generative structural design and optimization of modern ... · stiffener [mm] 20 30 10 bonded...
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This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Generative Structural Design and Optimization of Modern Electric Aircraft
Darmstadt 2019 Bertram Stier
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Outline
2
• Motivation
• Challenge Problem
• Practical Generative Design
• Summary
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Outline
3
• Motivation• Trends
• Industry Reaction
• Challenge Problem
• Practical Generative Design
• Summary
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Trends
4
Source: Urban Mobility Scoreboard, Texas A&M Transportation Institute
Carbon Dioxide Infromation Analysis Center, Global Carbon Project
• Demand for transportation increases quicker than infrastructure expansion
• CO2 emission regulations become more strict
• Lots of time and money ‘wasted’ in traffic
• Congestion and pollution in cities increases
Expanding rail and road is expensive
and might still not meet demands
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Industry Reaction
5
Opportunity: electric urban air traffic
• (Operational) Emission free
• Fast enough
• Indiviual, on demand
• Comfortable, convenient
Challenges
• Regulations (noise, safety, piloting, ...)
• Infrastructure (vertiports, apps, ...)
• Public acceptance
• Viability (economic, range, ...)
Task: Minimize energy consumption per traveled mile. For given system, less total mass translates to less req. enery.
For given energy density (of batteries), decreasing structural mass translates to range or payload increase
Lillium
Audi/Airbus
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Outline
6
• Motivation
• Challenge Problem• Chosen Structure: Wing Section
• A Common Situation
• Practical Generative Design
• Summary
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Selecting Example Structure
7
Lillium
Audi/AirbusBell Nexus
Joby Aviation
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Challenge Problem: Wing Section
8
Conceptual Design Phase
Big part of cost decided
Open design space
Often air foil shape given
Answer fundamental questions
Structural layout (How many ribs)?
Concept (Monolithic/ Sandwich/ Stiffened)?
Material (is it worth paying the extra money)?
Needs to ...
... be light
... be manufacturable
... meet criteria
• Strength
• Stiffness
• Stability
Situation
Lack of information
Not a lot of time
Well founded decisions requires detailed analysis
....is expensive and time consuming
Non-Exhaustive Search
results in
Untapped Potential
worst case: not viable
180 mm
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Design Space, Restrictions and Criteria
9
Property Standard Tape
High End
Tape Fabric
E1t [GPa] 140.0 185.0 56.0
E1c [GPa] 120.0 160.0 52.0
E2t [GPa] 9.0 10.0 56.0
E2c [GPa] 9.0 10.0 52.0
G12 [GPa] 3.4 3.7 2.7
ν12 0.32 0.32 0.10
X1t [MPa] 1820.0 3460.0 735.0
X1c [MPa] 1470.0 1870.0 520.0
Y2t [MPa] 75.0 80.0 820.0
Y2c [MPa] 230.0 280.0 480.0
S12 [MPa] 95.0 160.0 110.0
t [mm] 0.21 0.2 0.3
ρ [kg/m³] 1550.0 1500.0 1550.0
Dimensions Failure CriteriaLayup Rules
(Tape/Fabric)
Monolithic LaminateMin Max Incr Laminate
T [# Plies] 3 50 1 Ply Max Stress1, Stress2, Stress12 Min Max Incr
Ply Tsai-Hahn Interaction %0° 10/0 80/30 20/10
Panel Buckling Uniaxial, Biaxial, Shear %45° 10/0 60/30 20/10
%90° 10/0 50/0 20/0
Sandwich CompositeMin Max Incr Face Sheets
T Top Face [# Plies] 2 8 1 Ply Max Stress1, Stress2, Stress12 Min Max Incr
T Core [mm] 5 20 5 Ply Tsai-Hahn Interaction %0° 10/0 80/10 20/10
T Bot. Face [# Plies] 2 8 1 Core Shear Strength %45° 10/10 50/30 20/10
Panel Buckling Uniaxial, Biaxial, Shear %90° 10/0 50/0 20/0
Composite Hat StiffenedMin Max Incr Skin
T Skin [# Plies] 4 10 2 Ply Max Stress1, Stress2, Stress12 Min Max Incr
T Web [# Plies] 2 4 2 Ply Tsai-Hahn Interaction %0° 10/10 80/30 20/10
T Foot [# Plies] 2 4 2 Section Crippling %45° 10/0 60/0 20/0
T Crown [# Plies] 2 6 2 Local Buckling of Open Span, Closed Span, %90° 10/0 50/0 20/0
H Stiffener [mm] 20 30 10 Bonded Section, Web, Crown Stiffener
Spacing [mm] 100 300 100 Panel Buckling Uniaxial, Biaxial, Shear Min Max Incr
W Foot [mm] 25 - - %0° 0/20 50/80 10/20
W Crown [mm] 30 40 10 %45° 0/20 0/80 0/20
Angle 70 - -
Typical design criteria and layup rules
Typical material parameters
Load Case Tip Deflection
Hovering > 25 mm
Stiffness criterionConcepts
From FAA/EASA, aeroelastics, handling, tooling, maufacturing, analysis, ...
Time consuming to create detailed model for each combination
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
FE Model
10
9000 S4R Elements
Limit Load Factor: 1.2
Ultimate Load Factor: 1.5
Up Gust
Landing
Hovering
Battery pack
Root
Plane Remains Plane
Fixed Reference Point
Tip
Plane Remains Plane
‘Rotor’ Forces
What situation is critical?
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Outline
11
• Motivation
• Challenge Problem
• Practical Generative Design• Practical / Generative
• Structural Optimization Approach
• Procedure
• Traditional Results
• Beyond
• Summary
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Practical / Generative
12
Practical: utilize strengths
Engineer Computer
Creative Does not get bored
Intuition Unbiased
Experience Good memory
Imagination Fast math
Responsibilities/Work shareGuides Provides data
Evaluates Analyses
Generative: Collaborative/interactive
Decisions augmented by insight generated by optimization
Optimization restricted by demands/requirements
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Structural Optimization Approach
13
Equivalent stiffness
Concept Definition Force
Localization
Finite Element Analysis
FEM Update
Mesh
Section Forces
Displacements
Stiffness
Homogenization
Strength Analysis
Local Stability
Panel / Section
Stability Analysis
HyperSizer Smeared Stiffness
Approach
Hyper FEA
CLT
𝐾𝑒𝑙 =𝐴 𝐵𝐵 𝐷
Analytical
Plate
Forces per
ObjectStresses
per Ply
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Procedure Overview
14
Restrict stiffness
modification to Spar Caps
Use Adjoint Variable Design Sensitivity
Analysis to generate stiffness targets per
Element
Optimize Zone Shape
(same design domains)
Use Adjoint Variable Design Sensitivity
Analysis to generate stiffness targets per
Zone
FEA FEA
Splitup wing
skin structure
to components
Define concepts and materials and assign to components
Vary buckling length for
components and size to local
criteria
Choose best rib layout,
concept and material
VBA
FEA
Global Stiffness Target
Final Optimization
Structural Layout, Concept and Material Trade Study
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Stiffness Target Generation
15
during ‚Hovering‘
(Min/Max constraints)
Tip deflection restricted to 20mm in z-direction
Restrict optimization domain Adjoint Variable Design Sensitivity Method
Variable for each FE element
Improve Manufacturability
Zone Optimization (Penalty based target similarity aggregation)
Define Spar Cap zone min- stiffness target Adjoint Variable Design Sensitivity Method
Variable for each Zone
Spar Caps
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Concept, Structural Layout and Material
16
0 Ribs5 Ribs
Finite Element Analysis
Concept Definition Rib Spacing Material Combination
Hyper FEA
Assignment
via script
Load path convergence
Sizing Optimization
to all requirementsAbaqus
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Results – Weight Trends
17
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
Mo
no
lith
ic
San
dw
ich
Hat
Sti
ffe
ned
Mo
no
lith
ic
San
dw
ich
Hat
Sti
ffe
ned
Mo
no
lith
ic
San
dw
ich
Hat
Sti
ffe
ned
Mo
no
lith
ic
San
dw
ich
Hat
Sti
ffe
ned
Mo
no
lith
ic
San
dw
ich
Hat
Sti
ffe
ned
Mo
no
lith
ic
San
dw
ich
Hat
Sti
ffe
ned
0 Ribs 1 Rib 2 Ribs 3 Ribs 4 Ribs 5 Ribs
Wei
ght
[kg]
Standard Material
Top Wing Skins Bottom Wing Skins Leading Edge Trailing Edge
Ribs Monolithic Sandwich Hat Stiffened
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
Mo
no
lith
ic
San
dw
ich
Hat
Sti
ffe
ned
Mo
no
lith
ic
San
dw
ich
Hat
Sti
ffe
ned
Mo
no
lith
ic
San
dw
ich
Hat
Sti
ffe
ned
Mo
no
lith
ic
San
dw
ich
Hat
Sti
ffe
ned
Mo
no
lith
ic
San
dw
ich
Hat
Sti
ffe
ned
Mo
no
lith
ic
San
dw
ich
Hat
Sti
ffe
ned
0 Ribs 1 Rib 2 Ribs 3 Ribs 4 Ribs 5 Ribs
Wei
ght
[kg]
High End Material
Top Wing Skins Bottom Wing Skins Leading Edge Trailing Edge
Ribs Monolithic Sandwich Hat Stiffened
Total weight distribution for different design concepts over number of ribs
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Results - Reasoning
18
Sandwich 0 Ribs Composite Hat 5 Ribs
• Local stability driven
• ‚bad choice‘ of producibility
and tooling constraints
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Best Candidate Evaluation
19
Monolithic – HE – 0 Rigs: 7.16 kg (best: 4.85 kg)
Hat Stiffened – HE –3 Ribs: 4.86 (best: 4.82 kg)
Sandwich – HE –3 Rib: 3.63 kg (best: 3.63 kg)
Mixed Concepts
1 Rib : 3.4 kg
Critical CriterionCritical Load Case
Margin of SafetyBest Concept
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Beyond Traditional
20
Y
XZ
Ny
MxyMx
90s
45s
0s
Ny
MxyMx
Zone Based Ply Based
Required
Plies
Ply Generation
Stacking
From User defined design zones
To Optimized design zone shape
From Zones, Laminate, stacking
To Organic Ply shapes
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Composite Design Setup
21
Ply extension constraintsDesign and Tooling Restrictions
Stength and Stiffness Criteria
Layup and
Stacking Preferences
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Design Optimization Process
22
CAD Init FEA HyperSizer
FEA Run
Update loads
Import and Size
Strength
Stiffness
Stability
Automatic
loop
Tight Coupling with FEA
HyperSizer
Setup Ply
Optimization
Review
Export
Complex Section ShapesPly Shapes
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Free Form Ply Shapes
23
Native Catia Geometry
- Points
- Splines
- Smooting
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Review and Report and Archive
24
Margin of Safety
Critical Criterion
Final Weight 2.7 kgBest Uniform Design per Panel: 3.4 kg
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Outline
25
• Motivation
• Challenge Problem
• Practical Generative Design
• Summary
This presentation and its contents are Copyright © Collier Research Corporation 2019. Do not disclose without written permission.
Summary
26
• Demand from trends / observations
• Actively generated ideas to meet demands
• Definition of requirements and design space
• Practical, generative design exploration
• Structural analysis approach
• Interactive design exploration
• Effective informed decisions
• Best design analysis
• Beyond traditional
?
!
Questions
Requirements
Answers
Design
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