Sonic impedance testing detects voids and unbonded regions as small as 1 inch in diameter by 0.03 inch thick. Measurements are made manually or by automatic scanning and the readout is made by meter or recorder

Haralson, H. S.

Haynes, J. L.

English

NASA Technical Reports Server

August 1970	 Brief 70-10012 
NASA TECH BRIEF 
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 Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Sonic Impedance Technique Detects Flaws in Polyurethane

Foam Spray-On Insulation 
Many techniques of nondestructive testing have 
been applied with limitedsuccess to the problem of 
detecting voids and unbonded areas within a poly-
urethane foam insulation layer. Techniques using 
microwave, X-ray, or neutron radiography; ultrasonic 
pulse echoes; electrostatic field intensity; low-fre-
quency sound velocity; sonic-brush noise generation 
and microphone pickup; and optical absorptance/re-
flectance have been rejected because of lack of 
sensitivity or high cost. 
The sonic impedance technique, on the other hand, 
has been found capable of detecting voids and Un-
bonded regions as small as 1 inch in diameter by 0.03 
inch thick. In addition, the technique has the following 
advantages: 1) the measurements can be made either 
manually or by automatic scanning; 2) the readout 
may be made directly by meter or recorder, providing 
more precise measurement than systems that require 
subjective judgement on the part of the operator; and 
3) the technique may be used even after the application 
of a protective coating over the insulation layer.
Note: 
The following documentation may be obtained 
from:
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.65) 
Reference: NASA-TM-X-53852 (N69-35245) 
Development of Nondestructive Test Device 
for Evaluation of 3/4-Inch Thick Poly-
urethane Spray-On Foam Insulation (SOFI) 
on the Saturn S-Il Stage. 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code GP, 
Washington, D.C. 20546. 
Source: J.L. Haynes and H.S. Haralson of

SPACO, Incorporated 
under contract to

Marshall Space Flight Center

(MFS-20561) 
Category 06 
Am 
MW
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=19700000012 2020-03-17T00:01:11+00:00Z


Sonic impedance technique detects flaws in polyurethane foam spray-on insulation

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