optimization assisted concept design of aircraft floor structures
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Optimization Assisted Concept Design of Aircraft Floor Structures
Wolfgang Machunze
09. November 2011
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• Project scope
• Concept idea
• Using HyperWorks concept design phase of innovative PAX floor structure
Sub modelling technique
Free size optimization
Sizing of composite cross beam
Parameterisation of CAD models CATIA V5 - Hypermesh morphing
Shuffle optimization – Stacking rules
• Manufacturing of sized cross beam structure
• Pax floor design status
• Outlook
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Outline
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Optimization assisted concept design of aircraft floor structures
Scope:
Pax floor within typical fuselage area of
reference A/C NGA
Concept targets:
• Weight saving
• Pax floor height reduction
• Modularization – pre equipped structures
• Low cost manufacturing
Pax floor design driver:
• Statics, dynamics
• Attachment points (seat rails, z-strut)
• System installation
Pax floor
A
A
Section cut A-A
Project scope
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Reference - CFRP Concept idea - CFRP
Basic concept idea:
• CFRP cross beam concept with systems below cross beam
minimize PAX floor height and structure weight
• Improve maintainability in flight and enable modularization
during assembly of PAX floor
• Use manufacturing approach braiding to realize cranked cross
beam systems within cranking area
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Concept idea
Systems
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• Sizing of sub components within global aircraft FE-model with realistic surrounding loads,
stiffness and boundary conditions
• Reduction of simulation time by using superelement approach:
surrounding structure (red) represented by KAAX & PAX matrix
• Check of approach: Displacement for dimensioning load case of cross beam structure
“Rapid Recompression” (typical fuselage section 16/18)
Optimization assisted concept design of aircraft floor structures 14 November, 2011
Sub modelling technique
Global FE ISSY model Sub model with KAAX & PAX
Surrounding aircraft structure
Sub model for PAX floor sizing
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Cross beam - dimensioning load cases
• 8 load cases considered within sizing
process for cross beam structure
Design mainly driven by bending loads
• Ground Loads
Symmetrical landing case
• Gust Loads
Continuous turbulences lateral
• Failure Loads
Rapid decompression up
Rapid decompression down
• Double inner pressure – tension loads
Symmetrical landing
Turbulence lateral
Rapid decompression down Rapid decompression up
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• Using free size optimization for first concept weight comparison using
homogeneous material
Stiffness constraint
Minimum mass
• Detection of high loaded area using free size optimization and
comparing with analytic course of moments and transverse forces
• According to results modification of cross beam design
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Free size optimization - Concept development
Course of
moments over
cross beam
De
sig
n p
rocess
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Sizing optimization
• CFRP sizing optimization considering manufacturing constraints with target robust design
• Span direction 4 varying areas with differing design variables
– By equations forced to minimized thickness steps within cross beam to reduce
manufacturing effort
– Crossbeam:
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• Stiffness
• Stress
– Max-Stress criteria:
• Strain
– Evaluated via 2 equations:
• Stability
• Manufacturing constraints
• Laminate stacking rules
– Percentages to meet the rules in later shuffle optimization
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Sizing optimization - constraints Mid-point
LC 574 LC 576
Max. deflection
allowed [mm] + xx,xx mm - xx,xx mm
^
1c 1 ^
1t
2
12
2
1
00.000.0
1:
xxxx
IMA
Modes Eigenvalue range
15 0.05 < λ < 3
Y
Z
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Shape Optimization – Shear centre
Force
Shape
• Consideration of shear centre within optimization
steps using design variables and equations
Prevent crossbeam twist
• PAX floor panel nodes from ISSY-model used for
load introduction node coordinates need to be
modified by actual shear centre
• Steps for integration:
1. Equation for shear centre:
2. Shape variable for node within realistic range
5 mm < Shape < 15 mm
3. Scaling of shear centre
4. DLINK2 to link shape DESVAR with scaled
shear centre
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h
btth
bt
f
w
f
SC6
3 2
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Shape variable Minimum principal strain • Shape optimization within critical
cranking area to reduce
compression strain within
flanges
• Design variable: Shape
• Objective: Max. Min. Principal
Strain
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Shape optimization of cranking area
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• Transfer of sizing results into stacking sequence considering stacking rules defined by
Airbus
• Easy tool to stack complex results in manufacturable order
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Shuffle optimization
Super Ply level Stacking
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• Morphing basing on parametric CATIA V5 models mesh and connection elements
(MPC, RBE2) can remain only map to geometry
• Design study within first project steps possible
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Model variation by morphing
Reference CCB-A Simple crank CCB-B Several crank
Concept
Deviation
Weight
100 % 103,8 %
111,3 %
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Weight/frame bay Reference NGA CCB
Cross Beam [%] 100 104
Bracket (LT) [%] 100
(aluminium brackets radius)
300
(aluminium brackets radius + bracket free side)
Floor panel [%] 100 110
Inner false rails [%] 100 0
Total weight 100 102
Weight analysis – aircraft level
• Weight analysis must be done on aircraft level
No inner false rail necessary
Minimal thicker floor panels
Slight weight increase for cross beam
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PAX floor concept – current status
• Next to structural design also system
architecture important for PAX floor concept
• Target: combine structural optimization with
target of optimal system architecture
CCB – system architecture
CCB – no inner false rail necessary
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Manufacturing of 4,5 m cross beam structure
Winding of 4,5 m cross beam Braiding of 4,5 m cross beam
UD-layer
Infiltration of 4,5 m cross
beam on CFRP tool within
ECD-Autoclave as VAP
process
Very good quality of
infiltrated cross beam
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Summary & Outlook
• Achievements for current project status:
• Optistruct with its tools can be used for
various tasks
• Static testing of cross beam structure
according to pressure load distribution of
cross beam structure validation of
numeric results
• Fuselage demonstrator with innovative
PAX and Cargo concepts in 2012
Weight saving
Pax floor height
reduction
Cost reduction
System
installation
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Wolfgang Machunze
+49 (0) 89-607 29580
Thank you for you attention!
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