Self-aligning plain spherical and plain cylindical oscillating bearings with self-lubricating elements are composed of 50 weight-percent chopped graphite fibers and 50 weight-percent polyimide

Jacobson, T. P.

Sliney, H. E.

English

NASA Technical Reports Server

Ottober 1975	 B75-10151 
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Lewis Research Center 
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Graphite Fiber-Polyimide Composite Rod End 
Bearings for High-Temperature High-Load Applications 
The Problem: 
Plain spherical bearings (also known as rod end 
bearings) are used in applications involving oscillating 
motion and requiring self-alignment. Aerospace applica-
tions include airframe bearings and bearings for engine 
control linkages. Airframe control surface bearings are a 
particularly difficult application because of the require-
ment for exceptionally high dynamic load capacity. 
Aerodynamic heating in supersonic flight, especially at 
speeds of Mach 3 or higher, will heat control surface 
bearings above the 436 K (325°F) service limit for the 
reinforced polytetrafluoroethylene (PTFE)-lined bearings 
currently used in many aircraft. PTFE bearings also are 
subject to cold flow under a combination of high loads 
and vibration. 
The Solution: 
Self-aligning plain spherical and plain cylindrical 
oscillating bearings with molded graphite-fiber-polyimide 
self-lubricating elements composed of 50 weight-percent 
chopped graphite fibers and 50 weight-percent polyimide. 
How It's Done: 
The resin used in the composite bearing material is an 
addition-type polyimide. Addition polymers form void-
free solids because they do not release gaseous reaction 
products during the final stages of polymerization. The 
graphite is in the form of chopped fibers. The composite 
has a yield strength of about 200 MN/m 2
 (30,000 psi) and 
an elastic modulus of 4.4 GN/m 2 (640,000 psi). The outer 
races and the journal are made of 440-C-HT steel, which 
has a hot hardness of Rockwell C-57 at 617 K (650°F) 
and has good oxidation resistance in air to about 811 K 
(1000°F). 
Dynamic load capacities and friction coefficients were 
determined for the three bearing designs shown in the 
figure. The composite was evaluated as a ball material and 
as a thin-wall bearing liner material. Dynamic load 
capacity tests consisted of step-wise increases in radial 
load at about 2200 N (500 lb) increments until bearing 
structural failure or a large and disproportionate increase 
in wear rate occurred. Oscillation frequency was 1 hertz at
±150 amplitude. Temperatures were: nominal room 
temperature (no external heat addition), 589 K (6000F), 
and 617 K(650°F).
OUTER RACE 
COMPOSITE 
SPHERICAL ELEMENT 
flcrii i STINt. .iflhiPNAi 
(A) DESIGN 1; MOLDED COMPOSITE BALL, JOURNAL OSCILLATES IN BEARING BORE. 
	
Snap ring -
	
,- Outer race 
	
I	 /
omposite 
Steel liner 
(b) Design 2; molded composite ball with steel-
reinforced bore. Ball oscillates in outer race. 
INRUST COLLAR 
(continued overleaf) 
This document was prepared under the sponsorship of the Natonai
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration Nether the United States
	 information corita,ned in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be tree from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19750000151 2020-03-19T20:22:14+00:00Z
Steel adaptor to fit bore 
in design 2 
Composite 
bushing - 
(C) Design 3; composite bushing and adaptor to allow 
testing to high unit loads. Journal oscillates in bore 
of bushing. 
The principal results were as follows: 
(I) Cylindrical steel bearings with thin-wall composite 
liners had dynamic load capacities of 280 MN/m' (40,000 
psi) at nominal room temperature and 240 MN/M2 
(35,000 psi) at 589 K (600°F). Friction was reduced by 
about 30 percent, typically to 0. 15, at the cost of a small 
reduction in load capacity by the addition of 10 weight-
percent graphite fluoride (CF) to the composite formu-
lation.
(2) Bearings with spherical elements made of the 
composite had a load capacity of about 67 MN/m2 
(10,000 psi) at room temperature and 25 MN/M 2 (3600 
psi) at 617 K (6500F). 
(3) The results demonstrated that oscillating bearings 
employing thin-wall graphite-fiber-polyimide liners should 
be useful in high load, low speed applications at 
temperatures to at least 589 K (600 0 F). For light-to-
moderate load applications, the molded composite may be 
used as the ball material in plain spherical bearings.
Notes: 
1. Further information is available in the following 
report: 
NASA TN-D-7880 (N75-15052), Dynamic Load 
Capacities of Graphite-Fiber-Polyimide Composites 
in Oscillating Plain Bearings to 340°C (650°F) 
Copies may be obtained at cost from: 
Aerospace Research Applications Center 
Indiana University 
400 East Seventh Street 
Bloomington, Indiana 47401 
Telephone: 812-337-7833 
Reference: B75-10151 
2. Specific technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B75-10151 
Patent Status: 
NASA has decided not to apply for a patent. 
Source: H.E. Sliney and T.P. Jacobson 
Lewis Research Center 
(LEW-12514)
is 
is 
. 
B75-101 51	 Category 06


Graphite fiber-polyimide composite rod end bearings for high-temperature high-load applications

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