Axial tension and compression are transmitted between end fittings and fiberglass tube without depending on glass-to-metal bonding, conventional fasteners or combination of these things. Joint design significantly reduces both structural weight of strut and its cross-sectional area

Barber, J. R.

Eugene, K. T.

Johnson, H. E.

English

NASA Technical Reports Server

August 1973	
-	 B73-10258 
• 
NASA TECH BRIEF 
Lewis Research Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Improved Fiberglass-to-Metal Joint

Produces Lighter Stronger Fiberglass Strut 
A highly efficient joint has been devised for attaching 
metal end fittings to tubular fiberglass struts. Axial 
tension and compression loads are transmitted between 
the fiberglass tube and the end fittings without de-
pending on glass-to-metal bonding, conventional fasteners 
such as rivets, bolts, etc., or a combination of these con-
nections. Conventional joints are inefficient, add sub-
stantial weight, and detract significantly from the high-
strength potential of tubular fiberglass structures com-
pared to equivalent metal structures. 
Use of this new joint design significantly reduces 
both the structural weight of the. strut and its cross-
sectional area. Reduction in cross-sectional area also 
results in a reduction in axial heat conduction. This new 
design, developed for cryogenic tank support members, 
can be applied to any axial tubular fiberglass structure 
where a high strength-to-weight ratio and/or low axial 
heat conduction are desired. 
In this design (see figure), the end fittings are attached 
during fabrication of the tubular section in a single 
operation: The fittings are mounted on a salt mandrel.
Fiberglass filaments are continuously wound under 
tension around the mandrel and over the skirts of the 
fittings, and imbedded in a--conventional resin system 
making an integral structure. Metal compression caps 
are mechanically attached to the end fittings, and the 
entire assembly is cured. After being cured, the salt 
mandrel is dissolved and washed out. 
With this new design, axial tension loads are trans-
ferred between the end fittings by the fiberglass fila-
ments which bear on the internal spherical surfaces of 
the end fittings. The load path is direct in that the fibers 
in tension are continuous around the end fittings and 
load transfer does not depend on shear through the bond 
line between the glass and the metal. Similarly, axial 
compression loads are transferred by the fiberglass 
structure which bears on the internal surface of the 
metallic compression caps. This load path is also direct 
and does not depend on lap-shear load transfer. This new 
design shows high structural efficiency compared to 
conventional structural fasteners applied to fiberglass 
composites. 
Rod End
	 Compression 
Bearing,	 Cap 
.
Body 
Fiberglass	 Assembly 
Winding 
Fitting	 Nuts
(continued overleaf) 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19730000258 2020-03-17T07:14:12+00:00Z
Notes: 
1. The following documentaion may be obtained from: 
National Technical Information Service 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.95) 
Reference: NASA CR-72538 (N69-25232), Cry-
ogenic Tank Support Evaluation - Interim 
Report 
Technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B73-10258
Patent status: 
NASA has decided not to apply for a patent. 
Source: J. R. Barber 
Lewis Research Center and
H. E. Johnson and K. T. Eugene of 
Lockheed Missiles & Space Co. 
under contract to
Lewis Research Center
(LEW-1 1661)
. 
B73-10258
	 Category 08


Improved fiberglass-to-metal joint produces lighter stronger fiberglass strut

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