Composite materials and structures

Abstract

The invention provides composite components, structures and method for producing composite components. A composite component has a negative effect Poisson's ratio and comprises a first component and a second component. The first component and the second component extend longitudinally relative to an axis, the first component being provided around the second component through one or more turns which are spaced longitudinally relative to the axis. A variation in the tensile load on the first component causes the radial position of the second component relative to the axis to vary.

1 . A composite component having a negative effective Poisson's ratio, the composite component including a first component and a second component, the first component and the second component extending longitudinally relative to an axis, the first component being provided around the second component through one or more turns, the one or more turns being spaced longitudinally relative to the axis, wherein variation in tensile or compressive load on the first component causing variation in radial position of the second component relative to the axis. 
     
     
         2 . A composite component according to  claim 1 , in which the first component has a higher modulus of elasticity than the second component. 
     
     
         3 . A composite component according to  claim 1  having the first component arranged around the second component in a helical manner, wherein the variation in the tensile or compressive load on the first component causing variation in the diameter of the helix of the first component, the variation in the diameter of the helix of the first component causing the second component to form a helix and/or causing variation in the diameter of the helix of the second component, so that the diameter of the second component helix increases as the diameter of the first component helix decreases and the diameter of the second component helix decreases as the diameter of the first component helix increases. 
     
     
         4 . A composite component according to  claim 1 , in which the first component is provided around the second component by applying and/or wrapping and/or covering and/or spinning. 
     
     
         5 . A composite component according to  claim 1 , in which the first component is a fibre, rod or hollow tube of a relatively high modulus material and the second component is a fibre, rod or hollow tube of an intermediate or a low modulus material compared with the first component material. 
     
     
         6 . A composite component according to  claim 1  in which the axis is provided through a core component. 
     
     
         7 . A composite component according to  claim 3 , in which the variation in radial position is an increase in displacement of at least a part of the second component relative to the axis when the load is varied, with the variation being an increase when the load is a tensile load and a decrease when the load is a compressive load. 
     
     
         8 . A composite component according to  claim 3 , in which the variation in radial position is a decrease in displacement of at least a part of the second component from the axis when the load is varied, with the variation being a decrease when the load is a tensile load and an increase when the load is a compressive load. 
     
     
         9 . A structure comprising two or more composite components each of said components having a negative effective Poisson's ratio, each composite component comprising a first component and a second component extending longitudinally relative to an axis, the first component being provided around the second component through one or more turns, the one or more turns being spaced longitudinally relative to the axis, wherein a variation in the tensile or compressive load on the first component causes a variation in radial position of the second component relative to the axis. 
     
     
         10 . A structure according to  claim 9 , comprising at least a pair of composite components, said composite components being arranged adjacent to one another or in contact with one another. 
     
     
         11 . A structure according to  claim 9 , wherein the structure is formed from repeats of a unit comprising multiple composite components. 
     
     
         12 . A structure according to  claim 9 , wherein each composite component is adjacent to or in contact with two or more other composite components, so as to form a planar or sheet type structure. 
     
     
         13 . A structure according to  claim 9 , wherein each composite component is adjacent to or in contact with four or more other composite components. 
     
     
         14 . A structure according to  claim 10 , wherein the first components of the adjacent composite components are wrapped around the second component in opposite directions to one another. 
     
     
         15 . A structure according to  claim 9 , comprising one or more core components. 
     
     
         16 . A structure according to  claim 15 , in which the core component is a fibre wherein said fibre is solid or hollow. 
     
     
         17 . A structure according to  claim 15 , comprising three components provided to allow limited movement or no movement of the components over each other. 
     
     
         18 . A structure according to  claim 9 , comprising one or more matrix components. 
     
     
         19 . A structure according to  claim 18 , in which the matrix component resists the movement of the second component caused by load variation and/or encourages the return of the second component to the radial position it occupied prior to load variation. 
     
     
         20 . A structure according to  claim 9 , which has energy absorbing, impact absorbing and/or acoustic absorbing characteristics. 
     
     
         21 . A method for producing a composite component having a negative effective Poisson's ratio, the method comprising the steps of:
 forming a first component;   forming a second component; and   applying, the first component around the second component through one or more turns, the one or more turns of the first component being spaced longitudinally along the second component.   
     
     
         22 . A method according to  claim 21 , in which the modulus of elasticity of the first component is greater than the modulus of elasticity of the second component. 
     
     
         23 . A method according to  claim 21 , wherein the first component is applied around the second component in a helical manner, the tensile or compressive load on the first component is varied causing variation in the diameter of the helix of the first component, the variation in the diameter of the helix of the first component causing the second component to take on the form of a helix and/or causing variation in the diameter of the helix of the second component, wherein the diameter of the second component helix increases as the first component helix decreases in diameter, and the diameter of the second component helix decreases as the first component helix increases in diameter. 
     
     
         24 . A method according to  claim 21 , wherein the applying is provided by wrapping, spinning or covering.