NASA Technical Reports Server (NTRS) 20160010278: Fused Silica and Other Transparent Window Materials

3.1 MB·English

by  NASA Technical Reports Server (NTRS)

National Aeronautics and Space Administration
Fused Silica
and
Other Transparent Window Materials
Jon Salem
NASA Glenn Research Center
Cleveland, Ohio
ICACC, Daytona Beach, January 27th, 2016
Advanced Ceramics Laboratory Life Prediction Branch 1 www.nasa.gov
National Aeronautics and Space Administration
Outline
 Window Applications and Requirements
 Historical Material
 New Materials and Mechanical Properties
 ISS Windows and Damage
 Anomalous Behavior of Silica
 Comparison to Published Literature
 Conclusions
Advanced Ceramics Laboratory www.nasa.gov
2
National Aeronautics and Space Administration
Some NASA Window Applications
www.nasa.gov
3
National Aeronautics and Space Administration
Fused Silica – Workhorse Material
• Fused silica has been the historical material of
choice:
– Apollo
– SkyLab (73-74) , Mir…
– ISS (98-xxxx)
– Shuttle
– Orion
• Only one unexpected failure during an Apollo window
proof test.
www.nasa.gov
4
National Aeronautics and Space Administration
Window Requirements
• Thermal shock
• Mechanical (crack growth)
• Optical (haze, transmittance…..imagery, piloting)
• Chemical (atomic oxygen, radiation..)
• Impact residual strength (handling, hyper)
• Big advantages are optical and thermal.
• But why windows at all?! Psychological.
www.nasa.gov
5
National Aeronautics and Space Administration
Windows in Use - ISS
Most famous are the Cupola windows, which are shuttered:

More typical widow (10”):

HITF White Sands STS-84 Atlantis
1 mm
Some windows are not shuttered and can be damaged by MMOD….

www.nasa.gov
6
National Aeronautics and Space Administration
New, Impact Resistant Materials
• A variety of “new” materials have been developed or
re-developed:
-
AlON
19”
- Spinel
- MgO, Alumina, glass-ceramics
24”
• One driving force has been military armor:
Fused Silica - 35 lbs/ft2
ALON - 17 lbs/ft2
Comparable Performance
• Might these materials work for spacecraft windows?
www.nasa.gov
7
National Aeronautics and Space Administration
Property Comparison
 
1 v 
• Thermals shock related: R''  c
EC
p
Material Young's Fracture
CTE x Thermal Heat R R’’
Modulus Strength 10-6/oC Conductivity Capacity (K) (Wcm2
GPa (MPa)  (W/mK) λ (J/gK) /gK)
Silica 72 80 0.5 14 0.77 1733 143
Spinel 270 80 6 15 0.88 73 3.5
(coarse grain)
Spinel 270 160 6 15 0.88 73 3.5
(fine grain)
AlON 314 210 5 13 0.92 99 3.8
• Positive: similar thermal conductivity.
• Negative: new materials have higher CTE.
 Poor thermal shock.
www.nasa.gov
8
National Aeronautics and Space Administration
Mechanical Property Comparison
• Crack growth related:
Material Density Young's Fracture Crack Fracture
(g/cc) Modulus Toughness Growth Strength
(GPa) (MPam) Exponent, n MPa
Silica 2.2 72 0.75 24 80
Spinel 3.6 270 1.5 22 80
(coarse grain)
Spinel 3.6 270 2.0 50 160
(fine grain)
AlON 3.7 314 2.2 35 - 50 210
• Positive: New materials are tougher and SCG resistant.
• Negative: New materials are denser and stiffer.
www.nasa.gov
9
National Aeronautics and Space Administration
Slow Crack Growth Curve
• The SCG curve captures much of the mechanicals:
Material Density
(g/cc)
Silica 2.2
Spinel 3.6
Spinel 3.6
AlON 3.7
• Does not account for weight…….
www.nasa.gov
10