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Cost/Weight Optimization of Aircraft Structures
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Composite structures can lower the weight of an airliner significantly. The increased production cost, however, requires the application of cost-effective design strategies. Hence, a comparative value is required which is used for the evaluation of a design solution in terms of cost and weight. The direct operating cost (DOC) can be used as this comparative value; it captures all costs that arise when the aircraft is flown. In this work, a cost/weight optimization framework for composite structures is proposed. It takes into account manufacturing cost, non-destructive testing cost and the lifetime fuel consumption based on the weight of the aircraft, thus using a simplified version of the DOC as the objective function.

First, the different phases in the design of an aircraft are explained. It is then focused on the advantages and drawbacks of composite structures, the design constraints and allowables, and non-destructive inspection. Further, the topics of multiobjective optimization and the combined optimization of cost and weight are addressed. Manufacturing cost can be estimated by means of different techniques; here, feature-based cost estimations and parametric cost estimations proved to be most suitable for the proposed framework. Finally, a short summary of the appended papers is given.

The first paper contains a parametric study in which a skin/stringer panel is optimized for a series of cost/weight ratios (weight penalties) and material configurations. The weight penalty, defined as the specific lifetime fuel burn, is dependent on the fuel consumption of the aircraft, the fuel price and the viewpoint of the optimizer. It is concluded that the ideal choice of the design solution is neither low-cost nor low-weight but rather a combination thereof.

The second paper proposes the inclusion of non-destructive testing cost in the design process of the component, and the adjustment of the design strength of each laminate according to the inspection parameters. Hence, the scan pitch of the ultrasonic testing is regarded as a variable, representing an index for the (guaranteed) laminate quality. It is shown that the direct operating cost can be lowered when the quality level of the laminate is assigned and adjusted in an early design stage.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , ix, 45 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2008-08
Keyword [en]
Cost/Weight Optimization, Weight Penalty, Direct Operating Cost, Composite Structures, Non-destructive testing, Finite element analysis (FEA)
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-4645ISBN: 978-91-7178-888-7 (print)OAI: oai:DiVA.org:kth-4645DiVA: diva2:13224
Presentation
2008-04-30, D3, KTH, Lindstedtsvägen 5, Stockholm, 13:00
Opponent
Supervisors
Note
QC 20101112Available from: 2008-04-22 Created: 2008-04-22 Last updated: 2010-11-12Bibliographically approved
List of papers
1. Integrated cost/weight optimization of composite skin/stringer elements
Open this publication in new window or tab >>Integrated cost/weight optimization of composite skin/stringer elements
2007 (English)In: Proceedings of the 16th International Conference on Composite Materials, Springer, 2007, 325-334 p.Conference paper, Published paper (Refereed)
Abstract [en]

In this paper, a methodology for a combined cost/weight optimization of composite elements is proposed. The methodology is similar to the work of Curran et al. [1], where the objective function is formed by manufacturing costs and a so-called weight penalty. This weight penalty could include the effect of fuel burn, environmental impact or con-tractual penalties due to overweight, and depends on the view of the "optimizer". In our approach, the analytical cost model is replaced by a commercial software package that allows a more realistic model of the manufacturing costs. In the spotlight is a parameter study, in which the weight penalty is varied from zero to infinity, literally varying from pure cost to pure weight opti-mization. This is done for three material configura-tions: a metal/metal, a composite/metal and a com-posite/composite skin/stringer panel. It is shown that the design solution depends on the magnitude of the weight penalty and that - depending on this magni-tude - another material configuration has to be re-garded as the optimum.

Place, publisher, year, edition, pages
Springer, 2007
Keyword
Cost/Weight Optimization, Weight Penalty, Direct Operating Cost, Composite Structures
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-8015 (URN)2-s2.0-79960055319 (Scopus ID)978-493113605-2 (ISBN)
Conference
16th International Conference on Composite Materials, ICCM-16 - "A Giant Step Towards Environmental Awareness: From Green Composites to Aerospace", Kyoto, Japan, 8 July 2007 through 13 July 2007
Note

QC 20101112

Available from: 2008-04-22 Created: 2008-04-22 Last updated: 2015-07-09Bibliographically approved
2. Cost optimization of composite aircraft structures including variable laminate qualities
Open this publication in new window or tab >>Cost optimization of composite aircraft structures including variable laminate qualities
2008 (English)In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 68, no 13, 2748-2754 p.Article in journal (Refereed) Published
Abstract [en]

Composite structures can lower the weight of an airliner significantly. The increased production cost, however, requires the application of cost-effective design strategies in which cost, weight and the desired laminate quality are taken into account. This paper proposes an optimization framework for composite aircraft structures that minimizes the direct operating cost on a part level. In addition to previous models, a non-destructive testing model is implemented that calculates design allowables of a laminate based on ultrasonic scan parameters. In a case study, the effect of the laminate quality on the direct operating cost is discussed. It is investigated how the permissible flaw size and therefore the scan pitch of a composite laminate can influence the optimal solution in terms of cost and weight; thus, the manufacturing cost, the non-destructive testing cost and the weight of a component can be balanced by optimizing the laminate quality in an early design phase.

Place, publisher, year, edition, pages
Elsevier, 2008
Keyword
Structural Composites, Non-destructive testing, Strength, Finite element analysis (FEA), Optimization
National Category
Production Engineering, Human Work Science and Ergonomics
Identifiers
urn:nbn:se:kth:diva-11473 (URN)10.1016/j.compscitech.2008.05.024 (DOI)000261388200021 ()2-s2.0-52749085412 (Scopus ID)
Projects
European Framework Program 6, project ALCAS, AIP4-CT-2003-516092Nationella flygtekniska forskningsprogrammet (NFFP) 4, project kostnadseffektiv kompositstruktur (KEKS)
Note

QC 20100723

Available from: 2009-11-13 Created: 2009-11-13 Last updated: 2017-12-12Bibliographically approved

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