Nondestructive Evaluation of Cryogenic Composites for Prediction of Permeability

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Non-destructive Evaluation of Cryogenic
Composites for Prediction of Permeability
Vikram K. Kinra Atul S. Ganpatye Konstantin
Maslov Center for Mechanics of
Composites Department of Aerospace
Engineering Texas AM University
Sponsor UNO Research and Technology Foundation
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Motivation for this work

• X-33 LH2 tank leakage

• Permeability of LH2 in cryogenic composite tanks
  is directly related to the connectivity between
  cracks in different plies of the composite
• To establish the path of leakage it is important
  to quantify and locate damage in EACH ply.
  Ply-by-ply damage evaluation is critical

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Rate of leakage is different in different areas
of a laminate
Leakage of air through the 8-ply 0/45/90/-45s
George C. Marshall Space Center specimen (
Scotty Sparks Specimen)
Moderate leakage
Slow leakage
100 µm
Fast leakage
Air bubble escaping through other route
Videos suggest that the damage state is different
at different locations on the specimen
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Ultrasonics
Polar Backscattering for Ply-by-Ply Damage
Evaluation
Orientation of the ultrasonic transducer with
respect to the cracked ply
x
x
a Angle of Incidence 25o
ß Azimuthal angle
How does it work ?
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Ply-by-Ply Damage Evaluation
Ultrasonic images of 1st and the 2nd plies of
the 8-ply, 0/45/90/-45s George C. Marshall
Space Center composite laminate
20o Angle of Incidence 20 MHz transducer (
White lines are cracks)
A schematic of the optically detected cracks in
the 1st ply is shown with blue lines below the
ultrasonic image
Short cracks
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Ply-by-Ply Damage Evaluation
Ultrasonic images of the 3rd , 4th and 5th plies
Short cracks
A schematic of the optically detected cracks in
the 4th ply is shown with blue lines along the
left side of the ultrasonic image
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Ply-by-Ply Damage Evaluation
Ultrasonic images of the 6th , 7th and 8th plies
Short cracks
Short cracks
A schematic of the optically detected cracks in
the 8th ply is shown with blue lines below the
ultrasonic image
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Summary ALL the 8 plies
0/45/90/-45s George C. Marshall Space Center
composite laminate
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Ply-by-Ply Damage Evaluation
Ultrasonic images of all the plies of the 8-ply,
0/45/90/-45s B-08-20-CL laminate
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Ply-by-Ply Damage Evaluation
Ultrasonic images of all the plies of the 8-ply,
0/45/90/-45s , B-03-20-CL laminate
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Presence of short cracks in constraint plies
X-ray
0.25
Short cracks in the 2rd and the 7th ply 45 of
the 8-ply 0/45/90/-45s , B-03-20-CL
laminate These cracks are critical in
permeability studies
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Presence of short cracks in constraint plies
Ultrasonics
Short cracks in the 2nd ply 45 of the 8-ply
0/45/90/-45s George C. Marshall Space Center
composite laminate
The short cracks are aligned along the direction
of the fully developed cracks in the adjacent ply
A schematic of the optically detected cracks in
the 1st ply is shown with blue lines below the
ultrasonic image
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Presence of short cracks in constraint plies
X-ray
After sectioning
Before sectioning
0.25
Short cracks in the 2nd ply 45 of the 8-ply
0/45/90/-45s , B-08-20-CL laminate
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Processing ultrasonic data for feeding into a
permeability model or a stress analysis model
(0,0)
Points of Intersection between cracks in two
adjacent plies
8-ply 0/45/90/-45s GMSC composite laminate
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Concurrent thermo-mechanical loading and
ultrasonic NDE
Pure bending at cryogenic temperature
Cylindrical Bending Test Fixture for
thermo-mechanical loading Max strain 3.9 x 10-3
Loading paths for the 32-ply 45,0,-45,90s4
IM7/8552 laminate
Load
Specimen
Cracks
Bending at room temperature - No cracks observed
Cooling to 77K no bending - No cracks
observed
Bending at LN2 temperature - Cracks observed
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Concurrent thermo-mechanical loading and
ultrasonic NDE
Pure bending at cryogenic temperature
2a Contact length 2L Length of specimen F
Applied Force
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Concurrent thermo-mechanical loading and
ultrasonic NDE
Pure bending at cryogenic temperature
32-ply 45,0,-45,90s4 IM7/8552 laminate
subjected to cylindrical bending at LN2
temperature
Ultrasonic image of cracks in the 4th and the 5th
plies 90o after pure bending at LN2 temperature
Blue lines on both sides represent a schematic of
optically detected cracks
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Collaboration with University of New Orleans
Paul Schilling and Melody Verges
0/90s 5 mm x 50 mm ( 0.2 x 2 )
specimen Cracks in the 902 ply-group

• TAMU Polar Backscattering
• Schematic of the X-ray image
• UNO Scaled X-ray image

(b)
(c)
(a)
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Polar backscattering image of 0/90s
Panel5-IV-(II)-2-90
Detection of cracks through a rough surface
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Conclusions
A technique for the ply-by-ply detection of
matrix cracks has been successfully developed and
implemented The technique is being extended to
the detection of short cracks in cryogenic
composite laminates