Integrated variable stiffness member

Abstract

An oblong stiffening member such as a sail batten having a tapered geometry formed by a pair of parallely spaced apart oblique circular cones interconnected by a webbing strip. The member can be made from a unitary piece of fiber composite material such as a carbon fiber infused polymer wherein the orientations of the fibers are varied to provide both bending and torsional strength and stiffness that varies along the length of the member. Such properties can be useful in sail battens due to the rigorous dynamical forces subjected to such structures.

What is claimed is: 
     
         1 . An improved variable stiffness structural member comprises:
 said member having an oblong shape in a longitudinal direction;   said member having a proximal end and a distal end;   a first zone between said proximal end and said distal end;   wherein said first zone comprises a first fiber reinforced material having a first set of plural fiber orientations;   wherein first fiber reinforced material has a first longitudinal stiffness and a first latitudinal stiffness different from said first longitudinal stiffness.   
     
     
         2 . The member of  claim 1 , wherein said member further comprises:
 a second zone between said proximal end and said distal end;   wherein said second zone comprises a second fiber reinforced material having a second set of plural fiber orientations different from said first set of plural fiber orientations;   wherein said second fiber reinforced material has a second longitudinal stiffness different from said first longitudinal stiffness.   
     
     
         3 . The member of  claim 2 , wherein said first set of plural fiber orientations comprises a first fiber layer orientation rotated a first non-zero angle with respect to a second fiber layer orientation. 
     
     
         4 . The member of  claim 3 , wherein said first set of plural fiber orientations further comprises a third fiber layer orientation rotated a second non-zero angle with respect to said second fiber layer orientation, and wherein said second non-zero angle is different from said first non-zero angle. 
     
     
         5 . The member of  claim 4 , wherein said second set of plural fiber orientations comprises a fourth fiber layer orientation rotated a third non-zero angle with respect to a second fiber layer orientation. 
     
     
         6 . The member of  claim 5 , wherein said first non-zero angle is at least 90 degrees, said second non-zero angle is at least 45 degrees, and said third non-zero angle is at least 30 degrees. 
     
     
         7 . The member of  claim 2 , wherein said first set of plural fiber orientations and said second set of plural fiber orientations have a least one fiber layer in common. 
     
     
         8 . The member of  claim 1 , wherein said member further comprises:
 a pair of substantially parallel, oblong, spaced-apart rods, laterally joined by a webbing strip; and,   wherein each of said pair of rods gradually tapers from said proximal end toward said distal end.   
     
     
         9 . The member of  claim 8 , wherein said first one of said pair of rods comprises an axial hollow. 
     
     
         10 . The member of  claim 9 , wherein said first one of said rods has a substantially conical shape; and wherein said axial hollow has a substantially conical shape. 
     
     
         11 . The member of  claim 1 , wherein said member has a variable cross-sectional geometry along a logitudinal length of said member. 
     
     
         12 . The member of  claim 1 , wherein said member further comprises:
 said member having a first cross-sectional area near said proximal end and a second cross-sectional area near said distal end;   wherein said first cross-sectional area is larger than said second cross-sectional area.   
     
     
         13 . The member of  claim 12 , wherein said first cross-sectional area is substantially barbell shaped. 
     
     
         14 . The member of  claim 12 , wherein said first cross-sectional area comprises a pair of spaced apart, interconnected, diametrically symmetric geometric shapes selected from the group consisting of:
 circles, ellipses, triangles, squares, rectangles, trapezoids, pentagons, hexagons, heptagons, octagons, nonagons, and decagons.   
     
     
         15 . The member of  claim 1 , wherein said member is formed by a unitary piece of composite material. 
     
     
         16 . The member of  claim 8 , wherein said rods have a substantially oblique circular conical shape. 
     
     
         17 . The member of  claim 8 , wherein both of said pair of rods are similarly shaped and dimensioned. 
     
     
         18 . The member of  claim 12 , wherein said first cross-sectional area has a width dimension corresponding to said webbing strip, and a height dimension corresponding to an outer diameter of said one of said rods, and wherein said width dimension is equal to or greater than said diameter dimension. 
     
     
         19 . The member of  claim 1 , wherein said member further comprises:
 said member having a first width dimension at said proximal end and a second width dimension at said distal end; and,   wherein said first width dimension is equal to or greater than said second width dimension.   
     
     
         20 . The combination of a sailing craft having a sail and a plurality of sail battens, wherein at least one of said battens comprises:
 a fiber reinforced composite structural member having a first set of plural fiber orientations;   wherein said member comprises:
 a pair of substantially parallel, spaced-apart tapering rods, laterally joined by a webbing strip. 
   
     
     
         21 . An improved variable stiffness structural member comprises a fiber reinforced material having plural fiber orientations selected to adjust a longitudinal stiffness different from a latitudinal stiffness.