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Material Selection for a Curved C-Spar Based on Cost Optimization
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.ORCID iD: 0000-0002-9744-4550
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.ORCID iD: 0000-0002-6616-2964
2011 (English)In: Journal of Aircraft, ISSN 0021-8669, E-ISSN 1533-3868, Vol. 48, no 3, 797-804 p.Article in journal (Refereed) Published
Abstract [en]

A case study for the cost optimization of aircraft structures based on the operating cost as an objective function is presented. The proposed optimization framework contains modules for estimation of the weight, manufacturing cost, nondestructive inspection cost, and structural performance; the latter is enhanced by a kinematic draping model that allows the fiber angles to be simulated more realistically. The case study includes five material systems: aircraft-grade aluminum, two types of resin-transfer molded noncrimp fabric reinforcements, and two types of M21/T800 prepreg. The results are compared in relation to each other, and it is shown that (depending on the estimated fuel burn share of the component) a different material system is favorable when optimizing for low-operating cost.

Place, publisher, year, edition, pages
American Institute of Aeronautics and Astronautics, 2011. Vol. 48, no 3, 797-804 p.
Keyword [en]
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-39049DOI: 10.2514/1.C000188ISI: 000291574700008ScopusID: 2-s2.0-79958017017OAI: diva2:439394
TrenOp, Transport Research Environment with Novel Perspectives

QC 20110907

Available from: 2011-09-07 Created: 2011-09-07 Last updated: 2015-09-29Bibliographically approved
In thesis
1. Cost Optimization of Aircraft Structures
Open this publication in new window or tab >>Cost Optimization of Aircraft Structures
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Composite structures can lower the weight of an airliner significantly. Due to the higher process complexity and the high material cost, however, the low weight often comes with a significant increase in production cost. The application of cost-effective design strategies is one mean to meet this challenge.

In this thesis, a simplified form of direct operating cost is suggested as a comparative value that in combination with multidisciplinary optimization enables the evaluation of a design solution in terms of cost and weight. The proposed cost optimization framework takes into account the manufacturing cost, the non-destructive testing cost and the lifetime fuel consumption based on the weight of the aircraft, thus using a simplified version of the direct operating cost as the objective function. The manufacturing cost can be estimated by means of different techniques. For the proposed optimization framework, feature-based parametric cost models prove to be most suitable.

Paper A 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.

Paper B proposes the inclusion of non-destructive testing cost in the design process of composite components, and the adjustment of the design strength of each laminate according to inspection parameters. Hence, the scan pitch of the ultrasonic testing is regarded as a variable, representing an index for the guaranteed material quality. It is shown that the cost for non-destructive testing can be lowered if the quality level of the laminate is assigned and adjusted in an early design stage.

In Paper C and Paper D the parameters of the manufacturing processes are upgraded during the cost optimization of the component. In Paper C, the framework is extended by the cost-efficient adaptation of parameters in order to reflect the situation when machining an aluminum component. For different weight penalties, the spar thickness and stringer geometry of the provided case study vary. In addition, another cutter is chosen with regard to the modified shape of the stringer. In Paper D, the methodology is extended to the draping of composite fabrics, thus optimizing not only the stacking layup, but also the draping strategy itself. As in the previous cases, the design alters for different settings of the weight penalty. In particular, one can see a distinct change in fiber layup between the minimum weight and the minimum cost solution.

Paper E summarizes the work proposed in Papers A-D and provides a case study on a C-spar component. Five material systems are used for this case study and compared in terms of cost and weight. The case study shows the impact of the weight penalty, the material cost and the labor rate on the choice of the material system. For low weight penalties, for example, the aluminum spar is the most cost-effective solution. For high weight penalties, the RTM system is favorable. The paper also discusses shortcomings with the presented methodology and thereby opens up for future method developments.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. xii, 53 p.
Trita-AVE, ISSN 1651-7660 ; 83
aircraft structures, optimization, cost estimation, manufacturing cost, direct operating cost, multiobjective optimization, multidisciplinary optimization, composites, airframe design
National Category
Vehicle Engineering
urn:nbn:se:kth:diva-11482 (URN)978-91-7415-500-6 (ISBN)
Public defence
2009-12-11, D2, Lindstedtsvägen 5, KTH, 10044 Stockholm, 10:15 (English)
European Framework Program 6, project ALCAS, AIP4-CT-2003-516092Nationella flygtekniska forskningsprogrammet (NFFP) 4, project kostnadseffektiv kompositstruktur (KEKS)
QC 20100723Available from: 2009-11-19 Created: 2009-11-16 Last updated: 2012-01-27

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