Flush mounting of a sensor on a surface is provided by first forming a recessed area on the surface. Next, an adhesive bonding mixture is introduced into the recessed area. The adhesive bonding mixture is chosen to provide thermal expansion matching with the surface surrounding the recessed area. A strip of high performance polymeric tape is provided, with the sensor attached to the underside thereof, and the tape is positioned over the recessed area so that it acts as a carrier of the sensor. A shim having flexibility so that it will conform to the surface surrounding the recessed area is placed over the tape, and a vacuum pad is placed over the shim. The area above the surface is then evacuated while holding the sensor flush with the surface during curing of the adhesive bonding mixture. After such curing, the pad, shim, and tape are removed from the sensor, electrical connections for the sensor are provided, after which the remaining space in the recessed area is filled with a polymeric foam

Moore, Thomas C., Sr.

English

NASA Technical Reports Server

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United States Patent [19] 
US005149387A 
[ 1 1 ]  Patent Number: 5,149,387 
Moore, Sr. r451 Date of Patent: SeD. 22. 1992 
[54] FLUSH MOUhTING OF THIN FILM 
SENSORS 
[75] Inventor: Thomas C. Moore, Sr., Poquoson, 
[73] A-signee: Administrator of the National 
Va. 
Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 699,288 
[22] Filed: May 6, 1991 
[51] Int. C l . 5  .............................................. B29C 65/48 
[52] U.S. C1. ...................................... 156/241; 29/856; 
156/285; 156/293; 264/272.15 
[58] Field of Search ................. 156/79, 285, 241, 293; 
29/854, 855, 856; 73/768, 775, 776, 802; 
264/46.6, 46.7, 511, 272.11, 272.13, 272.15; 
374/208 
1561 References Cited 
U.S. PATENT DOCUMENTS 
3,428,933 2/1969 Gerstenberger . 
3.554.834 1/1971 Bennett et al. ... 
4,329,779 5/1982 England .............................. 156/241 
4.330.790 5/1982 Burns ............ .. 29/856 
4,349.281 9/1982 Onksen et a]. 374/136 
4,554,036 1 1/1985 Newsom ............................. 156/285 
4,864.724 9/1989 Bergstrom ............................ 29/854 
OTHER PUBLICATIONS 
Gureev, “Method of Protecting Strain Gauges (Ex- 
change of Experience”. Ind. Lab (USA) vol. 43, No. 1 
(Jan. 1977) (Publ. Jul. 1977) 73-775. 
Primar), Examiner-Michael W. Ball 
Assistant Examiner-Steven D. Maki 
Attorney, Agent, or Firm-George F. Helfrich 
is71 ABSTRAm 
Flush mounting of a sensor on a surface is provided by 
first forming a recessed area on the surface. Next an 
adhesive bonding mixture is introduced into the re- 
cessed area. The adhesive bonding mixture is chosen to 
provide thermal expansion matching with the surface 
surrounding the recessed area. A strip of high perfor- 
mance polymeric tape is provided, with the sensor at- 
tached to the underside thereof, and the tape is posi- 
tioned over the recessed area so that it acts as a carrier 
of the sensor. A shim having a flexibility so that it will 
conform to the surface surrounding the recessed area is 
placed over the tape, and a vacuum pad is placed over 
the shim. The area above the surface is then evacuated 
while holding the sensor flush with the surface during 
curing of the adhesive bonding mixture. After such 
curing, the pad, shim, and tape are removed from the 
sensor, electrical connections for the sensor are pro- 
vided, after which the remaining space in the recessed 
area is filled with a polymeric foam. 
10 Claims, 1 Drawing Sheet 
13 
12 ‘ 
19 
https://ntrs.nasa.gov/search.jsp?R=19920023776 2020-03-24T07:18:29+00:00Z
U*S* Patent Sep. 22, 1992 5,149,387 
14 12 ' 
19 
FIG. 1 
14 13 16 14 
13 
FIG. 2 
5,149,387 
1 2 
E. Covering the shim with a vacuum pad to evacuate 
the area above the aerodynamic surface and hold the 
sensor flush with the aerodynamic surface during cur- 
ing of the adhesive bonding mixture: 
F. After curing of the adhesive bonding mixture, 
removing the vacuum .pad, shim, and high performance 
polymeric tape, then attaching leads from the sensor to 
terminal pins, followed by filling remaining space in the 
recessed area with a polymeric foam, e.g., liquid ure- 
10 thane foam, and applying adhesive bonding mixture 
over the cured foam and curing the same to seal the 
entire assembly. 
Significant advantages of the process of the present 
FLUSH MOUNTING OF THIN FILM SENSORS 
ORIGIN OF THE INVENTION 
The invention described herein was made by an em- 
ployee of the U.S. Government and may be manufac- 
tured and used by or for the Government for govern- 
mental purposes without the payment of any royalties 
thereon or therefor. 
BACKGROUND O F  THE INVENTION 
5 
1. Field of the Invention 
The present invention generally to a method invention are: (1) the need for accurate machining of a 
has been eliminated, In this 
regard, it should be noted that even with accurate ma- 
Of flush mounting a sensor, especially a thin 
On an aerodynamic surface where surface conformity is sensor, 15 recessed area for the 
chining, there is no guarantee of surface conformity 
using methods of the prior art to mount the sensor. ( 2 )  
essential. 
2. Description of the Related Art 
A number Of methods exist for the mounting Of sen- The employment ofan adhesive bonding mixture which 
sors on aerodynamic surfaces of aircraft, wind tunnel 2o provides thermal expansion matching that of the sur- 
models, and the like, where surface conformity is essen- rounding aerodynamic surface helps prevent failures in 
tial. Most of these methods require the accurate machin- the backng which would result in failure of the 
ing Of a recessed area to precisely accommodate the 
sensor, by application Of a fastening agent 
sensor, (3) The employment of a polymeric foam fills 
remaining space in the recessed area without producing 
such as epoxy cement to 
surface. Several disadvantages are presented by such an 
mined depth, uniformly on a curved surface, is a diffi- 
the precisely at the 25 any large thermally induced stresses on sensor leads. 
Although specially suitable for the flush mounting of 
has utility in the mounting of other sensors, e.g., probe 
approach. First, the machining of a to a predeter- 
cult and expensive process. Second, the fastening %en- 
t-e.g.9 epoxy cement-changes in volume upon set- 30 ature sensors, and strain gauges, among others. 
thin film sensors, the method of the present invention 
type aerodynamic flow sensors, resistance-type temper- 
ting, often resulting in a sensor installation that is not 
precisely at the surface. Third, unless the fastening 
agent-e.g., epoxy cement-is extended with an appro- 
priate filler to provide thermal expansion matching, 
Sensor can Occur a s  a Of thermal, 
from temperature excursions associated with fllght and 
wind tunnel testing. 
SUMMARY O F  THE INVENTION 
invention to Provide a Process for the flush mounting of 
a sensor, especially a thin film sensor, on an aerodY- 
namic surface, which process obviates the difficulties 
and disadvantages of the prior art. This object and its 
attending advantages and benefits are achieved by the 45 flush mounting of the thin film sensor. 
provision of a process which is the cooperative combi- 
nation of the following procedural steps: 
A. Forming a recessed area on an aerodynamic sur- 
face, e.g., a fiberglass glove which is attached to a wing Referring now to the drawings, FIG. 1 shows an 
for use in studying natural laminar flow; 50 aircraft wing 10 to which fiberglass glove 11 is attached 
B. Introducing an adhesive bonding mixture into the for use in studying laminar flow. A recessed area 12 in 
recessed area which provides thermal expansion match- glove 11 is formed, as by routing out, and terminal pins 
ing with the surrounding aerodynamic surface, the ad- 13 are installed therein. Adhesive bonding mixture 14 is 
hesive bonding mixture comprising advantageously chosen to provide thermal expansion matching with the 
thermosetting epoxy cement and amorphous fumed 55 surrounding aerodynamic surface 11, and advanta- 
silica, the amount of which will vary in accordance geously comprises thermosetting epoxy cement and 
with the coefficient of thermal expansion of the surface; amorphous fumed silica. About 100 parts by volume of 
C. Providing a strip of high performance polymeric GA-2 TM epoxy cement, which is available commer- 
tape, e.g., polyimide tape, with the sensor to be cially, and about 70 parts by volume of Cab-0-SilQ 
mounted attached to the underside thereof, the strip of 60 filler, which is also available commercially have been 
high performance polymeric tape being positioned over used with particular success when glove 11 is fiberglass. 
the recessed area so that the tape acts as a carrier for the A strip of high performance polymeric tape 15 is 
sensor; provided, to the underside of which is attached the 
D. Providing a shim, e.g., of stainless steel, having a sensor 16 which is to be mounted in recessed area 12. 
flexibility so that it will conform to the aerodynamic 65 The sensor 16 shown here is a thin film sensor. How- 
surface surrounding the recess, the shim being posi- ever, other sensors, such as probe-type aerodynamic 
tioned over the strip of high performance polymeric flow sensors, resistance-type temperature sensors, and 
tape; strain gauges may also be employed. High performance 
BRIEF DESCRIPTION O F  T H E  DRAWINGS 
For a more complete understanding of the present 
invention, including its primary object and attending 
35 benefits, reference should be made to the Description of 
the preferred Embodiments which f o ~ ~ o w s ~  This de- 
scription should be read together with the accompany- 
ing drawings, wherein: 
FIG. 1 is a schematic which illustrates the process of 
It is accordingfy the Primary object of the Present 40 the present invention as applied to the flush mounting of 
a thin film sensor on a glove which has been attached to 
an aerodynamic surface, e.g., the wing of an aircraft; 
and 
FIG. 2 . i ~  a schematic which illustrates the completed 
DESCRIPTION O F  T H E  PREFERRED 
EMBODIMENTS 
5,149,387 
3 4 
polymeric tape 15 is advantageously a polyimide tape recessed area so that the tape acts as a carrier for 
such as Kapton @ polyimide. which is available com- the sensor; 
mercially. High performance polymeric tape 15 is posi- providing a shim having a flexibility so that it will 
tioned over recessed area 12 so that it acts as a carrier conform to the surface surrounding the recessed 
for Sensor 16. Shim 17 is then placed Over high perfor- 5 area, the shim being positioned over and Covering 
mance polymeric tape 15. Shim 17, which is preferably the strip of high performance polymeric tape; 
of stainless steel, should have a flexibility so that it will 'Overing the shim with a vacuum pad* curing the 
adhesive bonding mixture and evacuating the area conform to the surface of glove 11 over which it is 
above the surface while holding the sensor flush positioned. with the surface during curing of the adhesive 
bonding mixture; Shim 17 is now covered with vacuum pad 18, and the 
ing the vacuum pad and shim, and peeling the high whereby sensor 16 is held flush with the surface of 
glove 11 while adhesive bonding mixture 14 is being performance polymeric tape away from the sensor; 
cured. 15 providing electrical connections for the sensor fol- 
After adhesive bonding mixture 14 is cured com- lowed by filling remaining space in the recess area 
pletely, vacuum pad 18 is removed, followed by shim with a polymeric foam, then applying the adhesive 
17, and high performance polymeric tape 15 is then bonding mixture over the polymeric foam and 
peeled away from sensor 16. Leads are then attached curing the polymeric foam. 
from sensor 16 to terminal pins 13, after which the re- 20 2. The process of claim 1, wherein the surface is an 
maining space is recessed area 12 is filled to within 0.010 aerodynamic surface. 
inches of the surface surrounding the recessed area with 3. The process of claim 2, wherein the aerodynamic 
polymeric foam 19, which is advantageously a liquid surface is a glove which is attached to a wing for use in 
urethane foam. Finally adhesive bonding mixture 14 is studying natural laminar flow. 
applied over polymeric foam 19 and cured to seal the 25 4. The Process of claim 3, wherein the glove is a 
entire installation. fiberglass glove. 
FIG, 2 shows the completed flush mounting of thin 5. The process of claim 4, wherein the adhesive bond- 
functions of adhesive bonding mixture 14 and polymeric 
foam 19 are seen, as is the communication between 
sensor 16 and terminal pins 13. 
10 
area above the surface Of glove l1 is evacuated, after curing of the adhesive bonding mixture, remov- 
film Sensor 16 in glo\ie 11 attached to wing 10. The ing mixture comprises epoxy cement and amorphous 
fumed 
6. The process of claim 5,  wherein components of the 
adhesive bonding mixture are present in amounts pro- 
viding about 100 parts by volume of thermosetting 
epoxy cement and about 70 parts by volume of amor- 
phous fumed silica. 
7. The process of claim 1, wherein the high perfor- 
mance polymeric tape is a polyimide tape, 
8. The process of claim 1, wherein the shim is a stain- 
less steel shim. 
9. The process of claim 1, wherein the polymeric 
10. The process of claim 1, wherein the sensor is a 
30 
What is claimed is: 
1. A process for the flush mounting of a sensor in a 
introducing an adhesive bonding mixture into the 
recessed area, the adhesive bonding mixture pro- 
viding thermal expansion matching with the sur- 
face surrounding the recessed area; 
with the sensor to be mounted attached to the un- 
derside thereof, the strip of high performance poly- 
recessed area of a surface. which process comprises: 35 
providing a strip of high performance polymeric tape 40 foam is a liquid urethane foam. 
thin film sensor. 
meric tape being positioned over and covering the * * * * *  
45 
50 
55 
65 


Flush mounting of thin film sensors

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