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Cost Optimization of Aircraft Structures
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures. (Lightweight 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.
Series
Trita-AVE, ISSN 1651-7660 ; 83
Keyword [en]
aircraft structures, optimization, cost estimation, manufacturing cost, direct operating cost, multiobjective optimization, multidisciplinary optimization, composites, airframe design
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-11482ISBN: 978-91-7415-500-6 (print)OAI: oai:DiVA.org:kth-11482DiVA: diva2:277152
Public defence
2009-12-11, D2, Lindstedtsvägen 5, KTH, 10044 Stockholm, 10:15 (English)
Opponent
Supervisors
Projects
European Framework Program 6, project ALCAS, AIP4-CT-2003-516092Nationella flygtekniska forskningsprogrammet (NFFP) 4, project kostnadseffektiv kompositstruktur (KEKS)
Note
QC 20100723Available from: 2009-11-19 Created: 2009-11-16 Last updated: 2012-01-27
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
3. Manufacturing process adaptation for integrated cost/weight optimisation of aircraft structures
Open this publication in new window or tab >>Manufacturing process adaptation for integrated cost/weight optimisation of aircraft structures
2009 (English)In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 38, no 2, 162-166(5) p.Article in journal (Refereed) Published
Abstract [en]

A methodology is developed that enables cost-efficient design of composite aircraft structures. In earlier work, a cost/weight optimisation framework was presented. This framework is here enhanced by a module that minimises the manufacturing cost in each iteration by adaptation of manufacturing parameters. The proposed framework is modular and applicable to a variety of parts and geometries. Commercially available software is used in all steps of theoptimisation. The framework extension is added to an existing cost/weight optimisation implementation and tested on an airliner centre wing box rear spar. Three optimisation runs are performed, and a low cost, an intermediate and a low weight design solution are found. The difference between the two extreme solutions is 4.4% in manufacturing cost and 9.7% in weight. Based on these optimisation trials, the effect of the introduced parameter adaptation module is analysed.

Place, publisher, year, edition, pages
Maney Publishing, 2009
Keyword
Cost/weight optimisation, Process adjustment, Parameter adaptation, Aircraft structures
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:kth:diva-11474 (URN)10.1179/174328909X387793 (DOI)000265404200019 ()2-s2.0-67649204253 (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
4. Cost/weight optimization of composite prepreg structures for best draping strategy
Open this publication in new window or tab >>Cost/weight optimization of composite prepreg structures for best draping strategy
2010 (English)In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 41, no 4, 464-472 p.Article in journal (Refereed) Published
Abstract [en]

The application of hand-laid carbon fiber prepreg is very expensive from a labor perspective. Therefore the manufacturing cost should be included in the design process. In this work, we propose a novel optimization framework which contains a draping simulation in combination with a detailed cost estimation package and the calculation of the structural performance based on FE. We suggest applying the methodology in two steps. First, a draping knowledge database is generated in which combinations of seed points and reference angles are evaluated in terms of fiber angle deviation, scrap, ultrasonic cuts and material shear. Second, a cost/weight optimization framework picks the best sets of plies during the subsequent optimization. The methodology is tested by means of a curved C-spar which is designed using plain weave and unidirectional prepreg. Different objectives in the generation of the draping database lead to different design solutions.

Place, publisher, year, edition, pages
Elsevier, 2010
Keyword
Cost/Weight Optimization, Finite element analysis, Prepreg, Lay-up (manual/automated)
National Category
Composite Science and Engineering
Research subject
SRA - Production
Identifiers
urn:nbn:se:kth:diva-11475 (URN)10.1016/j.compositesa.2009.11.012 (DOI)000275800400002 ()2-s2.0-75749103014 (Scopus ID)
Projects
European Framework Program 6, project ALCAS, AIP4-CT-2003-516092Nationella flygtekniska forskningsprogrammet (NFFP) 4, project kostnadseffektiv kompositstruktur (KEKS)
Funder
XPRES - Initiative for excellence in production research
Note

Uppdaterad från submitted till published: 20100723 QC 20100723

Available from: 2009-11-13 Created: 2009-11-13 Last updated: 2017-12-12Bibliographically approved
5. Material Selection for a Curved C-Spar Based on Cost Optimization
Open this publication in new window or tab >>Material Selection for a Curved C-Spar Based on Cost Optimization
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
Keyword
COST/WEIGHT OPTIMIZATION, COMPRESSIVE STRENGTH, AIRCRAFT STRUCTURES, FUSELAGE FRAMES, WEIGHT DESIGN, MINIMUM-COST, PERFORMANCE, COMPOSITES, PANELS, PART
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-39049 (URN)10.2514/1.C000188 (DOI)000291574700008 ()2-s2.0-79958017017 (Scopus ID)
Funder
TrenOp, Transport Research Environment with Novel Perspectives
Note

QC 20110907

Available from: 2011-09-07 Created: 2011-09-07 Last updated: 2017-12-08Bibliographically approved

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