Fiber composite material and method of producing the same

1. A fiber composite material, comprising:

an elastomer;

carbon nanofibers having an average diameter of 0.7 to 15 nm and an average length of 0.5 to 100 micrometers; and

fibers having an average diameter of 1 to 100 micrometers and an aspect ratio of 50 to 500,

the carbon nanofibers and the fibers being dispersed in the elastomer, and the elastomer including an unsaturated bond or a group exhibiting affinity to the carbon nanofibers,

wherein the fiber composite material includes the carbon nanofibers in an amount of 1 to 30 vol % and the fibers in an amount of 3 to 40 vol %, and has an average coefficient of linear expansion of 100 ppm (1/K) or less and a differential coefficient of linear expansion of 120 ppm (1/K) or less at −80 to 300° C.

2. The fiber composite material as defined in claim 1 ,

wherein the fiber composite material has a ratio of a coefficient of linear expansion in an arbitrary direction X and a coefficient of linear expansion in a direction Y perpendicular to the direction X of 0.7 to 1.3 at −80 to 300° C.

3. The fiber composite material as defined in claim 1 , wherein the carbon nanofibers have an aspect ratio of 50 or more.

4. The fiber composite material as defined in claim 1 , wherein the fiber composite material is in an uncrosslinked form.

5. The fiber composite material as defined in claim 1 , wherein the fiber composite material is in a crosslinked form.

6. The fiber composite material as defined in claim 1 , wherein the elastomer has a molecular weight of 5,000 to 5,000,000.

7. The fiber composite material as defined in claim 1 ,

wherein at least one of a main chain, side chain, and terminal chain of the elastomer includes at least one unsaturated bond or group selected from a double bond, a triple bond, and a functional group.

8. The fiber composite material as defined in claim 1 ,

wherein a network component of the elastomer in an uncrosslinked form has a spin-spin relaxation time (T2n) measured at 30° C. by a Hahn-echo method using a pulsed nuclear magnetic resonance (NMR) technique of 100 to 3,000 microseconds.

9. The fiber composite material as defined in claim 1 ,

wherein a network component of the elastomer in a crosslinked form has a spin-spin relaxation time (T2n) measured at 30° C. by a Hahn-echo method using a pulsed nuclear magnetic resonance (NMR) technique of 100 to 2,000 microseconds.

10. The fiber composite material as defined in claim 1 , wherein the fibers are natural fibers.

11. The fiber composite material as defined in claim 1 , wherein the fibers are metal fibers.

12. The fiber composite material as defined in claim 1 , wherein the fibers are synthetic fibers.

13. The fiber composite material as defined in claim 1 , wherein the fiber composite material has a heat resistant temperature of 300° C. or more.

14. A method of producing a fiber composite material, the method comprising:

mixing carbon nanofibers having an average diameter of 0.7 to 15 nm and an average length of 0.5 to 100 micrometers and fibers having an average diameters of 1 to 100 micrometers and an aspect ratio of 50 to 500 into an elastomer including an unsaturated bond or a group exhibiting affinity to the carbon nanofibers; and

dispersing the carbon nanofibers and the fibers by applying a shear force,

wherein the fiber composite material includes the carbon nanofibers in an amount of 1 to 30 vol % and the fibers in an amount of 3 to 40 vol %, and has an average coefficient of linear expansion of 100 ppm (1/K) or less and a differential coefficient of linear expansion of 120 ppm (1/K) or less at −80 to 300° C.