Z-2 Threaded Insert Design and Testing

Date

2016-07-10

Journal Title

Journal ISSN

Volume Title

Publisher

46th International Conference on Environmental Systems

Abstract

NASA’s Z-2 prototype space suit contains several components fabricated from an advanced hybrid composite laminate consisting of IM10 carbon fiber and fiber glass. One requirement was to have removable, replaceable helicoil inserts to which other suit components would be fastened. An approach utilizing bonded in inserts with helicoils inside of them was implemented. The design of the interface flanges of the composites allowed some of the inserts to be a “T” style insert that was installed through the entire thickness of the laminate. The flange portion of the insert provides a mechanical lock as a redundancy to the adhesive aiding in the pullout load that the insert can withstand. In some locations it was not possible to utilize at “T” style insert and a blind insert was used instead. These inserts rely completely on the bond strength of the adhesive to resist pullout. It was determined during the design of the suit that the inserts did not need to withstand loads induced from pressure cycling but instead tension induced from torquing the screws to bolt on hardware which creates a much higher stress on them. Bolt tension is determined by dividing the torque on the screw by a k value multiplied by the thread diameter of the bolt. The k value is a factor that accounts for friction in the system. A common value used for k for a non-lubricated screw is 0.2. The k value can go down by as much as 0.1 if the screw is lubricated which means for the same torque, a much larger tension could be placed on the bolt and insert. This paper summarizes testing that was performed to determine a k value for helicoil inserts in the Z2 suit and how the insert design was modified to resist a higher pull out tension.

Description

United States
ILC Dover
NASA JSC
400
ICES400: Extravehicular Activity: Space Suits
Vienna, Austria
Amy Ross, NASA Johnson Space Center, USA
Richard Rhodes, NASA Johnson Space Center, USA
Robert J. Jones, ILC Dover, USA
David Graziosi, ILC Dover, USA
Jinny Ferl, ILC Dover, USA
Mitch Sweeney, ILC Dover, USA
Stephen Scarborough, ILC Dover, USA
The 46th International Conference on Environmental Systems was held in Vienna, Austria, USA on 10 July 2016 through 14 July 2016.

Keywords

space suit, threaded, inserts, k value, testing

Citation