BASIC CONCEPT reflecting layer glass capillary wall CENTER LINE optically active layers polyimide.
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O pticalW ave G uide Sensor for Structure H ealth & D am ageA ssessm ent 18 June 02 D r.EverettE.C rism an Scientist SNHA A irForce R esearch Laboratory
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Transcript of BASIC CONCEPT reflecting layer glass capillary wall CENTER LINE optically active layers polyimide.
Optical Wave Guide Sensor for Structure Health & Damage Assessment
18 June 02
Dr. Everett E. Crisman
Scientist
SNHA
Air Force Research Laboratory
Contributors
Everett E. Crisman & John S. DerovEverett E. Crisman & John S. DerovAir Force Research LaboratoryAir Force Research LaboratoryHanscom AFB, MAHanscom AFB, MA
* Otto J. Gregory & William B. Euler* Otto J. Gregory & William B. EulerUniversity of Rhode Island University of Rhode Island Kingston, RI Kingston, RI
*Supported in part by: *Supported in part by: NSF, Earthquake Hazard Mitigation ProgramNSF, Earthquake Hazard Mitigation Program
BASIC CONCEPTBASIC CONCEPT
reflecting layer
glass capillary wall
CENTER LINE
optically active layers
polyimide
SINGLE LIGHT BEAM/WAVE-GUIDE INTERACTION EVENT
glass capillary wall
CENTER LINE
n0
n1-i
n nn n
1 0
1 0
2
Fresnel’s Law (reflection)
n n1 1 0 0sin sin Snell’s Law (refraction)
Y
y
0eIyI Absorption (
HeNe Laser
Focusing opticsSource Fiber
Detector Fiber
Ref. Beam Detector
Signal Beam Detector
Electronic RatioSignal
Reference
Four Point Bending Apparatus
DisplacementMonitor
Plot of ratio versusdisplacement (~ strain)
Optical Strain Sensor
X inputY input
neutral axisd=0.53R
5.69 cm
0.32 cm
Four Point Bending
tension
compression
2a=2.92cm
d
2
2 2aStrain as a function of
Bend radius as a function of strain: Rd
2
N0
L
R d R d R
1
2 2 2( / )cos ( / ) /
Number of ‘bounces’ as a function of bend radiusFor principal ray, N0:
GI
I 1
0
Gage Factor:
TU
BE
DE
FL
EC
TIO
N,
m
m)
vs Pin Translation0.5 mm ID)
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0.00 0.50 1.00 1.50 2.00 2.50 3.00
Plain Glass with Al
Polyimide coated w/o Al
From K. Thomas et al.
INNER PIN TRANSLATION (mm)
0.00
0.20
0.40
0.60
0.80
1.00
0 500 1000 1500 2000 2500 3000
Without Reflector
With Reflector
With ITO & AL
MICRO STRAIN
NO
RM
AL
IZE
D I
NT
EN
SIT
Y R
AT
IO
Intensity Ratio vs Strain(0.5mm ID, Polyimide Coated)
K. A. Thomas, E. E. Crisman, W. B. Euler and O. J. Gregory Proceedings: SPIE Smart Structures and Materials 2000: S. C. Liu, ed., SPIE Press, v3988, p429 (2000)
MICROSTRAIN
NO
RM
AL
IZE
D I
NT
EN
SIT
Y
Intensity Ratio vs Strain(with ITO layer)
0
0.2
0.4
0.6
0.8
1
0 500 1000 1500
ITO/Al on Polyimide Coated Glass
Linear (ITO/Al on Polyimide CoatedGlass)
From K. Thomas et al.
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0.000 0.002 0.004 0.006 0.008 0.010
MICROSTRAIN
NO
RM
AL
IZE
D R
ES
PO
NS
EAl onlyAl + 400u SiAl +104nm SiUncoated
0
0.2
0.4
0.6
0.8
1
1.2
0 0.002 0.004 0.006 0.008 0.01
MICROSTRAIN
NO
RM
AL
IZE
D R
ES
PO
NS
E
Al +104nm Si
Sensor Signal Strength (I/I0) Gage Factor Polyimide/Al 8.8x10-2 69.7
6.92Ex10-2 70.44.37x10-2 92.3
Polyimide coated only 4.14x10-4 109.6
Polyimide/Al/40nm Si Polyimide/Al/104nm Si
SUMMARY
• Large, adjustable gage factors; >100
• Reproducible to 8000 micro-strain
• Easily adaptable to optical fiber data systems
• Robust
• Chemically Stable
• Simple & cheap material and design
• *Capable of both active and passive strain measurements.*
• *TEMPERATURE INSENSITIVE*
