Christoffersen, Roy

McDaniels, Steve

Rahman, Zia

Wright, M. Clara

NASA Technical Reports Server

Kennedy Space Center
Engineering and Technology
-l
Utilize
Ch
Materials Failure
Microscopy & Microanalysis 2011
August 10, 2011
https://ntrs.nasa.gov/search.jsp?R=20110014562 2019-08-30T16:47:54+00:00Z
Kennedy Space Center
Engineering and Technology Research Collaboration
2
• Kennedy Space Center (KSC)
- Materials Science Division: Clara Wright, Steve McDanels
~ Metallography, SEM, XRD, logistics
• Johnson Space Center (JSC)
- Astronaut Office: Col. Pam Melroy, Dr. Danny Olivas
~ Survivability study
Materials & Processes (M&P) group
~ Metallography, SEM
-- Astromaterials Research & Exploration Science (ARES) Lab: Dr. Roy Christoffersen
~ TEM
• Langley Research Center (LaRC)
- M&P group
~ TEM (SAD indexing)
• University of Central Florida (UCF)
- Materials Characterization Facility (MCF): Zia Rahman*
~ In-Situ FIB Sample Prep, TEM - -
* Now at ARES lab at JSC
Kennedy Space Center
Engineering and Technology Columbia Accident
<
...._-----
•
3
"elnforcecl CertK>n.certK>n Penels
(1.10 end 1••17)
• The breakup occurred on February 1, 2003
- Velocity was in excess of Mach 18 (13,700 mph)
- Altitude was over 60,960 m (200,000 ft)
Resultant debris experienced temperatures in
excess of 17500 G (3182°F).
• The Columbia Accident Investigation Soard (GAlS)
determined that foam debris impact from the external
tank left bipod ramp breached the left hand wing
leading edge reinforced carbon-carbon (RGG) panels
8-9 during launch, which led to a considerable thermal
event during reentry.
NlCCOOl.
S,S 107
JofUSBAliD
of i P1, ~
-r i ' \'II~ I':' ~I.l I. Cfll h "1-
"" st /,"v . ~ ,. L>.
'"' '.' ........~~ .' ",. ~o~o • '_ '"o ..~J Jt~
http://caib.nasa.gov
Kennedy Space Center
Engineering and Technology Orbiter Window Debris
Columbia window lying exterior-side up. Photographed at the Columbia reconstruction hangar at KSC on March 3, 2003. Available at http://caib.nasa.gov/
• Cockpit windows and related hardware were among the 84,000+ pieces of
debris recovered after the unfortunate breakup of Columbia.
• Window pane fragments removed from the damaged overhead window
frames were analyzed as part of the Spacecraft Crew Survival Integrated
Investigation Team (SCSIIT) [1]. 4
Kennedy Space Center
Engineering and Technology Crew Survivability Study
• The SCSIIT was chartered to:
Perform a comprehensive analysis of the accident focusing on factors
and events affecting crew survival
- Develop recommendations for improving crew survival for all future
human space flight vehicles.
• A sub-team to the SCSIIT analyzed the effect of the plasma
reentry environment on selected orbiter structural and sub-
structural materials
• The research presented in this talk is discussed in detail in
the following article:
J. D. Olivas, M. C. Wright et ai, Acta Astronautica, Crystallographic oxide
phase identification of char deposits obtained from space shuttle Columbia
window debris; Vol. 67, Issues 5-6, September-October 2010
• This talk will focus on sample preparation and analysis
_ ... c:r.. _
- ....... 1III*t
http://www.nasa.gov/news/reports
/index.html
5
Kennedy Space Center
Engineering and Technology Window Fragments
6
Window 4 ~llNdlt 7 and 8 ".
.LJJJ~........- / ................
r " I. "
'. It r'Z:lJ' _. \
":1/ WyDl~~DJ "D.~fyF \.\ __:J.:.- \
\ "
l /-' i
! ~gF i
r ...... _....-r............ I /
'5- 1 .-, i I .-.. -\_ I ' ':"".----!
.J
--- -Window 11
Window 1
Window 2
Window 3
Inner pressure pane, tempered aluminosilicate
glass, 0.625" thick
Center pane, low-expansion fused silica for thermal
shock, 1.3" thick
- Outer thermal pane, tempered aluminosilicate
glass, 0.625" thick (interior is coated, exterior is not
and withstands 430°C)
• Window fragments were removed from 8
thermal panes.
Concentrated on deposits on Window 8
overhead thermal panes.
Characterization of darkened char that had
deposited on overhead windows.
• The Orbiter windows are comprised of three
panes:
7I 1 em I
Original Magnification: 500X
Char layer Sample Prep & OMKennedy Space CenterEngineering and Technology
A fragment of glass containing
considerable amount of dark "char" layer
on the surface was removed from the
frame for characterization.
Preparation included using cold mounting
two-pour techniques to preserve the char
layer.
- The sample was first completely covered in epoxy
and allowed to cure over night.
- Then the mounted sample was cross-sectioned
and cut to desired shape to reveal the area of
interest.
The second sample was re-mounted using a two-
part epoxy, providing a preserved cross section of
~
the char layer CD
~
Optical microscopy (OM) revealed ~
stratified char layer: ;
.t:
- Bright and reflective constituent near glass 0
interface
Non-uniform, erratically deposited needle-
like constituents in middle layer
- Dark globular constituents throughout
•
•
•
Kennedy Space Center
Engineering and Technology Char layer SEM & EDS
• Scanning electron microscope (SEM) and Energy Dispersive Spectroscopy
(EDS) work characterized layers as:
- Ti-rich oxide material near the glass substrate, reflective layer
- AllTi-rich oxide material away from glass substrate, needle-like (acicular) layer
- Si-rich globules throughout
- Spongy AI layer furthest from glass, likely 2000-series
• Ti deposition being first in sequence of events seemed counter-intuitive:
~ Melting point of AI =660°C
~ Melting point of Ti =1668°C
Need further understanding of deposition event.
Epoxy
. '. I
" A.••. _-..... ; f ~{yf~"DID ',. I
, fJD~ ''i! ~ ~DI ',; .. '-
,,_ ...~I D~t~C}~r ~... ~i.~D r~
,.,..,.1': ~II~~. !l. '. : ~gDI!"I~~. A'"l·"v"AJ?~DiW<A""".".WW . _D;.~vI.•..j.~~.~wD.~"DDDDDDDDWJ~~DJN~DDDD.NFr . - .... ~l.D!DW...I.I.~.... "'''' " •.f'; ........ ~~J D~"I_ lI~I .. _"" ..~y... _ . ""'tt'.f. ,..~.I"~I~IWD~D W"~~~D~~Df~WD~~.D;.~;W~., .;.' 't,~~~~WIt:;I>~.ID~.t{~;to <DWI~;W
'.. . -" t ,.,. .,'ttll • ... • --' .I..~ll~..
. .. .., " ~ • -, .. ~~Pg.WWt
:r' ' .. ,;, . Ia;..._~. ,'14 _, '; , ~~_.. DII~
Aluminosilicate glass
Oriainal Maanification: 500X
~
Q)
~
co
-~
co
.t:
o
Original Magnification: 500X
8
Kennedy Space Center
Engineering and Technology FIB Sample Preparation
• TEM analysis was needed to further characterize the phases in the char layer.
• Optical micrographs were used to determine areas best suited for the TEM:
- Layer thickness
- Constituents at that location (significant amounts of the Ti-rich and AllTi acicular layers)
Original Magnification: 500X, montage
100um
• Platinum was deposited over the Region of Interest (ROI) to protect the layer
from ion damage during focused ion beam (FIB) sample preparation.
---.
Original Magnification: 2000X
Glass
9Original Magnification: 5000X
"
,.n'
Epoxy.'.WW~DWD~~DJJWD:;;N"~".
,1'_"",.J.~~I •.~DW~~......DND!;!~DDDDDDDDD;DDDDDJ ~ ..
.... .~II~ .• lf~ ','. . ...,/ ,~~.W>-Dic~~__I
Kennedy Space Center
Engineering and Technology FIB In-Situ Sample Preparation
• In-situ sample removal:
A rectangular segment was created by milling "trenches" at the
front and back of the ROI with the ion beam
Rectangular specimen was separated by tilting the stage 45°
and using ion beam to cut all sides except one small ligament
Pt is used to adhere specimen to in-situ needle
10
} lOum
char layer
\... ./
"'v"'"
30um
Pt deposition
glass
Kennedy Space Center
Engineering and Technology FIB In-Situ Sample Preparation
Pt depQsition
30um
char layer
"-- "V ~g
~ }
10um
I ~.glass -
.........
• Adhering sample to Cu
grid:
- A TEM copper grid was
snipped to create a horse
shoe shape
- The FIB was used to create a
ditch slightly larger than the
rectangular sample on the
inner radius of the Cu grid
- Rectangular specimen was
positioned inside ditch by
lowering the in-situ needle
and cut free
- Pt deposition was used to
"spot weld" the rectangular
specimen in place
11
Kennedy Space Center
Engineering and Technology FIB In-Situ Sample Preparation
• Specimen thinning:
The FIB was used to thin
out the rectangular
specimen to thickness of
<1000 Ato make it electron
transparent
- As a result of material
removal, the sample took
the shape of an I-beam,
with the thicker regions as
support "flanges"
Specimen was ready for
TEM evaluation
---------
FIB thinning
[] m}lOum
\... Y ./
30um
12
Kennedy Space Center
Engineering and Technology TEM Evaluation
• Specimen inserted in TEM for analysis
• The glass portion of the specimen spanned the "flange"
and "web" of the I-beam
- Between the two regions, there is a transition region (varying
thicknesses)
- A distinction in contrast becomes apparent between the thicker
portions and the thinner portions of the glass phase
Electron
beam
Electron
beam
13
• TEM analysis gave a wealth of information
• TEM images, Selected Area Electron
Diffraction (SAED) and EDS analysis
revealed crystallographic oxide phases
dispersed throughout a glassy matrix
• Regions were referred to as "porous
layer", "outer layer" and "inner layer"
Kennedy Space Center
Engineering and Technology TEM of Char Layer
1 J.lm
Porous
Layer
Outer
Layer
Inner
Layer
}
Glass
Substrate
AI
AllTi
Ti
14
lum
I .
.
Kennedy Space Center
Engineering and Technology
• Elongated crystals further
from the window were a
crystalline aluminosilicate
phase called mullite
(AI4+2xSi2_2xO1o-x)·
- 11 um from glass substrate
- As small as 500 nm x 750 nm
to 1 um x 3.5 J.lm
• Relatively homogeneous
.grains
• Some exhibited skeletal
morphology due to rapid
crystallization from a
silicate melt
Outer Layer TEM
lum
15
Kennedy Space Center
Engineering and Technology Inner Layer TEM
• Crystals closer to the window glass were identified as titanium dioxide
(Ti02l rutile).
- Crystals were equidimensional near glass substrate interface and
appeared in polycrystalline clusters or isolated islands
- Morphology became more irregular further from glass interface
- Crystal size ranged from 300 nm to 1.8 J.!m
16
lum
Kennedy Space Center
Engineering and Technology
Summary of Char Layer TEM
Results
• Found that each region was comprised of crystals dispersed in a
glass matrix (aluminosilicate).
• Crystals closer to the window glass were titanium dioxide (Ti02).
I
• Elongated crystals further from the window were a crystalline
aluminosilicate phase called mullite (AI4+2xSi2-2x010-x).
.-
• 2XXX-series AI was final material to deposit.
lum
7
Kennedy Space Center
Engineering and Technology Temperatures Experienced
• A gradient in glass composition throughout the char layer was used to
determine the temperature at which crystallization occurred.
Components underwent temperatures above 1700°C prior to being
deposited onto the glass substrate.
(l,./lill'l'
fall Call
Xo 582. :.......J '
Paylo,1I1 ~~."J~"""DDD
Crew Windows _ Bay \ E~".IfW.. ~~C ,-." .. ,\\"
olllllalill I • I ._I~.....~"I "Iy~. Atl
.P 1\ • y D
f...., \ rJ; • \ .N.gI.~DyyDt ",wI,,"
R=".. . ~yyy~LiDEJ·-tjl'\lillll ' ............. Body Hap
Conlrol ~. f~~ " ~~JD;~DNffiD" '.. I· - Elevolls
S,"m , • \-'.' r I, I ~ . I 'Module .:t.- "f.DI~ I~>D Ll"r}WN~ 1'1 1;;'-::' .:,f . \'tfJ. ~J ;~.IJ
(
/'l.' ~<WW;WLDf~Dff ,,'\. ''119' ·fJ;q~.WW.rJ~.!..L""
" .. , L~.I "~ ,/.~y.y.\, ;' s~Ij..L"h~ - ~Iny ,::ng EuUe
N,w /.,., .J' M.." ,,,'
Cone' Side WII1U Glawe .X 32\ Hatch Oil Fo' FuuIIIg M,ulllS"lal'e
o ~ Nos" Iwaru "
Gear rlIsdayc
Forward f llselage
Three-zone char layer was only observed on
overhead windows 7 and 8 thermal panes
Majority of structural material surrounding the
overhead windows is 2000-series aluminum.
Payload bay bulkhead latch rollers in close
proximity to the overhead windows and are
composed of titanium alloy Ti-6AI-4V.
Thermal protection system (TPS) nearby is
source for silicon.
•
18
• Microscopic evaluation of a char layer deposited during re-
entry revealed an unexpected sequence of deposition
events.
- Expect AI to deposit first (lower melting point).
• Deposits from a Ti source preceded deposits from other
sources.
- Thermal erosion of suspect Ti-6-4 components was
discovered.
• It was hypothesized that materials deposited on windows 7
and 8 were the result of combustion of a Ti-6AI-4V source
in addition to interaction with surrounding AI and Si
components.
- Exothermic conversion from metallic Ti to oxidized Ti.
- Additional heating beyond aerothermal heating was present.
• Metallic combustion of structural components exposed
to entry environments needs to be a design
consideration in future spacecraft.
- Environmental reactivity of sub-structural material if there is a
chance of comprised thermal protection system (TPS).
Kennedy Space Center
Engineering and Technology Investigation Conclusions
lum
Kennedy Space Center
Engineering and Technology Conclusions relevant to FIB/TEM
• Astronaut Danny Olivas summed it up best:
"The many observations made on a 500 /lm thick layer of char atop
an inconspicuous fragment of the glass which participated in the
Columbia tragedy only serve to highlight the wealth of information
that lies within her debris."
"The nature of the incident and subsequent breakup allow engineers
to learn how to not only make our existing space flight safer, but
provide a greater breadth of core knowledge for the next
generation of rockf3t designers ...as human beings venture go
beyond low earth orbit and on into deep space."
20
Kennedy Space Center
Engineering and Technology Columbia Debris Research
• Columbia debris was made available through the
Columbia Debris Loan Program
• Debris is available to academic institutions by
contacting Richard.W.Russell@nasa.gQY
http://www.nasa.gov/missions/shuttle/columbia_debris.html 2~
Kennedy Space Center
Engineering and Technology Equipment Used in Investigation
• FEI 200 TEM FIB
- 30 kV Ga liquid metal ion source
• FEI Tecnai F30 TEM
- 300 kV FE source, STEM
• JEOL 2500SE FE STEM
- High Angle Annular Dark Field (HAADF)
- X-ray Energy Dispersive Spectroscopy (EDS)
• Zeiss Axiovert Metallograph
• Philips XL 40 FEG SEM
22
Kennedy Space Center
Engineering and Technology References
1. Columbia Crew Survival Investigation Report, National Aeronautics and Space
Administration, SP-2008-565, Washington, DC, December 2008.
2. Columbia Accident Investigation Board (CAlB), Report Volume 1, National
Aeronautics and Space Administration, Washington, DC, August 2003
3. Mayeaux B, McDanels S, et ai, Materials analysis: a key to unlocking the
mystery of the Columbia tragedy", Journal of Materials, February 2004
4. Olivas JD, Melroy P, et ai, OV-102 thermal pane window debris analysis, part
of Spacecraft Crew Survival Integration Investigation Report, NASA
5. J. D. Olivas, M. C. Wright et ai, Acta Astronautica, Crystallographic oxide
phase identification of char deposits obtained from space shuttle Columbia
window debris; Vol. 67, Issues 5-6, September-October 2010
6. Z. Rahman, et ai, Tutorial: In-Situ Site-Selective FIB for High Resolution TEM
Sample Preparation, Microscopy and Analysis, May 2006
7. http://spaceflight.nasa.gov/shuttle/archives/sts-
107/investigation/leftwing/index.html
8. http://caib.nasa.gov/
9. http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_coord.html
23


Utilizing Focused Ion Beam (FIB) and Transmission Electron Microscopy (TEM) for Failure Analysis of Char Deposits Obtained from Space Shuttle Columbia Window Debris

Utilizing Focused Ion Beam (FIB) and Transmission Electron Microscopy (TEM) for Failure Analysis of Char Deposits Obtained from Space Shuttle Columbia Window Debris

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server