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Document Sample
Effect of Ply Cracks on Delamination
Growth
Jae Noh
John Whitcomb
Texas A&M University
Center for Mechanics of Composites
1
Flight Cycle of a Reusable Launch Vehicle
Re-entry
Tanks empty
T=400K
Flight
Full LH2 Landing
T=20K Tanks empty
T=300K
Pre-fueling
T=300K
(Ambient)
•Severe temperature extremes (from processing temperature down to near absolute zero)
can cause distributed damage in composite => leakage!
Reference: S.S. Kessler, T. Matuszeski and H. McManus. Proceedings of the American Society for Composites (ASC), 2001.
2
Damage Network
delamination
TMC
Simulation by CFD program, Fluent
3
Focal Areas
• Formation of damage
• The leakage path, which includes the opening of cracks, the
connectivity of the cracks, and the uncracked material
• The effective permeability for a given leakage path
• Evaluation of current and exploration of new nondestructive
evaluation techniques
Model to predict microcracking
induced permeability of
cryogenic composite tanks
4
Predict Microcracking Induced Experimental Damage Characterization
Permeability of Cryogenic
Composite Tanks Ultrasonic
Analysis of Damage
delamination X-ray
Simulation of Leakage Path
delamination
Crack opening volume
G, SERR 7
6
TMC 5
4
5.00E+06 3
4.50E+06
[0/0/0]
4.00E+06
2
[90/0/90]
3.50E+06
[45/0/45]
3.00E+06
1
2.50E+06
0
2.00E+06
1.50E+06
delamination 0 0.5 1
1.00E+06
5.00E+05 Load case 1 crack density
0.00E+00
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Load case 2
Load case 3
5
Whitcomb, Lagoudas, Kinra, Noh
Computational Modeling
Fracture mechanics prediction of damage formation and
growth
Pop-in of transverse matrix cracks
Delamination growth near non-intersecting and
intersecting matrix cracks
•Prediction of opening of damage
delamination
Transverse matrix cracks TMC
Opening displacements due to delamination at tips of
TMC
Single crack
Intersecting cracks
• Effective permeability of laminates with matrix cracks and
delaminations
Can laminate design (e.g. stacking sequence) reduce the
formation or the effect of damage? 6
Damage Configurations
0
90
0
0 0 0
90 90
0 0
7
Delamination at Intersection of TMCs
y
TMC
in 0o ply
0o ply
Delamination 90o ply
TMC in 90o ply
x 8
Virtual Crack Closure Technique (VCCT)
z
y
x 1
GI Fz z
z 2 dA
y 1
GII Fy y
x 2 dA
1
Delamination front GIII Fx x
2 dA
9
FEM Analysis without Contact Constraints
0o
90o
0o
90o
undeformed
deformed
10
GI, GII, and GIII for [90/0c/90c/0]s
G (J/m2)
<ex> = 0.5%
y 350
s
GIII
GII
x
GI S
without contact constraints
11
GI, GII, and GIII for [90/0c/90c/0]s s y
G (J/m2)
350 <ex> =
0.5% x
GIII <ex> =<ey> = 0.5%
GII G (J/m2)
700
S
GI GIII
G (J/m2) <ey> = 0.5%
350 GII
GIII
GII
S
S GI
GI 12
GI, GII, and GIII for [45/0c/45c/0]s
G (J/m2)
<ex> = 0.5%
300
y
GII
s
x
GIII
S
GI
G (J/m2) G (J/m2)
<ey> = 0.5%
<ex> =<ey> = 0.5%
300
1000
GIII
GII GII
500
GIII
S
S
GI GI 13
Variation of GIII with Delamination Size
s y
GIII (J/m2)
450
R=400 100
R=200
R=100 y x
R
x
-400 -200 -100 0 100 200 400
x
14
Variation of GII with Delamination Size
s y
y
100
GIII (J/m2)
100
x
Radius
R=100 x
50
R=200
R=400
-400 -200 -100 0 100 200 400
x
15
Variation of GII and GIII with Delamination Shape
(Circle vs. Ellipse)
GIII (J/m2)
s y
300
100
x
GIII
Ellipse y y
Circle
GII
x x
400 100
-10 0 10
X
16
Lack of Interaction Between TMCs
Delamination Radius = .5h
Two TMCs
G (J/m2) <ex> = 0.5%
350
Two TMCs GIII
One TMC One TMC
GII
GI S
17
Opening for Different Damage Configurations
( <ex> = 0.5% )
0 0 d 0 d
0
90 90 90
0 0 0
S S
Opening (mm)
6 Opening (mm) two delaminations
5
5
two delaminations
4
4 one delamination
3 cd=0.1
one delamination
3
cd=0.5 2
2 cd=0.1 4
2u y a2 x2 1 cd=0.5
E
1
0
0 0 0.5 1
0 100 200 300 400 500 600 700 800 900 1000
Normalized delamination length, d/s
Delamination length, d (mm) (s=crack spacing) 18
Opening of TMC + Delamination
d1
d2
delamination
TMC
19
Comparison of 2D and 3D Configuration
0 d s y
90
100
0
S x
cd = 0.05
3.
Opening 2.
(mm) <ex> = 0.5%
1.
0 100 200 300 400 500
delamination length, d or radius (mm) 20
Effect of Stacking Sequence on Opening
<ex> =<ey> = 0.5%, delamination radius = 200 mm
z
2.092
y
2.272
[90/0c/90c/0]
x
1.744
1.880 [45/0c/45c/0]
21
Summary
22
Summary
s y
x
s y
y
s
x
x 23
Computational Modeling
Prediction of damage formation and growth
Average strain energy release rate associated with pop-in of
transverse matrix cracks
Strain energy release rate for delamination growth near
non-intersecting and intersecting matrix cracks
•Prediction of opening of damage delamination
TMC
Transverse matrix cracks
Opening displacements due to delamination at tips of TMC
Single crack
Intersecting cracks
• Effective permeability of laminates with matrix cracks and
delaminations
Can laminate design (e.g. stacking sequence) reduce the
formation or the effect of damage? 24
0
0
0 0
90
90 90
0 0 0
25
Laminate with Matrix Cracks and Delaminations
Close-up of single intersection
Laminate with intersecting matrix cracks + Delaminations
Typical FEA model
*Various delamination shapes to be considered 26
Strain Energy Release Rate for Delamination
Growth Near Intersecting Matrix Cracks
z
Circle y
y
q
x
Ellipse y
x
q
x
27
FEM Analysis
z
y
x
x 28
Warning! Calculation of G
y
Crack line
Delta Area
x
Crack line
x 29
