1 Damage State Awareness in Composite Laminates Via Ultrasonic Guided Waves Cliff Lissenden Joseph...
-
Upload
guy-sylvester -
Category
Documents
-
view
223 -
download
1
Transcript of 1 Damage State Awareness in Composite Laminates Via Ultrasonic Guided Waves Cliff Lissenden Joseph...
1
Damage State Awareness in Composite Laminates Via Ultrasonic Guided Waves
Cliff LissendenJoseph Rose Engineering Science & MechanicsThe Pennsylvania State University
Workshop on Prognosis of Aircraft and Space Devices, Components, and Systems
Sponsored by AFOSR
Cincinnati, OH
19-20 February 2008
Impact delamination in cross-ply laminate
2
We focus on understanding guided wave prop-agation in order to improve penetration power and sensitivity to damage.
Analysis of guided waves in composite laminates
Mode excitation and tuning
Synthetic reconstruction
0 20 40 60 80 100-6
-4
-2
0
2
4
6x 10
-3
Time (s)
Am
plit
ud
e
Current issues and capabilities
3
Ray distributions for 16 and 8 element arrays
Methods for tomographic imaging of internal damage are available.
Enable reconstruction based on signal difference, group velocity, etc.
Array of PWAS Air-coupled transducer test bed
4
Tomographic imaging enables visualization of internal damage.
4.23 J Impact delamination in ([0/90]s)6 CFRP with a 178 mm diameter circular array of PWAS
C-scan 16 element array 8 element array
Needs: penetration distance, number of sensors, damage sensitivity, critical size
5
Material anisotropy results in skew angles for guided wave propagation that must be accounted for in monitoring.
Unidirectional CFRP with fibers oriented at 22.5°. Wave activation is in the 0° direction.
[0/45/90/-45]s CFRP laminate 200 mm x 200 mm x 1.6 mm excited by 3 cycle toneburst from 10 mm diameter PWAS
300 kHz (movie)
100 mm1
00 m
m
6
Focusing of energy from a phased array can sweep through a plate.
Beam control of a linear phased array for an aluminum plate, as pioneered by V. Giurgiutiu
7
Guided wave ultrasonics can monitor structures. To be used effectively, the underlying wave mechanics must be well understood.
Dispersion curves and wave structure are the foundation
Mode & frequency selection encompasses
many application specific aspects
Sensor design
DAQ & analysis
FrequencyGroup velocityDispersivityExcitabilityAttenuationDamage sensitivity
Signal processingDamage mechanicsEtc.Angle beam
CombNatural tuningPhased array tuning
Prognostics
8
Lamb-like and SH waves are not decoupled in anisotropic materials.
Phase velocity dispersion curves for guided waves propagating in the 0o direction of a [(0/45/90/-45)s]2 carbon/epoxy laminate.
Simply number modes sequentially
SAFE (lines) & GMM (symbols) compare well
9
Group velocity and attenuation dispersion curves provide valuable information for health monitoring.
Group velocity dispersion curves Attenuation dispersion curves for guided waves propagating in the 0o direction of a [(0/45/90/-45)s]2 carbon/epoxy laminate.
Kelvin-Voigt model1 neper = 8.69 dB
10
Multiple modes are often excited simultaneously.
5 cycle Hanning windowed tone burst excitation with 200 kHz central frequency – normal loading w/ 1 mm wide transducer.
Mode 1 dominates low frequency region
Natural tuning
0 0.5 1 1.5 20
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
Frequency (MHz)
Mo
de
exc
itab
ility
Mode 1Mode 2Mode 3Mode 4Mode 5Mode 6
0 0.5 1 1.5 20
0.5
1
1.5
2
2.5
3
3.5
4
Frequency (MHz)
Am
plit
ud
e1
Mode 1
Mode 3
11
Frequency (MHz)
Pha
se v
eloc
ity (
km/s
)
1 2 3 4 5
2
4
6
8
10
12
14
1
2
3
4
5
6
7
8
9
0 degree
The source influence can be shown clearly in phase velocity-frequency space.
10 mm transducer, 1 MHz central freq. 10 cycle excitation, variable incidence angle, 2 mm aluminum plate
Frequency (MHz)
Pha
se v
eloc
ity (
km/s
)
1 2 3 4 5
2
4
6
8
10
12
14
5
10
15
20
10 degree
Frequency (MHz)
Pha
se v
eloc
ity (
km/s
)
1 2 3 4 5
2
4
6
8
10
12
14
5
10
15
20
20 degree
Frequency (MHz)
Pha
se v
eloc
ity (
km/s
)
1 2 3 4 5
2
4
6
8
10
12
14
5
10
15
20
30 degree
Frequency (MHz)
Pha
se v
eloc
ity (
km/s
)
1 2 3 4 5
2
4
6
8
10
12
14
0
5
10
15
20
40 degree
Frequency (MHz)
Pha
se v
eloc
ity (
km/s
)
1 2 3 4 5
2
4
6
8
10
12
14
0
5
10
15
20
50 degree
Frequency (MHz)
Pha
se v
eloc
ity (
km/s
)
1 2 3 4 5
2
4
6
8
10
12
14
0
5
10
15
20
60 degree 1D model, F(x,t)
2D Fourier Transform, F(k,)
Source Influence spectrum, F(cp,f)
cp = /f, f = /2
12
The source influence is determined using the normal mode expansion (NME).
Modes are orthogonal; v*(H) = complex conjugate of normalized velocity at top surface, T = traction vector, P = Poynting vector, x1 = prop. dir., x3 = thickness dir.
Logo
13
*3
1
131131
3131
expexp4
expˆˆ,,
exp,,
2
1
xikdikTP
Hvxa
tixxxaxtxx
tixxatxx
n
L
L nnn
n
nn
n
nn
n
σσ
vv
Velocity field
Stress field
Transducer length
13
A linear phased array provides mode tuning by using time delays.
Elements uniformly spaced at distance d
time delays
Logo
pc
dt
Guided wave
Li & Rose, 2001, IEEE Trans. 48(3):761
d
14
Frequency tuning and time delays provide tremendous flexibility for mode tuning.
200 kHz central frequency 1 MHz central frequency
d = 2 mm
Mode 1, cp = 1.5 km/s, t = 1.33 s t = 1.09 s
Mode 3, cp = 6.6 km/s, t = 0.303 s t = 0.76 s
Frequency (MHz)
Ph
ase
ve
loci
ty (
km/s
)
0.5 1 1.5 2
2
4
6
8
10
12
14
16
18
20
0
10
20
30
40
50
60
70
Frequency (MHz)
Ph
ase
ve
loci
ty (
km/s
)
0.5 1 1.5 2
2
4
6
8
10
12
14
16
18
20
0
10
20
30
40
50
60
70
Frequency (MHz)
Ph
ase
ve
loci
ty (
km/s
)
0.5 1 1.5 2
2
4
6
8
10
12
14
16
18
20
0
2
4
6
8
10
12
14
Frequency (MHz)
Ph
ase
ve
loci
ty (
km/s
)
0.5 1 1.5 2
2
4
6
8
10
12
14
16
18
20
0
2
4
6
8
10
12
14
16
15 0 20 40 60 80 100-8
-6
-4
-2
0
2
4
6
8x 10
-3
Time (s)
Am
plit
ud
e
Time (s)
Ele
me
nts
0 20 40 60 80 100
1
2
3
4
5
6
7
8
9
10
Time (s)
Ele
me
nts
0 20 40 60 80 100
1
2
3
4
5
6
7
8
9
10
0 20 40 60 80 100-6
-4
-2
0
2
4
6x 10
-3
Time (s)
Am
plit
ud
e
Tuned mode 1 Tuned mode 3
Synthetic phased array tuning provides flexibility through reconstruction.
16
In summary, phased array transducers can be used for synthetic focusing in composite laminates.
Mode selection and tuning can improve sensitivity and penetration power
Long range guided wave monitoring capabilities
Questions? Logo