or less; and
a thermoplastic resin is firmly fixed to the carbon fibers in an amount of 3 to 100 parts by mass with respect to 100 parts by mass of the carbon fibers,
wherein a void ratio of the composite base material is more than 7 vol % to less than 100 vol %,
wherein a width of the carbon fibers is 5 mm or less and a thickness of the carbon fibers is ½ or less of the width, and
wherein the carbon fibers are in a mat-form material in which the carbon fibers are two-dimensionally randomly oriented and no carbon fibers are aligned in one direction on a surface thereof.
2. The composite base material according to claim 1 ,
wherein the composite base material is obtained by heating and pressurizing a mat-form material in which a carbon fiber mat and a thermoplastic resin are combined, and
the composite base material is obtained by applying heat and pressure so that a decrease in the void ratio does not exceed 40 vol % in one heating and pressurizing treatment.
3. The composite base material according to claim 1 ,
wherein the composite base material is obtained by heating and pressurizing a mat-form material in which a carbon fiber mat and a thermoplastic resin are combined, and
the composite base material has the void ratio of more than 7 vol % to less than 80 vol %, obtained by preparing a composite base material having a void ratio of 60 vol % or more and further heating and pressurizing the composite base material so that a decrease in the void ratio does not exceed 20 vol % in one heating and pressurizing treatment.
4. The composite base material according to claim 1 ,
wherein the composite base material is obtained by heating and pressurizing a mat-form material in which a carbon fiber mat and a thermoplastic resin are combined, and
the composite base material is a composite base material having a void ratio of from more than 7 vol % to less than 80 vol %, obtained by preparing a composite base material having a void ratio of from 40 vol % to less than 60 vol % and further heating and pressurizing the composite base material so that a decrease in the void ratio does not exceed 30 vol % in one heating and pressurizing treatment.
5. The composite base material according to claim 1 ,
wherein a carbon fiber bundle (A) constituted by the carbon fibers of not less than a critical number of single fibers, defined by the following formula (1), is present in the carbon fibers:
Critical number of single fibers=600 /D (1)
wherein D is an average fiber diameter (m) of single carbon fibers.
6. The composite base material according to claim 5 ,
wherein a ratio of the carbon fiber bundle (A) to a total amount of the carbon fibers contained in the composite base material is more than 0 vol % to less than 99 vol %.
7. The composite base material according to claim 5 ,
wherein an average number (N) of fibers in the carbon fiber bundle (A) satisfies the following formula (2):
0.7×10 4 /D 2 <N< 2×10 5 /D 2 (2)
wherein D is the average fiber diameter (μm) of single carbon fibers.
8. The composite base material according to claim 1 ,
wherein the void ratio is more than 7 vol % to less than 90 vol %.
9. The composite base material according to claim 1 ,
wherein the void ratio is more than 7 vol % to less than 40 vol %.
10. The composite base material according to claim 1 , which is a long plate-shaped material.
11. A composite material obtained by pressurizing the composite base material according to claim 1 .
12. The composite material according to claim 11 ,
wherein a void ratio of the composite material is from 0 to 7 vol %.