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Technical cost modelling and efficient design of lightweight composites in structural applications
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.ORCID iD: 0000-0001-6729-8604
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A lightweight transport design reduces fuel costs and emissions and can be achieved through the use of fibre-reinforced composite materials. Although lightweight, the composite raw material can be expensive and the sequential component production challenging and costly. To design weight- and cost-efficient composite structures and find ways to reduce production costs, technical cost modelling must be applied. In this thesis, a technical cost model for composite manufacture, assembly and basic inspection is proposed and implemented to identify cost drivers, evaluate trending design strategies and suggest appropriate composite design guidelines for transport and aeronautical applications. 

Among identified cost drivers, material costs dominates at 50-90 % of the total part cost also for low annual volumes. Tooling costs are second in importance for slow processes and large parts while the importance of investment and labour depends on degree of automation. Part integration is shown to only marginally reduce cost. Traditional composite assembly is in turn found to potentially reduce costs by 30 % through the elimination of non-value-adding processes such as shimming and part positioning. In comparison to part integration, sandwich design exhibits superior cost- and weight-efficiency for low-to-intermediate stiffness levels. Moreover, the industry impact of a sustainable, circular recycling flow of composite materials is estimated and shown to give up to halved raw material costs as well as cost returns also for virgin carbon fibre users. Low-cost fibres such as glass, lignin-based carbon, hemp and recycled carbon fibres are found to be highly cost-competitive also for structural adaptions.

The technical cost model, method and results presented in this thesis provide important composite design conclusions and a foundation for further modelling work needed to reach that elusive weight- and cost-optimal composite design.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. , p. 62
Series
TRITA-SCI-FOU ; 2019:9
Keywords [en]
Technical cost modelling; composite materials; carbon fibre; lightweight design; optimization
National Category
Vehicle Engineering Composite Science and Engineering
Research subject
Vehicle and Maritime Engineering
Identifiers
URN: urn:nbn:se:kth:diva-244386ISBN: 978-91-7873-104-6 (print)OAI: oai:DiVA.org:kth-244386DiVA, id: diva2:1290210
Public defence
2019-03-14, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Funder
EU, FP7, Seventh Framework Programme, 314003XPRES - Initiative for excellence in production research
Note

QC 20190220

Available from: 2019-02-20 Created: 2019-02-20 Last updated: 2019-02-20Bibliographically approved
List of papers
1. A composite cost model for the aeronautical industry: Methodology and case study
Open this publication in new window or tab >>A composite cost model for the aeronautical industry: Methodology and case study
2015 (English)In: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 79, p. 254-261Article in journal (Refereed) Published
Abstract [en]

This paper presents a novel composite production cost estimation model. The strength of the model is its modular construction, allowing for easy implementation of different production methods and case studies. The cost model is exemplified by evaluating the costs of a generic aeronautical wing, consisting of skin, stiffeners and rib feet. Several common aeronautical manufacturing methods are studied. For studied structure, hand layup is the most cost-effective method for annual volumes of less than 150 structures per year. For higher production volumes automatic tape layup (All) followed by hot drape forming (HDF) is the most cost-effective choice.

Keywords
Carbon fibre, Analytical modelling, Lay-up (manual/automated), Prepreg
National Category
Materials Engineering Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-173130 (URN)10.1016/j.compositesb.2015.04.043 (DOI)000358808300028 ()2-s2.0-84929324806 (Scopus ID)
Funder
EU, FP7, Seventh Framework Programme, 314003XPRES - Initiative for excellence in production research
Note

QC 20150918

Available from: 2015-09-18 Created: 2015-09-07 Last updated: 2019-02-20Bibliographically approved
2. Cost efficiency, integration and assembly of a generic composite aeronautical wing box
Open this publication in new window or tab >>Cost efficiency, integration and assembly of a generic composite aeronautical wing box
2016 (English)In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 152, p. 1014-1023Article in journal (Refereed) Published
Abstract [en]

This paper presents a cost-efficiency study of part integration with respect to reduced assembly effort within aeronautical composite structures. The study is performed through the use, and continuous improvement upon, a previously developed cost model. Focus are on the assembly and basic inspection a wing box, part of a section of a full wing, where involved parts are all considered to be manufactured from carbon fibre reinforced plastic (CFRP). Treated cases range from traditional, mechanical joining, to high integration either through co-curing or co-bonding of composite structures. The outcome of presented cost study shows that increased integration decreases the overall production cost of said considered wing box. In general it is shown that co-curing or co-bonding reduces a number of cost-expensive assembly steps in comparison to mechanical joining.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Cost estimation, Assembly, Inspection, Co-curing, Co-bonding, Mechanical joining
National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:kth:diva-192708 (URN)10.1016/j.compstruct.2016.06.032 (DOI)000381647500090 ()2-s2.0-84978033586 (Scopus ID)
Note

QC 20160926

Available from: 2016-09-26 Created: 2016-09-20 Last updated: 2019-02-20Bibliographically approved
3. The economic and mechanical potential of closed loop material usage and recycling of fibre-reinforced composite materials
Open this publication in new window or tab >>The economic and mechanical potential of closed loop material usage and recycling of fibre-reinforced composite materials
(English)Manuscript (preprint) (Other academic)
Abstract [en]

This paper presents a novel recyclate value model derived from the retained mechanical performance of retrieved fibres in fibre-reinforced composites. The proposed recyclate value model was used to perform an economic analysis for establishing the future closed-loop material usage of fibre-reinforced composite materials. State-of-the-art recycling of carbon and glass-reinforced thermosets was adopted and resulted in a proposed recycling hierarchy in order to achieve a more sustainable environment and raw material cost reduction. The recyclate value model showed that approximately 50% material cost reductions can be achieved at comparable mechanical performance by using recycled fibre instead of virgin fibre in appropriate applications. From the aspect of lightweight design this cost reduction provides the designer with new material choices, appropriate for lower cost and diverse stiffness designs. The proposed closed-loop hierarchy documents the importance of further improvement of fibrous material recycling, including sorting according to mechanical performance, in order to identify application areas previously not utilised and to maximise material sustainability and value throughout the material's lifetime.

Keywords
recycled carbon fibres; recycled glass fibres; circular economy; economy
National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:kth:diva-244383 (URN)
Funder
XPRES - Initiative for excellence in production research
Note

QC 20190220

Available from: 2019-02-20 Created: 2019-02-20 Last updated: 2019-02-20Bibliographically approved
4. From aviation to automotive - a study on material selection and its implication on cost and weight efficient structural composite and sandwich designs
Open this publication in new window or tab >>From aviation to automotive - a study on material selection and its implication on cost and weight efficient structural composite and sandwich designs
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The structural design of composite materials is often challenging as its driven by a trade-off between lightweight structural performance and production costs. Addressing this design trade-off, this paper presents a methodology and case study that compares the weight- and production cost-potential of different composite materials and structural designs solutions through the use of a proposed application-bound design cost. Representative design solutions; monolithic, u-beam-, sandwich-insert- and sandwich-stiffened, are each optimized with respect to bending and torsional stiffness of increased severity to chart an extrapolated application map with respect to cost and stiffness. Optimized sandwich designs are shown to have lowest design cost where full stiffness is achieved. Alternative fibre materials researched; glass fibre, recycled carbon fibre, lignin-based fibres and hemp fibres, all reduce costs but at compromised stiffness. Ultimately, the case study demonstrates the impact of early design and material selection and justifies introducing novel fibre systems to reduce design cost.

Keywords
Carbon fibres; Sandwich structures; Natural fibres; Recycled carbon fibres
National Category
Vehicle Engineering Composite Science and Engineering
Identifiers
urn:nbn:se:kth:diva-244384 (URN)
Funder
XPRES - Initiative for excellence in production research
Note

QC 20190220

Available from: 2019-02-20 Created: 2019-02-20 Last updated: 2019-02-20Bibliographically approved

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Karlsson Hagnell, Mathilda

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