View
7
Download
0
Category
Preview:
Citation preview
Piezoelectric sensors would significantly reduce the cost of damage detection
MAIN ACHIEVEMENT:
Piezoelectric sensors produce Lamb waves that can be used to identify damages at a lower cost in the increasingly common carbon fiber composites.
RE
SE
AR
CH
IM
PA
CT
STA
TU
S Q
UO
E
XP
ER
IM
EN
T
Damage Detection in Carbon Fiber Composite Materials Using Lamb Waves: FFT vs. PCA
Sensor 1 Sensor 2
Hole
Joshua Hardisty Dr. Arda Vanli Spandan Sharma High Performance Materials Institute – Florida State University
0
5
10
15
20
25
30
35
40
45
50
0.00 0.10 0.20 0.30 0.40 0.50 0.60
Pe
rce
nt
Dif
fere
nce
Hole size
PCA Damage Index vs. Damage Severity
6 in 10 in
FFT Chang (2011) Lecture Notes
• 10 x 27 in. carbon fiber composite plate
• Damages were introduced at varying distances (3 in. – 21 in.) and with different severity (1/8 in. – ½ in. hole)
• Lamb waves were sent through the plate by two sensors located at the ends of the plate
Signal and its Fast Fourier Transform due to a 13/32” hole at 3” away from Sensor 1
Fast Fourier Transform (FFT) Method
• The time domain signal is converted to a frequency domain signal • The frequency domain signal can be integrated to find the energy of the signal
Fast Fourier Transform (FFT) vs. Principle Component Analysis (PCA) • A comparison of the slopes of the FFT and PCA methods of analysis show that for every increase in damage size, there is a much larger drop in factor score/area • The PCA is much more sensitive
Principal Component Analysis (PCA) Method
• PCA is a method used to reduce the number of dimensions in an experiment • Principal components are found by projecting the data onto the principal axes of the covariance matrix
y = -7.9234x + 8.4317
0
1
2
3
4
5
6
7
8
9
0 0.2 0.4 0.6
Are
a
3 inch
6 inch
10 inch
14 inch
18 inch
21 inch
Area FFT Score vs. Damage distance
y = -36.449x + 16.068
-15
-10
-5
0
5
10
15
20
0 0.2 0.4 0.6
F
a
c
t
o
r
S
c
o
r
e
Damage size (inch)
3 inch
6 inch
10 inch
14 inch
18 inch
21 inch
Factor Score PCA vs. Damage distance
Ec
on
om
ic
V
alu
e
• Structural Health Monitoring in the aerospace industry is worth over $9 billion. • Piezoelectric sensors in combination with the PCA method could reduce the cost of damage detection by 50%.
To be able to accurately detect damages.
•Build a model to characterize the location and severity of damages in carbon fiber composites
EN
D-O
F-P
HA
SE
G
OA
L
Example: What is the distance of a 13/32 in. damage from sensor 1 with a DI percentage difference of 45%? Solve for x using the equation from the PCA DI vs. Distance graph with y = 45%: The answer should be about 5 in.
Carbon Fiber Composite Board
Piezoelectric Sensor
y = 0.01x4 - 0.72x3 + 14.99x2 - 131.56x + 418.71
R² = 1.00
0
20
40
60
80
100
0 5 10 15 20 25
Pe
rce
nt
Dif
fere
nce
Distance from Sensor
PCA Damage Index vs. Distance
13/32 in
y = 219.19x2 - 65.65x + 16.18 R² = 0.99
0
10
20
30
40
50
0.00 0.20 0.40 0.60
Pe
rce
nt
Dif
fere
nce
Hole size
PCA Damage Index vs. Damage Severity
6 in
Poly. (6 in)
Sensors on airplane wing
Future Inquiries with Principle Component Analysis (PCA) • “Tail” of the PCA vs. Distance graph increases when a decrease is expected • How sensitive is the measurement (How small are the damages this method can detect)?
8.1 8.3 7.8 8 9.3
9.6 9.9 8.7 8.7
9.9
0
5
10
15
20
25
2008 2009 2010 2011 2016
USD
Bill
ion
s
Year
Aviation Week "10-year Forecast" April 2011 – Market Value
Heavy Maintenance and Modifications
Line Maintenance
Airbus 30%
Boeing 61%
Other 9%
Fleet Distribution By Manufacturer - 2009
Ma
rke
t V
alu
e
How does Principal Component Analysis add value? • Fewer sensors result in lower fixed and installation costs
Why use piezoelectric sensors? • By using smarter sensor systems, maintenance time can be cut by over 40% • Most maintenance costs come from aircraft “down time” • Cutting maintenance time costs directly cuts total costs
Possible Manufacturers
International Air Transport Association
Recommended