Concept Design of a Composite

Aircraft Door

An integratedapproach to structural and MBS optimization

25th July 2007

Presentation Overview

Model: experimental door developed for Composite FuselageDemonstratorObjective: assess potential of an optimization-driven design in termsof weight saving and development timePresentation consists of 5 parts

Model description and overall optimization approachOptimization of door structureMBS optimization of opening/closing mechanism.Optimization of interface between mechanism and door structureConclusions

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Optimization Activity Framework

„KinematicBoxes“

DoorStructure

Mechanism

Free SizeOptimization

Decompositioninto areas with

different plystackings

M.B.S. Optimization

Minimization of loads

transferred to structure.

FINAL MODEL INTEGRATION AND FINE TUNING

TopologyOptimization

Basic geometric

layout

Problem: simultaneous optimization of all subcomponents notfeasible.Solution: preliminary optimization of single components followed byintegration and fine tuning

DoorStructure

Free-SizeOptimizationOverview

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Optimization of Door Structure

PRELIMINARY STRUCTUREFrame-beam-stringerconfiguration frozen

LOADSMainly inner pressure

REQUIREMENTS•Principal Strainallowables•No buckling•Max displacementsat skin.

FREE SIZE COMP. OPTIMIZATIONDetermination of optimum overall thickness of 0o, ±45o, 90o layers for each element.

MODEL SUBDIVISIONSubdivision of model in areas with different layups.

SIZE OPTIMIZATION 1/2: LayUp CompositionOptimum # of 0o, ±45o, 90o plies for each layup.

SUBCOMPONENT READY FOR INTEGRATION AND FINE TUNING

Shape optimizationPly stacking optimization

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Door Struct. Opt.: Free Size Opt. Input

Subdivision of structure into layupareasObj: min. weighted complianceConstraints:

massbucklingmajor princ. strainsmax outward displacement

Design Variables:Stiffner elements: thck of the 3 plies (0o, 90o, ±45o)Skin elements: thck of the 2 woven plies (at 0o and 45o to flightdirection)

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Door Struct. Opt.: Free Size Opt. Results, Skin

Thk of PLY 1 (// to flight dir.) Thk of PLY 2 (45o to flight dir.)

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Door Struct. Opt.: Free Size Opt. Results, Stiffeners

0o direction stiffener-wise.From above left, clockwise:

•Thk. of ply 1 (0o)

•Thk. of ply 2 (90o)

•Thk. of ply 3 (±45o)

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Door Struct. Opt.: Structure Subdivision

Tradeoffbetween light weight and easeof production. Early involvmentof design and manufacturingstronglyadvisable.

Mechanism MBS OptimizationOverview

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MBS Opt.: Design Variables

Position of joints

Stiffness, diameterand position of torsion spring

Idealization of mechanism intoMBSVariation of position of jointsTorsion spring paramenters

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MBS Opt.: Results

Progressive reductionof maximum forcesover the course of optimizationLoads transferred to structure were also reduced.20% violation of maxforce constraint still present to be dealt with in fine tuningphase withinintegrated model

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MBS Opt.: Results

Intermediateconfiguration

Final configuration to be included in integratedmodelBaseline

design

„KinematicBoxes“

TopologyOptimizationOverview

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Optimization of Kinematic Boxes

DESIGN SPACE

LOADSFrom MBS optimization

MANUFACT. CONSTRAINTSMilling process from 2 opposing directions

REQUIREMENTS•Max VM stress•Lateral stiffness at bearings

TOPOLOGY OPTIMIZATION

„LEGO MODEL“Elimination of elements with lowestdensities

GEOMETRY REFINEMENTCreation of new CAD Model

Updated FE model

SUBCOMPONENT READY FOR

INTEGRATION AND FINE TUNING

Further topology opt.

Shape opt.

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Cineamtic Housings Opt.: Loads

Loads extracted fromMBS optimization of cinematic6 L.C. consideredcovering handle excursion. Additional L.C. to assess lateral stiffnessat bearings.

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Cineamtic Housings Opt.: Topology Output

Truss like structures to besubmitted to detailed design(e.g. shape optimization)

Final Remarks

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Conclusions

Key Advantages7-12% weight saving expected from final integration of subcomponentsConsiderable potential for reduction of development time

Main ChallengesOptimization considerably alters status quo in design-stress interaction

challenging implementationOptimization design approach particularly sensible to design-drivinginputs (e.g. manufacturing requirements, loads, interaction with otherparts) robustness of design particularly important.