Composite Material Including Unidirectional Continuous Fibers and Thermoplastic Resin

Abstract

According to one example of the present invention, there is provided a composite material for cold pressing including: carbon fibers that are unidirectional continuous fibers; and a thermoplastic resin, wherein the composite material has a thickness of 0.3 mm or more, when the composite material is observed from a direction perpendicular to a continuous fiber direction, a cross section of the carbon fibers included in the composite material satisfies the following specific Expressions (1), (2) and (3): n 1/ N ≦0.1  Expression (1), p <0.01  Expression (2), and 0.001≦(1− dc /( dr *( Vr /100)+ df *( Vf /100)))≦0.1  Expression (3).

What is claimed is: 
     
         1 . A composite material for cold pressing comprising:
 carbon fibers that are unidirectional continuous fibers; and   a thermoplastic resin,   wherein the composite material has a thickness of 0.3 mm or more,   when the composite material is observed from a direction perpendicular to a continuous fiber direction, a cross section of the carbon fibers included in the composite material satisfies Expression (1), (2) and (3):
     n 1/ N≦ 0.1  Expression (1),
 
     p< 0.01  Expression (2), and
 
   0.001(1− dc /( dr *( Vr/ 100)+ df *( Vf/ 100)))≦0.1  Expression (3),
 
   wherein N represents the number of carbon fibers included in the composite material,   n1 represents the number of carbon fibers in which less than 50% of the surface is covered with at least one of the thermoplastic resin and a sizing agent,   p represents a ratio of the number of carbon fibers which are not substantially covered with any of the thermoplastic resin and the sizing agent,   Vr represents a volume ratio (%) of thermoplastic resin included in the composite material,   Vf represents a volume ratio (%) of carbon fibers included in the composite material,   dr represents a density of thermoplastic resin,   df represents a density of carbon fibers, and   dc represents a density of the composite material.   
     
     
         2 . The composite material according to  claim 1 ,
 wherein a volume ratio (VD of the carbon fibers included in the composite material is 10 Vol % or more and 70 Vol % or less.   
     
     
         3 . The composite material according to  claim 1 ,
 wherein the thickness of the composite material is 0.4 mm or more and 10.0 mm or less.   
     
     
         4 . The composite material according to  claim 1 ,
 wherein a width of the composite material is 20 mm or more and 2,000 mm or less.   
     
     
         5 . A layered body comprising:
 the composite material according to  claim 1 ; and   an isotropic base material in which discontinuous carbon fibers are randomly dispersed.   
     
     
         6 . A method of producing a shaped product comprising:
 cold-pressing the composite material according to  claim 1 ,   wherein a density dm of the shaped product satisfies
   (1− dm /( dr *( Vr/ 100)+ df *( Vf/ 100)))<(1− dc /( dr *( Vr/ 100)+ df *( Vf/ 100)))×0.8.
 
   
     
     
         7 . The method of producing a shaped product according to  claim 6 ,
 wherein the density dm of the shaped product satisfies Expression (4):
   0≦(1− dm /( dr *( Vr/ 100)+ df *( Vf/ 100)))≦0.08  Expression (4).
 
   
     
     
         8 . A method of producing the composite material according to  claim 1 , the method comprising:
 heating a composite material precursor;   adjusting a cross-sectional area of the composite material precursor including carbon fibers which are unidirectional continuous fibers and a thermoplastic resin with a jig; and   cooling the composite material precursor to produce a composite material.   
     
     
         9 . The method of producing a composite material according to  claim 8 ,
 wherein the jig is a hollow jig, and   a minimum cross-sectional area St of a hollow portion of the hollow jig satisfies Expression (5):
   ( Sf+Sr )< St <( Sf+Sr )*1.3  Expression (5)
 
   wherein Sf represents an area of carbon fibers included in the composite material when observed from the cross-sectional direction perpendicular to the continuous fiber direction, and   
       Sr represents an area of thermoplastic resin included in the composite material when observed from the cross-sectional direction perpendicular to the continuous fiber direction.