Development Of An Aero-Structural Optimization Tool For Aircraft

BHE Progress Report4. Dec. 2017Development of an Aero-StructuralOptimization Tool for AircraftDepartment of Aerospace Engineering, Tohoku UniversityMasashi SODE

Introduction Design Problem of CFRP AircraftIntegration problem of multi-disciplinary research fieldsAerodynamicsDesignfaster, longer rangeStructuralDesignLight weight,efficientMaterialsDesignLight, strong, long lifeMulti-scale lti-Scale2 / 15

Introduction The Conventional Design Approach747727Estimated weightof the new aircraftEmpirical design method・ Design by estimation formulaobtained from statistical data・ It is effective for the design ofthe conventional aircraft.・ the problem is that the accuracyto the new concepts is low.ex) new materials (CFRP)New design method is necessaryfor applying new materialsA review of aircraft wing mass estimation methods, Aerosp. Sci. Technol. (2017)3 / 15

Introduction Aircraft Design ToolAnalytical approachWeight estimation by semi-empiricalstructure design using theoreticalequationElham et al., AIAA 2014Numerical approachLarge scale optimizationwith simulationsMartins, Kenway et al., AIAA 2014there are still no examples of aircraft design toolsthat can consider the multi-scale properties of CFRP.construct an aircraft design tool that can takemulti-scale properties of materials into account4 / 15

Optimization Method Genetic Algorithm (GA)・ Algorithm that mimics the processof evolutionAdvantage・ Multi-objective optimizationis available・ A lot of solutions are obtainedwith one calculation.・ It is necessary to search a huge number of solutions.・ The calculation cost is generally high.・ Hard to combine with simulation.5 / 15

Optimization Method Response Surface Method・ A method to find an optimumsolution by using a response surfacewith few measurement data・ a Kriging response surface isconstructed from known samples.fˆ ( x ) r T R 1 ( f 1 )・ Using the EI value to find the nextsearch point with GA.EI : Expected ImprovementBy executing multi-objective optimizationon the response surface,It is possible to search Pareto solutionswith realistic execution time.6 / 15

Optimization Method Framework・ 2 simulation methods are used for objective function evaluationto construct the response surface.・ The next search points on the responsesurface are acquired by GA.・ The response surface is updated sequentially.7 / 15

Optimization Method CFD Q E F G 0 t x y zCalculate the pressuredistribution around thewing using finite volumemethod with the Eulerequationf aeroFrom the information of thepressure distribution, loaddistribution on the wing structure iscalculated using CVT methodf stStructural optimizationCarry out CFD and calculate the load on the structure8 / 15

Optimization Method Structural OptimizationStructural optimization using FEM and GA・ Application to composite materialswith the original evaluation function,any fracture criterion is available.Perform structural optimizationto obtain minimum weight.aiming to use multi-scale fracture criterionwhich can deal with the differencebetween resin type and fiber type in the optimization9 / 15

Application Optimization Target・90 passenger transonic jetdesign range 2700kmWhen applying new materials,how much can we lighten thestructure?Object 2ParetoFrontObject 1Pareto fronts between CFRP(T800s) andDuralumin(A7075) are compared10 / 15

Application Objective FunctionWeight Wst [kg]Range R [km](result of structural optimization)L V W0 R ln D c W1 Wst （Breguet range equation）RN WWiii 1N : Number of elementsFEM modelOptimumRange RMaximumStructural weight Wst minimumobjectiveFlight efficiencyLight weight11 / 15

Results Comparison between Pareto Fronts・ Weight-RangeOptimumRange [km]・ Pareto fronts showgood approximation bylinear interpolation・ From the comparisonof these interpolation lines,the gradient of CFRP is higherWeight [kg]・ The Pareto front of CFRP has the higher sensitivity of range to weight.・ Aircraft with a larger range have advantage of weight reduction,when applying CFRP12 / 15

Results Correlation Matrix of Duralumina: cross section area of rod elementt: thickness of shell elementRelationship betweenRange and Structural parameters(Duralumin)・ Longer range wing hasthicker skin on the upper skin.larger flange area on the lower wing.13 / 15

Results Correlation Matrix of CFRPa: cross section area of rod elementt: thickness of shell elementRelationship betweenRange and Structural parameters(CFRP)・ Longer range wing hasthicker skin on the front spar.larger flange area and thicker skin on the lower wing.14 / 15

ConclusionMethod- Aero-structural optimization toolby genetic algorithm using response surface method is constructed.-Aero-structural optimization capableof multiscale evaluation was constructed by usingoriginal evaluation function.-By performing optimization on duralumin and CFRP,Pareto Fronts was acquired and compared.Results- Aircraft with a larger range have advantage of weight reduction,when applying CFRP-Differences of structural design are confirmed.15 / 15

Thank you for your attention.16

Structural optimization using FEM and GA Optimization Method Structural Optimization Perform structural optimization to obtain minimum weight. ・Application to composite materials with the original evaluation function, any fracture criterion is available. aiming to use multi-scale fracture criterion which can deal with the difference