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Cost/weight optimization of composite prepreg structures for best draping strategy
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
2010 (English)In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, 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. Vol. 41, no 4, 464-472 p.
Keyword [en]
Cost/Weight Optimization, Finite element analysis, Prepreg, Lay-up (manual/automated)
National Category
Composite Science and Engineering
Research subject
SRA - Production
URN: urn:nbn:se:kth:diva-11475DOI: 10.1016/j.compositesa.2009.11.012ISI: 000275800400002ScopusID: 2-s2.0-75749103014OAI: diva2:277045
European Framework Program 6, project ALCAS, AIP4-CT-2003-516092Nationella flygtekniska forskningsprogrammet (NFFP) 4, project kostnadseffektiv kompositstruktur (KEKS)
XPRES - Initiative for excellence in production research

Uppdaterad från submitted till published: 20100723 QC 20100723

Available from: 2009-11-13 Created: 2009-11-13 Last updated: 2015-09-22Bibliographically 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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