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Current Progress on the Design and Analysis of the JWST ISIM Bonded Joints
for Survivability at Cryogenic Temperatures
Andrew Bartoszyk, Swales Aerospace
FEMCI 2005 Workshop
May 5, 2005
A. Bartoszyk/Swales FEMCI Workshop – May 5, 2005 2
JWST/ISIM Stress Team
Andrew Bartoszyk, Swales Aerospace – Stress Analysis
John Johnston, NASA GSFC – Analysis Lead
Charles Kaprielian, Swales Aerospace – Stress Analysis
Cengiz Kunt, Swales Aerospace – Stress Analysis Lead
Joel Proebstle, Swales Aerospace – Stress Analysis
Benjamin Rodini, Swales Aerospace – Composite Materials
Daniel Young, Swales Aerospace – Stress Analysis
A. Bartoszyk/Swales FEMCI Workshop – May 5, 2005 3
Design and Analysis Challenges
• Design Requirements– Metal/composite bonded joints required at a number of nodal locations on
the JWST/ISIM composite truss structure to accommodate bolted instrument interfaces and flexures.
– Survival temperature at 22K (~ – 400oF); – 271K total T from RT.– Composite truss tube with high axial stiffness (~23 msi) and low axial CTE
(~ 0 ppm/K).– Multiple thermal cycles throughout design life of structure. In order to
survive launch loads, joints cannot degrade more than an acceptable amount.
• Design/Analysis Challenges– Large thermal mismatch stresses between metal fitting and composite tube
at cryogenic temperature (22K).– Analysis and design experience is very limited for metal/composite bonded
joints at temperatures below liquid nitrogen (~80K).– Thermo-elastic material properties and strengths for composites and
adhesives at 22K are not available and difficult to test for.
A. Bartoszyk/Swales FEMCI Workshop – May 5, 2005 4
T-Joint (Gusset & Clips)
Saddle
Plug
ISIM Basic Joint Assemblies
A. Bartoszyk/Swales FEMCI Workshop – May 5, 2005 5
Basic Plug Joint Details
Metal Fitting (Invar 36)E = 18.8 msi = +1.5 ppm/K
Hybrid Composite Tube Eaxial = 23 msiEhoop = 6.7 msiaxial = -0.13 ppm/Khoop = +3.7 ppm/KSzz = 2.9 ksi (20 MPa)Szx = Syz = 5.8 ksi (40 MPa)
Adhesive Bond (EA9309)E = 1.1 msiG = 0.4 msi = 47.8 ppm/KFsu = 11.6 ksi (80 MPa)
• Stiffness and strength properties are given for 22K.• Thermal expansion properties are secant CTE from RT to 22K.
75 mm square composite tubew/ nominal 4.6 mm wall thickness interlaminar
strengths
A. Bartoszyk/Swales FEMCI Workshop – May 5, 2005 6
Composite Modeling and Mesh Size
• Mesh size: 2.5 mm square in-plane
• Surface plies at bonded interfaces modeled individually
• Aspect ratio 2.5/0.071 35
• Laminate core modeled with thicker elements
• Adhesive modeled with one element through the thickness
• Same mesh size used in all joint FEMs including development test FEMs
• Stress recovery: Element centroid for interlaminar, corner for others
View A-A
Symm
etry
Con
strain
t
Symmetry Constraint
Ply 1 – Explicit Props (T300/954-6 Uni Ply)Ply 2 – Tube Smeared Props (T300/954-6 Uni Ply)Ply 3 – Tube Smeared Props (M55J/954-6 Uni Ply)
Ply 1Ply 2Ply 3
x
y
Adhesive (0.3 mm thick)
Invar Fitting
A. Bartoszyk/Swales FEMCI Workshop – May 5, 2005 7X Y Z( )
F33
F13 > FRSS > F23
F23
FRSS
33
13
23
Lamina Failure Criteria – Bonded Joints
12
23
23
2
13
13
2
33
33
FFF
Design Space
F13
33
1122
13 / 23 = 1.5
122
33
33
RSS
RSS
FF
Under thermal loads, metal/composite bonded joints typically fail in composite interlaminar stresses.
A. Bartoszyk/Swales FEMCI Workshop – May 5, 2005 8
Interlaminar Failure Prediction
An empirical Interlaminar Failure Criterion is used for critical lamina:
where 33 is peel stress, rss is resultant transverse shear stress, and F terms are
material constants dependent on interlaminar strengths, which are being determined by testing.
FRSS
RSS
F33
33
122
33
33
RSS
RSS
FF
State 1(peel-shear interaction)
State 2(compressive normal and shear)
Margin Calculations
Stress State 1
Stress State 2
1
RSS
RSS
FS
FMS
11
22
33
33
RSS
RSS
FFFS
MS
A. Bartoszyk/Swales FEMCI Workshop – May 5, 2005 9
Bonded Joint Design & Sizing Flow
Preliminary Design: Tube Layout, Cross Section,
Laminate, Joint CAD Concepts
Preliminary Basic DesignThermal Survivability SFc > 1.0 (> 1.5 Goal)
Identify Basic Joint Elements: Plug, Saddle, T-Joint
Concepts
Estimate Cryo Properties
Phase 1BDouble Strap Design
Phase 1BDouble Strap Testing
Material Characterization
Correlate Cryo Properties
& Revise Analysis
Optimize BasicDesign MS > 0
Preliminary Basic DesignLaunch Loads
MS > 0
“Good” SFc
Calculate & Envelope Joint Launch Loads
Verify UnderGH&T Loads
Phase 1C – Strength Degradation Testing
Phase 2 – BreadboardJoint Testing
Flight Joint Detailed Design & Analysis
no
yes
START
FINISH
FS – Factor of Safety (Requirement)SFc – Calculated Safety FactorMS – Margin of Safety
SFc = Allowable/StressMS = SFc/FS - 1
A. Bartoszyk/Swales FEMCI Workshop – May 5, 2005 10
Bonded Joint Analysis Correlation - Procedure
X
Y
Z
V1
X
Y
Z
V1
X
Y
Z
3.564 1.969 0.373 -1.223 -2.819 -4.415 -6.011 -7.607 -9.203
V1G5
Output Set: 19K & -9.096kNContour: Solid X Normal Stress
X
YZ
16.69
14.72
12.75
10.77
8.802
6.83
4.857
2.885
0.913
-1.06
-3.032
-5.004
-6.976
-8.949
-10.92
-12.89
-14.87
V1G5
Output Set: 30K & 150MPaContour: Solid X Normal Stress
3. Test Coupon Analysis
5. Flight Joint Analysis
Test Failure Load(Mech & Thermal)
Design Limit Load(Mech & Thermal)
4. Failure Curve
2. Coupon Testing
1. Coupon Analysis& Design
(Match Flight Joint Critical Stresses)
-15.0
-10.0
-5.0
0.0
5.0
10.0
15.0
20.0
25.0
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0
Interlaminar RSS Shear (MPa)
In
terl
am
inar
No
rma
l (M
Pa
)
ISIM Basic Joints
M55J/954-6 Failure Curve (RSS shear)
GussetSF = 1.52
SaddleSF = 1.92
ClipSF = 1.54
PlugSF = 2.04
-15.0
-10.0
-5.0
0.0
5.0
10.0
15.0
20.0
25.0
0.0 10.0 20.0 30.0 40.0 50.0 60.0
Interlaminar Shear (MPa)
In
terl
amin
ar N
orm
al (
MP
a)
Test Data (Average)
Assumed Failure Curve (90deg shear)
Assumed Failure Curve (0deg shear)
Assumed Failure Curve (RSS shear)
FWT Test @77KSaddle DSJ Peel Test @19K(90deg direction shear)
Saddle DSJ Shear Test @19K(90deg direction shear)
A. Bartoszyk/Swales FEMCI Workshop – May 5, 2005 11
Basic Plug Joint Detailed Stress Analysis
Node Count – 5,570DOFs – 16,710
1/16 Slice
Phase 2 Plug Joint
ISIM Plug Joint
A. Bartoszyk/Swales FEMCI Workshop – May 5, 2005 12
Basic Plug Joint - FEM
A
A
View A-A
Symm
etry
Con
strain
t
Symmetry Constraint
Symmetry Constraint
Ply 1 – Explicit Props (T300/954-6 Uni Ply)Ply 2 – Tube Smeared Props (T300/954-6 Uni Ply)Ply 3 – Tube Smeared Props (M55J/954-6 Uni Ply)
Ply 1Ply 2Ply 3
zy
x
x
y
Adhesive (0.3 mm thick)
A. Bartoszyk/Swales FEMCI Workshop – May 5, 2005 13
Basic Plug Joint - Applied Loads
Load Case
Type T (K) Fz (N) Remarks
1 Thermal -271 0 RT to cold survival temperature (22K)
2 Thermal & I/F & 1g -271 4513 Thermal plus worst case tension (I/F & 1g) and worst case compression (I/F & 1g)3 Thermal & I/F & 1g -271 -9096
4 Launch 0 83200
Absolute max axial load from ISIM beam element model loads run (includes additional effective axial load due to moment load)
Fz(applied as pressure load on face)
Symmetry Constraint
z
x
A. Bartoszyk/Swales FEMCI Workshop – May 5, 2005 14
Basic Plug Joint - Margin Summary
Load Case Failure ModeAllowable
(MPa)Abs Max
(MPa)MS Comments
Thermal & Mechanical
(-271K + I/F + 1g)
Ply-1 (T300) - interlaminar + 0.40
Ply-3 (M55J) - interlaminar + 0.32
Invar (Blade)
VM yield 275 115 + 0.91 assume strength properties at cryo to equal properties at room temperatureVM ultimate 414 115 + 1.57
Launch
Ply-1 (T300)
- interlaminar + 0.92
s11 1380 162 + 3.73 max corner stress. allowables are based on explicit props. s22 81 12.4 + 2.63
Ply-3 (M55J) - interlaminar + 0.38
Tubes11 439 157 + 0.55 max corner stress. allowables are
based on tube smeared props.s22 241 42 + 2.19
Invar (Blade)
VM yield 275 167 + 0.32 max corner stress in blade, localize stress raisers at blade/hub interface not includedVM ultimate 414 167 + 0.77
• Margins presented at PDR, Jan 2005.
A. Bartoszyk/Swales FEMCI Workshop – May 5, 2005 15
X
Y
Z
3.564 1.969 0.373 -1.223 -2.819 -4.415 -6.011 -7.607 -9.203
V1G5
Output Set: 19K & -9.096kNContour: Solid X Normal Stress
X
Y
Z
22.66 19.83 17. 14.17 11.34 8.508 5.678 2.848 0.0178
V1G5
Output Set: 19K & -9.096kNContour: Solid XY Shear Stress
xx (MPa)
z
y
RSS (MPa) Invar fitting
Invar fitting
MS = +0.32(shear dominated failure)
Basic Plug Joint
Ply 3 Interlaminar Stress Plots – Thermal & I/F
A. Bartoszyk/Swales FEMCI Workshop – May 5, 2005 16
SF and Failure Curve – Basic Joint Assemblies
-15.0
-10.0
-5.0
0.0
5.0
10.0
15.0
20.0
25.0
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0
Interlaminar RSS Shear (MPa)
In
terl
am
ina
r N
orm
al
(MP
a)
ISIM Basic Joints
Assumed Failure Curve (RSS shear)
GussetSF = 1.52
SaddleSF = 1.84
ClipSF = 1.54
PlugSF = 1.99
A. Bartoszyk/Swales FEMCI Workshop – May 5, 2005 17
DSJ Test Data and Estimated Failure Curve
F13FRMSF23
Clip Peel& Shear D/S
Clip Shear D/S
-15.0
-10.0
-5.0
0.0
5.0
10.0
15.0
20.0
25.0
0.0 10.0 20.0 30.0 40.0 50.0 60.0
Interlaminar Shear (MPa)
Inte
rlam
inar
No
rmal
(M
Pa)
B-Basis Data
ISIM Basic Joints
2,3 Failure Curve (90deg shear)
1,3 Failure Curve (0deg shear)
RSS Shear Failure Curve
FWT
Double-Strap Peel 900
Double-Strap
Shear 900
F23 FRSS F13
A. Bartoszyk/Swales FEMCI Workshop – May 5, 2005 18
Remarks and Conclusions
• Material characterization testing and joint development testing are in progress. Test results will be critical for analysis correlation and the final design/analysis of the ISIM metal/composite bonded joints.
• A Phase-2 test program is underway and will include thermal survivability testing of basic joints including a plug joint.
• An evaluation of strength degradation due to multiple thermal cycles will also be included in the joint development test program.
• The ISIM Structure successfully passed PDR (Preliminary Design Review) in January 2005, design requirements have been met. Critical Design Review is scheduled for December 2005.
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