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Processing of self-reinforced poly(ethylene terephthalate) composites for automotive applications
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.ORCID iD: 0000-0001-9909-7620
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The vehicles of the future must have less negative environmental impact during their use phase than the vehicles of today in order to avoid major climate change on earth. Consequently electric vehicles are currently under development with the purpose of reducing CO2 emissions when the vehicle is

driven. There are also efforts put in to reducing the weight of vehicles in order to reduce the demand for energy to drive them. One important aspect of weight reduction is that new materials and technologies are developed. Plastic materials have low a density and can therefore be used to reduce the weight of vehicle components and with composite materials there is further potential for weight reduction. Self-reinforced thermoplastic composite materials are materials in which both reinforcement and matrix are thermoplastic materials and thanks to their low density and relatively good mechanical properties, these materials may be used for weight reduction of vehicle components.

 

The aim of this thesis is to study selected process parameters for component manufacturing with self-reinforced poly(ethylene terephthalate) (SrPET) in order to increase knowledge and thereby advance the field of self-reinforced PET composites. This thesis shows that stretching the material in the manufacturing process increases the mechanical performance of the material due to increased orientation of the amorphous phase in the PET reinforcement. However, stretching introduces stresses in the material that give rise to negative shape distortions in the formed component. The degree of stretching during forming must therefore be controlled in order to achieve a robust serial production. The concept of a SrPET component over-moulded for integration of stiffeners and attachments has been evaluated in a life-cycle-assessment. This evaluation shows that the component weight can be reduced compared to technology currently in use and thereby contribute to increased sustainability of transport.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017.
Series
TRITA-AVE, ISSN 1651-7660 ; 2017:94
National Category
Composite Science and Engineering
Research subject
Vehicle and Maritime Engineering
Identifiers
URN: urn:nbn:se:kth:diva-219926ISBN: 978-91-7729-651-5 (print)OAI: oai:DiVA.org:kth-219926DiVA, id: diva2:1166082
Public defence
2018-01-26, Kollegiesalen, Brinellvägen 8, Stockholm, 09:00 (English)
Opponent
Supervisors
Note

QC 20171215

Available from: 2017-12-15 Created: 2017-12-14 Last updated: 2017-12-15Bibliographically approved
List of papers
1. Influence of fibre stretching on the microstructure of self-reinforced poly(ethylene terephthalate) composite
Open this publication in new window or tab >>Influence of fibre stretching on the microstructure of self-reinforced poly(ethylene terephthalate) composite
2016 (English)In: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 35, no 21, p. 1634-1641Article in journal (Refereed) Published
Abstract [en]

Self-reinforced poly(ethylene terephthalate) laminates were prepared from woven fabric by compression moulding. The fabric was stretched to different degrees during heating before hot consolidation to simulate a manufacturing process where the material is stretched through forming. High tenacity poly(ethylene terephthalate) fibres with different degrees of stretching were prepared for a comparison to laminates. Tensile tests were made to characterize mechanical properties, while dynamical mechanical analysis, differential scanning calorimetry, FTIR spectroscopy and X-ray diffraction analysis were employed to study microstructural changes caused by the stretching. Tensile tests show that 13% stretching of the fabric increases the laminate tensile stiffness by 34%. However, same degree of stretching for pure fibres increases the fibre tensile stiffness by 111%. Crystallinity and molecular conformations are not influenced by stretching while shrinkage upon heating increases with degree of stretching. Shrinkage is known to be related to disorientation of non-crystalline regions whereof the conclusion from this study is that the increased tensile properties are due to orientation of the non-crystalline regions of the fibre.

Keyword
Self-reinforced polymer composite, poly(ethylene terephthalate), microstructural analysis, mechanical properties
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-196978 (URN)10.1177/0731684416662328 (DOI)000386959000003 ()2-s2.0-84994092870 (Scopus ID)
Note

QC 20161213

Available from: 2016-12-13 Created: 2016-11-28 Last updated: 2017-12-14Bibliographically approved
2. Influence of fibre shrinkage and stretching on the mechanical properties of self-reinforced poly(ethylene terephthalate) composite
Open this publication in new window or tab >>Influence of fibre shrinkage and stretching on the mechanical properties of self-reinforced poly(ethylene terephthalate) composite
2014 (English)In: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 33, no 17, p. 1644-1655Article in journal (Refereed) Published
Abstract [en]

Self-reinforced poly(ethylene terephthalate) composite laminates were manufactured from fabric using a hot press. Fabric was either allowed to shrink or exposed to stretching during different phases of the manufacturing process. Composite macrostructure, crimp, was investigated and results showed that shrinkage affects fibre crimp more than stretching does. Mechanical tests showed that shrinkage do not significantly affect mechanical properties while stretching fabric by 10% during heating results in 50% increase in tensile stiffness. The lack of correlation between crimp and mechanical properties indicates that mechanical properties for self-reinforced poly(ethylene terephthalate) composites are dominated by their microstructure, molecular orientation, which may be affected by the manufacturing process.

Keyword
Self-reinforced composite, poly(ethylene terephthalate), mechanical properties, processing, macrostructure
National Category
Polymer Technologies Materials Engineering
Identifiers
urn:nbn:se:kth:diva-151329 (URN)10.1177/0731684414541018 (DOI)000340939600008 ()2-s2.0-84906667850 (Scopus ID)
Funder
XPRES - Initiative for excellence in production research
Note

QC 20140918

Available from: 2014-09-18 Created: 2014-09-18 Last updated: 2017-12-14Bibliographically approved
3. Environmental performance of self-reinforced composites in automotive applications - Case study on a heavy truck component
Open this publication in new window or tab >>Environmental performance of self-reinforced composites in automotive applications - Case study on a heavy truck component
2016 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 103, p. 321-329Article in journal (Refereed) Published
Abstract [en]

A screening environmental life cycle analysis (LCA) of the novel self-reinforced poly(ethylene therephthalate) (SrPET) is presented in this paper. A truck exterior panel is used as case study where a concept design made by SrPET is assessed and compared to a glass fibre reinforced composite and a thermoplastic blend that are currently used for the selected component. The results showed that the SrPET panel has 25% lower environmental impact compared to the current design, with no significant life cycle trade-offs. SrPET offers possibilities for weight reduction while maintaining good mechanical properties. As the impact during use phase is expected to decrease in the future the relative importance of manufacturing and end-of-life (EOL) will increase. Thus SrPET can be considered a competitive material for replacing existing energy intense non-recyclable composites.

Place, publisher, year, edition, pages
Elsevier, 2016
Keyword
Self-reinforced composites, Environmental impact, Automotive component, Life cycle assessment
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-189067 (URN)10.1016/j.matdes.2016.04.090 (DOI)000376892300037 ()2-s2.0-84966335400 (Scopus ID)
Note

QC 20160628

Available from: 2016-06-28 Created: 2016-06-27 Last updated: 2017-12-14Bibliographically approved

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