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Cost and weight effective composite design of automotive body structures
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.ORCID iD: 0000-0002-1224-3662
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The automotive industry stands in front of a great challenge, to decrease its impact on the environment. One important part in succeeding with this is to decrease the structural weight of the body structure and by that the fuel consumption or the required battery power. Carbon fibre composites are by many seen as the only real option when traditional engineering materials are running out of potential for further weight reduction. However, the automotive industry lacks experience working with structural composites and the methods for high volume composite manufacturing are immature. The development of a composite automotive body structure, therefore, needs methods to support and guide the conceptual work to improve the financial and technical results.

In this thesis a framework is presented which will provide guidelines for the conceptual phase of the development of an automotive body structure. The framework follows two main paths, one to strive for the ideal material diversity, which also defines an initial partition of the body structure based on the process and material selection. Secondly, a further analysis of the structures are made to evaluate if a more cost and weight efficient solution can be found by a more differential design and by that define the ideal part size.

In the case and parameter studies performed, different carbon fibre composite material systems and processes are compared and evaluated. The results show that high performance material system with continuous fibres becomes both

more cost and performance effective compared to industrialised discontinuous fibre composites. But also that cycle times, sometimes, are less important than a competitive feedstock cost for a manufacturing process. When further

analysing the manufacturing design of the structures it is seen that further partition(s) can become cost effective if the size and complexity is large enough.

 

 

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. , vii, 36 p.
Series
TRITA-AVE, ISSN 1651-7660 ; 2014:12
National Category
Vehicle Engineering
Research subject
Vehicle and Maritime Engineering
Identifiers
URN: urn:nbn:se:kth:diva-145292ISBN: 978-91-7595-151-5 (print)OAI: oai:DiVA.org:kth-145292DiVA: diva2:717380
Presentation
2014-06-04, Sal D3, Lindstedtsvägen 5, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency, 35854-1
Note

QC 20140527

Available from: 2014-05-27 Created: 2014-05-15 Last updated: 2014-05-27Bibliographically approved
List of papers
1. Method for cost and weight-efficient material diversity and partitioning of a carbon fibre composite body structure
Open this publication in new window or tab >>Method for cost and weight-efficient material diversity and partitioning of a carbon fibre composite body structure
2015 (English)In: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, ISSN 0954-4070, E-ISSN 2041-2991Article in journal (Refereed) Published
Abstract [en]

A method for the early concept phase is proposed, which is aimed at limiting the financial and performance-related riskswhen designing a carbon fibre composite automotive body structure. The method manages the structural requirementsimposed on the complete body structure and analyses the suitability of different carbon fibre material systems and pro-cesses. It also studies whether a high level of material diversity is desirable and the way in which to identify the optimalpartition of the body structure from a material system and manufacturing process selection point of view. Furthermore,since composite materials include both laminated materials and quasi-isotropic materials, an approach is presented thatenables the comparison of these materials variants during conceptual material selection. A case study exemplifies themethod and the results show that, in spite of the cost-sensitive nature of the automotive industry, utilization of the max-imum performance of these expensive composite materials is more important than efforts to achieve a rapid manufac-turing process.

Place, publisher, year, edition, pages
Sage Publications, 2015
Keyword
Concept phase, diversity of automotive material, body structure, material selection, process selection, structural composites
National Category
Composite Science and Engineering
Research subject
Vehicle and Maritime Engineering
Identifiers
urn:nbn:se:kth:diva-145713 (URN)10.1177/0954407015578037 (DOI)000367381700004 ()2-s2.0-84951936233 (Scopus ID)
Funder
XPRES - Initiative for excellence in production research
Note

QC 20150623

Available from: 2014-05-27 Created: 2014-05-27 Last updated: 2017-12-05Bibliographically approved
2. Integral versus differential design for high-volume manufacturing of composite structures
Open this publication in new window or tab >>Integral versus differential design for high-volume manufacturing of composite structures
2015 (English)In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 49, no 23, 2897-2908 p.Article in journal (Refereed) Published
Abstract [en]

In order to decrease the weight of the automotive body structure and increase the energy efficiency of future cars, attention is now turning towards structural composites, mainly carbon fibre-reinforced plastics. Composites have several advantages such as their excellent weight-specific properties and the possibility to be manufactured in large integral designs for a reduced weight and potentially lower cost. However, carbon fibre composites are expensive and for a cost sensitive industry such as the automotive industry, the challenge lies in creating a favourable business case with a well-balanced trade-off between weight and cost. A method is proposed to visualise the cost and weight advantages of either pursuing an integral design or a differential design, i.e. dividing the structure into a greater number of parts that are later assembled. The method focuses on the impact on cost and weight and considers structures with different part sizes and geometrical complexities. It is shown that, depending on the manufacturing process and series volume, larger and more complex parts may become more cost effective when divided into several, later-joined sub-parts. However, for smaller and/or less complex shapes, an integral design solution is always the best choice.

Place, publisher, year, edition, pages
Sage Publications, 2015
Keyword
Composites, automotive, manufacturing, partition, design
National Category
Composite Science and Engineering
Research subject
Vehicle and Maritime Engineering
Identifiers
urn:nbn:se:kth:diva-145714 (URN)10.1177/0021998314557684 (DOI)000360851800007 ()2-s2.0-84941136175 (Scopus ID)
Funder
XPRES - Initiative for excellence in production research
Note

QC 20150004

Available from: 2014-05-27 Created: 2014-05-27 Last updated: 2017-12-05Bibliographically approved

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