Positive and negative poisson ratio material

Abstract

A Poisson's ratio material includes a carbon nanotube film structure. The carbon nanotube film structure includes a plurality of carbon nanotubes. A first part of the carbon nanotubes are aligned a first direction, a second part of the carbon nanotubes are aligned a second direction. The first direction is substantially perpendicular to second direction. When the Poisson's ratio material is stretched or compressed substantially along the first or second direction, a Poisson's ratio value is negative. When the Poisson's ratio material is stretched or compressed in a direction having an angle of about 45 degrees with the first direction, the Poisson's ratio value is positive.

1 . A material, comprising:
 a carbon nanotube film structure comprising at least two layers of carbon nanotube films, each carbon nanotube film having a plurality of carbon nanotubes, the carbon nanotubes in at least one of the at least two layers of carbon nanotube films aligned along a first direction, and the carbon nanotubes of at least one of the at least two layers carbon nanotube films aligned along a second direction;   wherein the first direction is substantially perpendicular to the second direction; when the Poisson's ratio material is stretched or compressed substantially along the first or second direction, a Poisson's ratio value is negative; when the Poisson's ratio material is stretched or compressed in a direction having an angle of about 45 degrees with the first direction, the Poisson's ratio value is positive.   
     
     
         2 . The material as claimed in  claim 1 , wherein the at least two layers of carbon nanotube films are stacked and combined or joined to each other by Van der Waals attractive force, to form the carbon nanotube film structure. 
     
     
         3 . The material as claimed in  claim 1 , wherein an orientation of the carbon nanotubes in the at least two layers of carbon nanotube film structure is biaxial. 
     
     
         4 . The material as claimed in  claim 1 , wherein the carbon nanotubes aligned along the first direction are crossed with the carbon nanotubes aligned along the second direction to form a plurality of grids. 
     
     
         5 . The material as claimed in  claim 1 , wherein the carbon nanotube film structure comprises 10 layers to 5000 layers of carbon nanotube films. 
     
     
         6 . A material, comprising:
 a polymer matrix; and   a carbon nanotube film structure disposed in the polymer matrix, the carbon nanotube film structure comprising a plurality of carbon nanotubes, wherein a first part of the carbon nanotubes is aligned along a first direction, a second part of the carbon nanotubes is aligned along a second direction, and the first direction is substantially perpendicular to the second direction.   
     
     
         7 . The material as claimed in  claim 6 , wherein the first part of the carbon nanotubes is stacked on the second part of the carbon nanotubes in a substantially perpendicular manner. 
     
     
         8 . The material as claimed in  claim 7 , wherein the first part of the carbon nanotubes and the second part of the carbon nanotubes are combined or joined to each other by Van der Waals attractive force, to form the carbon nanotube film structure. 
     
     
         9 . The material as claimed in  claim 6 , wherein an orientation of the plurality of carbon nanotubes of the carbon nanotube film structure is biaxial. 
     
     
         10 . The material as claimed in  claim 6 , wherein the carbon nanotube film structure comprises at least two stacked carbon nanotube films, the first part of the carbon nanotubes forms one of the at least two stacked carbon nanotube films, and the second part of the carbon nanotubes forms the other one of the at least two stacked carbon nanotube films. 
     
     
         11 . The material as claimed in  claim 10 , wherein each carbon nanotube film comprises a plurality of successive and oriented carbon nanotubes joined end to end by Van der Waals attractive force. 
     
     
         12 . The material as claimed in  claim 6 , wherein when the Poisson's ratio material is stretched or compressed in the first or second direction of the carbon nanotubes of the carbon nanotube structure, the Poisson's ratio value is negative. 
     
     
         13 . The material as claimed in  claim 6 , wherein when the Poisson's ratio material is stretched in a direction having an angle of about 45 degrees with the first or the second direction of the carbon nanotubes in the carbon nanotube structure, the Poisson's ratio value is positive. 
     
     
         14 . The material as claimed in  claim 6 , wherein the polymer matrix is made of a flexible polymer material selected from the group consisting of polydimethylsiloxane, polyurethane, epoxy resin and polymethyl-methacrylate. 
     
     
         15 . A material, comprising:
 a first characteristic direction;   a second characteristic direction substantially perpendicular to the first characteristic direction;   a third characteristic direction having an angle of about 45 degrees with the first characteristic direction;   a plurality of first films formed from a plurality of carbon nanotubes aligned in the first characteristic direction;   a plurality of second films formed from a plurality of carbon nanotubes aligned in the second characteristic direction;   wherein the first films and the second films are alternately arranged and stacked on one another and the carbon nanotubes in the first films are substantially perpendicular to the carbon nanotubes in the second films; the material shows a negative Poisson's ratio when it is stretched or compressed in the first characteristic direction or the second characteristic direction, and the Poisson's ratio material shows a positive Poisson's ratio when it is stretched or compressed in the third characteristic direction.   
     
     
         16 . The material as claimed in  claim 15 , further comprising a polymer matrix, wherein the first films and the second films are disposed in the polymer matrix.