Fasteners with conforming sleeves
View Patent ↗A sleeve interference fastener including a conformable sleeve, wherein the conformable sleeve is comprised of at least one first material having a hardness of X, and a pin member, wherein the pin member is comprised of at least one second material having a hardness of Y, wherein X is sufficiently less than Y so that, in an installed position of an interference fit, at least a portion of the at least one first material of the conformable sleeve conforms to a contour of an inner surface of a hole of a composite structure so as to create a continuous electrical contact at an interface between the inner surface of the hole of the composite structure and the conformable sleeve.
1. A sleeve interference fastener, comprising:
a conformable sleeve having a head at one end thereof and a tubular portion,
wherein the tubular portion is comprised of an inner base layer,
wherein the tubular portion has an inner diameter and an outer diameter, wherein
the outer diameter of the tubular portion is less than an inner diameter of a hole of a composite structure, and
wherein the inner base layer is comprised of at least one first material having a hardness of X and a malleability of S;
an outer coating layer,
wherein the outer coating layer is located on the outer diameter of the tubular portion of the conformable sleeve,
wherein the outer coating layer is comprised of at least one second material having a hardness of Y and a malleability of T, and
wherein the at least one second material is electrically conductive so that the outer coating layer is configured to dissipate a current from the conformable sleeve into the composite structure;
a pin member,
wherein the pin member has at least a pin head at one end, a locking portion at an opposite end of the pin head, and a shank portion therein between,
wherein the shank portion, located below the pin head, has a diameter greater than the inner diameter of the tubular portion of the conformable sleeve, and wherein
the pin member is comprised of at least one third material having a hardness of Z;
wherein, based on i) Y being equal to or less than 100 HRB on Rockwell B scale, ii) Y being less than X, iii) Z being equal to or higher than X, and iv) S being less than T, the conformable sleeve is configured so that at least a portion of the outer coating layer can fill voids being present within an inner surface of the hole of the composite structure to result in an interference fit formed between the conformable sleeve and the inner surface of the hole of the composite structure.
2. The sleeve interference fastener of claim 1 , wherein the outer coating layer is a fixed solid coating.
3. The sleeve interference fastener of claim 2 , wherein the fixed solid coating comprises: i) at least one organic material and ii) at least one conductive filler material.
4. The sleeve interference fastener of claim 2 , wherein the fixed solid coating comprises a metal material.
5. The sleeve interference fastener of claim 4 , wherein the metal material comprises one or more metal elements selected from a group consisting of silver, aluminum, gold, and nickel.
6. The sleeve interference fastener of claim 1 , wherein, to facilitate a movement of the pin member through the conformable sleeve, the fastener further comprises a lubricant.
7. The sleeve interference fastener of claim 6 , wherein the lubricant comprises a conductive solid film material.
8. The sleeve interference fastener of claim 7 , wherein the conductive solid film material comprises carbon nano-tubes at a concentration between 0.05 to 30 percent of a total weight of the conductive solid film material.
9. The sleeve interference fastener of claim 1 , wherein a thickness of the outer coating layer varies in a range of 3 to 25 microns.