A CAD/CAE based multidisciplinary process

for aircraft structure design BackgroundAerospace structures are complex systems and the components are highly interrelated with each other. The design process is multidisciplinary in nature, involving several design aspects, such as manufacturing cost, weight and structural integrity. Multidisciplinary design and optimization (MDO) will be used to find the well compromised design for a complex system during the conceptual design phase. Knowledge based engineering (KBE) is an technique for implementing MDO while the design and engineering engine (DEE) is a set of advance software tools which support and accelerate the design process of a complex product through elimination of non-repetitive activities. The paradigm of the DEE is shown in Figure 1.

PublicationsWang, H. and van Tooren, M.J.L., “Knowledge Based Engineering Platform for Multidisciplinary Fuselage Design and Analysis,” Proceedings of 2010 Asia-Pacific International Symposium on Aerospace and Technology[CD-ROM], Chinese Society of Aeronautics and Astronautics, Xi’an, China, Sept. 2010.Wang, H. and van Tooren, M.J.L., “Bi-level Fuselage Structural Design in a Knowledge Based Engineering Environment”, Proceedings of Eurogen 2011 Conference, Capua, Italy, Sept. 2011.Zhao, X., Wang, H., Curran, R. and van Tooren, M.J.L., “Concurrent Aerospace Thermoplastic Stiffened Panel Conceptual Design and Cost Estimation using Knowledge Based Engineering”, Proceedings of 19th ISPE International Conference on Concurrent Engineering, Trier, Germany, Sept. 2012.Wang, H., Zhao, X., Curran, R. and van Tooren, M.J.L., “Parametric Modeling of Fuselage Panels for Structural Analysis and Cost Estimation”, Proceedings of 3rd Aircraft Structural Design Conference, Delft, the Netherlands, Oct. 2012.van Dijk, R., Zhao, X. , Wang, H., and van Dalen, F., “Multidisciplinary Design and Optimisation of Aircraft Box Structures”, Proceedings of 3rd Aircraft Structural Design Conference, Delft, the Netherlands, Oct. 2012.

PhD Candidate: Haiqiang WangDepartment: AWEPSection: Flight Performance and PropulsionSupervisor: G. La RoccaPromoter: M.J.L. van ToorenStart date: 1-9-2009Funding: Chinese Scholarship CouncilCooperations: Fokker Aerostructures

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Figure 6: Example CAD models of the wing-like structures which the DEE is able to generate.

Figure 4: Comparison with the predicted and actual fuselage weight of the considered aircrafts.

Figure 3: An application case for predicting fuselage weight of Prandtl plane, an unconventional configuration.

Fuselage DEE: a physics-based weight prediction tool setTraditionally aircraft fuselage weight is estimated based on the statistical weight data from previous projects. The method could not be used for unconventional configurations. In addition, the method is difficult to quantify the weight saving due to different material systems and structural layouts. A set of tools are developed for fuselage: a parametric fuselage model generating the outer mould line and cabin arrangement and Patran session files for automating FE model generation process; a global FE model for generating running loads for panel skin elements under typical flight, grounding and landing load cases according CAR 25; a local stiffened panel sizing module determining the panel dimensions with the giving loads from global FE model.

Wing like structure DEE: a tool set for cost and weight trade-off study Cost and weight are sometimes contradicting objectives for aerospace structure design. It is challenging for designers to try more designs in order to find the well balanced design. A set of tools is developed to investigate the cost and weight variations due to different structure layouts, material systems and manufacturing techniques. The tool set is comprised by the following components: the wing-like structure parametric model generating the CAD model of the outer module lines and internal structures, Patran session files for automating the generating process of FE model, and inputs for cost analysis; a global FE model to calculate the running loads for the plate; a local composite plate sizing model determining the ply numbers under each ply orientation; a bottom-up parametric cost estimation module to estimate manufacturing cost.

Figure 2: Validation cases for conventional configuration aircraft: A330B2, A320-200, Fokker100, B737-200,ATR42.

Conclusions and recommendationsThe fuselage and wing-like DEE have been successfully developed to support the MDO study of aerospace structure. The MMG is the core of the DEEs, generating the CAD models and preparing the inputs for FEA software and cost analysis tools. A large range of fuselage and wing-like structures can be modelled by the DEEs, as shown in Figure 2,3,6. The product knowledge and process knowledge are captured and restored, and can be reused for future projects. Compared with the several days the traditional design method takes, the DEEs is able to converge within several hours. Integrated with more realistic analysis tools from industry, the DEEs could be able to find the optimum design.

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Figure 5: Weight tendency under different combinations of frame pitch and panel efficiency.

Figure 1: The DEE and its components

Figure 7: A design case for G650 rudder: what if a rib is added or removed

Design Weight [kg] Cost ($)

Baseline 60.2 35840

Baseline - 1 rib 60.4 35664

Baseline + 1 rib 58.6 35680