Inert, strain sensitive tracer, cuprous oxide, added to polymeric adhesive ensures sufficiently large signal to noise ratio in NQR system output. Method is successful, provided that RF-transparent structural materials are used between modified adhesive and probe of NQR spectrometer

Hewitt, R. R.

English

NASA Technical Reports Server

July 1971	 Brief 71-10208 
NASA TECH BRIEF 
Marshall Space Flight Center	
_4V 
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. 
Nondestructive Testing of Adhesive Bonds by Nuclear Quadrupole
Resonance Method 
An investigation was conducted to determine the 
feasibility of using the nuclear quadrupole resonance 
(NQR) method for the nondestructive testing of ad-
hesive bonds. Tests were performed with three dif-
ferent polymeric adhesives obtained from commercial 
sources. 
Initial tests on the basic adhesive materials showed 
that they were incapable of providing an adequate 
NQR response. Therefore, an inert, strain-sensitive 
tracer, in the form of cuprous oxide (approximately 
1 to 3% by volume), was added to each of the ad-
hesives in order to ensure a sufficiently large signal-
to-noise ratio in the NQR system output. Several types 
of specimens were made with each of the three modi-
fied adhesives. The specimens included laminates of 
glass-fiber reinforced plastic panels, aluminum panels, 
combinations of these, and plastic and aluminum 
honeycombs bonded to the panels with the cuprous-
oxide modified adhesives. 
The results of the investigation showed that the 
NQR method can be used successfully for the nonde-
structive testing of the adhesive bonds, provided that 
rf-transparent structural materials are used between 
the modified adhesive and the probe of the NQR spec-
trometer. In general, it was not possible to determine 
the characteristics of the adhesive bonds in specimens 
incorporating aluminum structures, as the aluminum is 
opaque to the rf excitation energy. 
Notes: 
I. If adhesive bonds in aluminum laminates or honey-
comb structures are to be tested by this method, 
an external probe must be developed in order to 
bypass the rf energy from the aluminum and permit
detection of the NQR tracer responses in the ad-
hesive bonds. 
2. The milliwatt energy of the rf waves used in the 
NQR method has no adverse effect on the plastic 
structures, their nonmetallic reinforcing com-
ponents, or the adhesive materials. 
3. Any tracer added to the adhesive must be inert to 
the polymer, have a known NQR response, and be 
sufficiently strain-sensitive to provide a high signal-
to-noise NQR response when the test specimens are 
subjected to loading (tensile, compressive, etc). 
4. Specific technical questions may be directed to: 
Technology Utilization Officer 
Code A&TS-TU 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
5. The following documentation may be obtained 
from: 
National Technical Information Service 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.95) 
Reference: 
NASA-CR-6 1988 (N69-29388), Nondestruc-
tive Testing of Adhesive Bonds by the Nuclear 
Quadrupole Resonance Method 
Patent status: 
No patent action is contemplated by NASA. 
Source: R. R. Hewitt of

ARA, Inc.
under contract to

Marshall Space Flight Center

(MFS-21 160)

Cateeorv 01.04 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19710000207 2020-03-17T02:19:22+00:00Z


Nondestructive testing of adhesive bonds by nuclear quadrupole resonance method

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