High performance sleeved interference fasteners for composite applications

Abstract

A fastener adapted to pass through aligned holes through workpieces is disclosed. The fastener includes a pin member having a transition portion wherein the diameter of the transition portion decreases radially as it extends from the smooth cylindrical shank portion to the threaded portion. The fastener may also comprise a sleeve member and a clamping means. The clamping means includes a collar, a nut, or any other possible clamping means. In exemplary embodiments, the workpieces can be formed with a plurality of materials, the materials including composite, metallic, or composite/metallic structures, any combination thereof. In particular embodiments, the fastener has interference capability of 0.0005 to 0.0100 inches in composite structures without risk of composite delamination or damage. As a result of the fastener interference, gaps between the fastener and the structure are eliminated thereby providing good electrical conductivity between components. As a result, the potential for electrical sparks is reduced, providing a safer fastener for use with aerospace applications.

What is claimed is: 
     
         1 . A fastener, comprising:
 a sleeve member having an enlarged head at one end and a tubular portion, the tubular portion having an inner surface with an inner diameter, and an outer surface with an outer diameter, wherein the outer diameter of the tubular portion is less than an inner diameter of inner surfaces of aligned holes of a plurality of workpieces in which the fastener is adapted to be installed, wherein the inner surface of the tubular portion of the sleeve member is coated with a low friction coating;   and a pin member having an enlarged pin head at one end thereof, a threaded portion at an opposite end thereof, a smooth cylindrical shank portion located below the pin head and having a diameter greater than the inner diameter of the tubular portion of the sleeve member, and a transition portion between the smooth cylindrical shank portion and the threaded portion,   wherein the pin member is adapted to be installed within the sleeve member, and   wherein the coating of the sleeve member is adapted to reduce the amount of friction as the smooth cylindrical shank portion of the pin member enters the sleeve member, and the transition portion reducing a radius between the smooth cylindrical shank portion and the threaded portion of the pin member for minimizing an installation force required for installing the pin member into the sleeve member, and   wherein a coefficient of friction between the inner surface of the tubular portion of the sleeve member and the smooth cylindrical shank portion of the pin member is less than a coefficient of friction between the outer surface of the tubular portion of the sleeve member and the inner surfaces of the aligned holes of the plurality of workpieces to expand the sleeve member into an interference fit with the plurality of workpieces in a range of about 0.0005 inch to about 0.0100 inch.   
     
     
         2 . The sleeve interference fastener of  claim 1 , wherein the transition portion includes an angle less than about 20 degrees from the smooth cylindrical shank portion as the diameter decreases radially from the smooth cylindrical shank portion to the threaded portion of the pin member. 
     
     
         3 . The fastener of  claim 1 , wherein the transition portion includes a length between 0.010 inch and 0.0290 inch, and the diameter of the transition portion decreasing radially between 0.004 inch and 0.005 inch as it extends from the smooth cylindrical shank portion to the threaded portion of the pin member. 
     
     
         4 . The fastener of  claim 1 , further comprising clamping means adapted to fit over the threaded portion of the pin member. 
     
     
         5 . The fastener of  claim 4 , wherein the clamping means includes a threaded nut member. 
     
     
         6 . The fastener of  claim 4 , wherein the clamping means includes a collar. 
     
     
         7 . The fastener of  claim 4 , wherein the clamping means includes a counterbore portion having a diameter greater than the outer diameter of the sleeve member.