Cost/Weight Optimization of Aircraft Structures - Galorathgalorath.com/.../08/5_-_Markus_Kaufmann_-_Cost_weight_optimizati… · Need for Weight Savings – Fuel consumption of an

Cost/Weight Optimizationof Aircraft Structures

Markus Kaufmann

Kungliga Tekniska Högskolan

Outline

• Motivation

• Aim of this work

• Multiobjective Optimization

• Paper A-C

• Future Work

Fuel Price

Data provided byNordea Bank AB

Need for Weight Savings

– Fuel consumption of an A330– 0.035 l/seat/km – Average gross weight 200 tonnes– 25 years, 300 days, 2·6000 km each day– 100 million km– 250 seats

– 1 billion liters of jet fuel– 5000 liters per kg gross weight– 1500-2000 € per kg gross weight at €0.4/l

Composites vs. Metals

Spec

ific

stre

ngth

σ/ρ

Specific stiffness E/ρ

100

150

200

250

300

0

50

0 5 10 15 20 25 30 35 40

Glass/QI

Carbon/QI

Titanium

Magnesium

Steel

Aluminum

F.P. Beer and E.R. Johnston: ”Mechanics of Materials”,

McGraw Hill, 1992.

Switch to Composites

By courtesy of H. Assler,Airbus Deutschland GmbH

Com

posi

te S

truct

ura

lW

eight

[%]

A300 A310-200

A320

A340-300

A340-600

A380

A400M

A35050

40

30

20

10

0

1970 1975 1980 1985 1990 1995 2000 2005 2010

Composites vs. Metals

Main advantages– Specific strength and stiffness– Less corrosion– Less fatigue problems, saving maintenance– Composite can reduce the number of parts and fasteners

But– Composite structures are more expensive to design

and to manufacture– Problems with the manufacturing of thick structures– Rigorous non-destructive necessary– Barely visible impact damage (BVID)– Complex damage tolerance mananagement

Life-Cycle Cost

Marx et al.: ”A knowledge-basedsystem integration with numericalanalysis tools for aircraft life-cycle

design”, Artificial Intelligence for Engineering Design, Analysis and

Manufacturing, 12:211-229, 1998.

Life Cycle Cost

AcquisitionCost

Weight, Operating Cost

Minimum LifeCycle Cost

Cost

Reliability/Performance

Aim of this work

Development of a cost/weight optimisation framework for aircraft structures

a) applicable for a variety of structuresand manufacturing processes

b) arbitrarily expandable (e.g. for the introduction of a novel NDT cost module, or the sub-optimisation of manufacturing parameters)

Multiobjective Design Optimization

• Goal programming (min Cman) or(min Weight)

• Pareto Optimality

• Minimizingweightedsums

CostW

eight

XX

X

XXXX

Direct Operating Cost (DOC)

DOC = Cflight + Cmaintenance + Cdepreciation + Clnr + Cfinance

with Cflight = f(crew, fuel, insurance)Cmaint = f(maintenance, repair, overhaul)Cdepr = f(price, flight hours)Clnr = f(landing and navigation fees, registry taxes)Cfin = f(financing strategy)

J. Roskam: ”Airplane Design Part VIII”,DARcorporation, 1990

Paper A

• Cost/Weight Optimization for different weight penalties

• The skin/stringer element

• Objective functionDOC = Cman + p*W with p = lifetime fuel burn cost

component weight

Paper A

weight

FEABAQUS

DOC

solver

+

design

constraints

objective function

CmanSEER-DFM

Low-weight design

Low-cost design

Paper A

composite skincomposite stiffeners

end user

part supplier

Paper A

paretofrontier

Paper A

all-metal mixed

The first conclusions

– more costs that describe the aircraft’s life-cycleshould be included

– non-destructive testing

– maintenance and overhaul

NDT module

Input: - type and geometry of the feature- quality level (flaw size)- prescribed probability of detection (POD) - nominal strength

Output: - NDT cost- adapted scan pitch dk

- reduced strengthdk

lk

wk tk

NDT module

• Flaw sizes of less than 6mm can be applied, giving » higher NDT cost » thinner structure due to higher strength » lower structural weight and manufacturing cost

• Flaw sizes of more than 6mm can be applied, giving» lower NDT cost» thicker structure due to lower strength» higher structural weight and manufacturing cost.

Paper B

CmanSEER-DFM

weight

design

FEABAQUS

DOC

Xopt

dkNDT

Paper B

• The skin/stringer element

• Division into 17 NDT features (i.e. laminates, radii and bonds)– NDT cost– scan pitch– material strength

• Objective function– DOC = Cman + Cndt,prod + 5 Cndt,serv + €1500/kg*W

Some more conclusions

• Optimization of Direct Operating Cost including NDT

• Embedding of quality management into the design phase

– Fine/coarse NDT scanning where necessary

– High/low security factors where necessary

• The next step towards the optimization of thetotal life-cycle

– Cman, Cdepr, Cmaint

• But: Not the lowest manufacturing cost possiblefor each given geometry

Paper C

Markus Kaufmann, Thomas Czumanski and Dan Zenkert: ”Manufacturing Process Adaptation for the Integrated Cost/Weight

Optimization of Aircraft Structures”Submitted to ECCM-13, 2008

Design solutions

DOC

Manufacturingprocess adjustments

DOC*

Future Work I

FE

DOC / LCC

solver

structuraldesign

constraints

objective function

Pollutant Emissions

Future Work II

FE

DOC

solver constraints

objectivefunction

structuraldesign Cutting of prepregs,

layup, draping,curing

Thank you for your attention.

Appendix: NDT Module

Input: - type and geometry of the feature- quality level (flaw size)- prescribed probability of detection (POD) - nominal strength

Output: - NDT cost- adapted scan pitch dk

- reduced strengthdk

lk

wk tk

NDT modulePro

babili

tyof D

etec

tion

Flaw size [mm]

thick laminate

thin laminate

flaw size 6mmscan pitch 2mm PODmin 95%allowable 0.40% εcompr

NDT module

thick laminate

thin laminate

Pro

babili

tyof D

etec

tion

Flaw size [mm]

flaw size 5mmscan pitch 2mm PODmin 75%allowable 0.38% εcompr

NDT modulePro

babili

tyof D

etec

tion

Flaw size [mm]

thick laminate

thin laminate

flaw size 5mmscan pitch 1mmPODmin 95%allowable 0.38% εcompr

xxxxTotal

XxXx8Level 1PE autom040400['F17'] = 'Bond Stiffener2

XxXx8Level 1PE autom040400['F16'] = 'Bond Stiffener1'

XxXx0.4Level 2PE manual8--400['F15'] = 'Str2 Radius 4'

XxXx0.4Level 2PE manual8--400['F14'] = 'Str2 Radius 3'

XxXx0.4Level 2PE manual8--400['F13'] = 'Str2 Radius 2'

XxXx0.4Level 2PE manual8--400['F12'] = 'Str2 Radius 1'

XxXx10Level 1TT autom-550400['F11'] = 'Str2 Vertical Web'

XxXx8Level 1TT autom-540400['F10'] = 'Str2 Horizontal Foot'

XxXx8Level 1TT autom-540400['F9'] = 'Str2 Horizontal Flange'

XxXx0.4Level 2PE manual8--400['F8'] = 'Str1 Radius 4'

XxXx0.4Level 2PE manual8--400['F7'] = 'Str1 Radius 3'

XxXx0.4Level 2PE manual8--400['F6'] = 'Str1 Radius 2'

XxXx0.4Level 2PE manual8--400['F5'] = 'Str1 Radius 1'

XxXx10Level 1TT autom-550400['F4'] = 'Str1 Vertical Web'

XxXx8Level 1TT autom-540400['F3'] = 'Str1 Horizontal Foot'

XxXx8Level 1TT autom-540400['F2'] = 'Str1 Horizontal Flange'

XxXx120Level 2Squirter-5600400['F1'] = ‘Skin Laminate'

Cost [€]Time [min]Path [m]OperatorTechniquertWLFeature

Length 400mm Total width ofPitch: 300mm the panel is Panel thickness: 5mm 2*pitchWeb height: 50mmFlange width: 20mmProfile thickness: 5mm

Appendix: NDT Module