Development of thermoplastic biocomposites based on aligned hybrid yarns for fast composite ...

134 Pages·2015·9.66 MB·English

by  Behnaz Baghaei

Thesis for the Degree of Doctor of Philosophy

Development of thermoplastic biocomposites
based on aligned hybrid yarns for fast composite
manufacturing

Behnaz Baghaei
Copyright©Behnaz Baghaei
Swedish Centre for Resource Recovery
University of Borås
SE-501 90 Borås, Sweden

Digital version: http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-764
ISBN 978-91-87525-79-7 (printed)
ISBN 978-91-87525-80-3 (pdf)

ISSN 0280-381X Skrifter från Högskolan i Borås, nr. 74

Cover Photo: Masoud Salehi
Printed in Sweden by Responstryck AB
Borås 2015
Abstract
The interest in natural fibres as reinforcement for composite materials has been steadily increasing
due to their attractive mechanical properties and the possibility of making more eco-friendly
materials. Currently, various alternatives are being introduced for commercial applications, as fibres
such as hemp, jute and flax exhibit properties, which make them appropriate for structural
composite components. Biocomposites offer reductions in weight and cost and have less reliance on
foreign oil resources, making them attractive. Several investigations have revealed that the full
utilisation of fibre mechanical properties in the final composites can be exploited, provided an
aligned fibre orientation is chosen. In fact, a major challenge for natural fibre reinforced composites
is to achieve high mechanical performance at competitive prices. The use of commingled/hybrid
yarns is one of the more promising methods for manufacturing structural thermoplastic composites.

Commingled yarns of thermoplastic and reinforcing fibres offer a potential for cost-effective
production of composite parts, thanks to reduced applied pressures and impregnation times during
processing. Besides economic advantages, there is also direct control over fibre placements and ease
of handling of fibres in yarn process. The yarn technologies provide homogenous distribution of
reinforcing fibre and matrix. Variation in natural fibre properties has been a major problem facing
composite manufacturers, compared to carbon and glass fibres that have well-defined production
processes. This issue can be addressed by regenerated cellulose fibres. These fibres can be
reproduced easily with high surface evenness and even quality, making it possible to get consistent
results, which is not possible with natural fibres. Combination of natural and regenerated cellulose
fibre brings together the best of both materials. The end result is a product with superior properties,
which could not be obtained by the individual components.

This thesis describes the development of aligned hybrid yarns with low fibre twist, for high
performance natural (hemp) and man-made (Lyocell) cellulose fibre-reinforced biocomposites,
suitable for use in structural or semi-structural applications. The properties of composites in terms
of fibre orientation, off-axis angle and alkali treatment were investigated, focusing on determining
void%, water absorption, mechanical and thermo-mechanical properties. The results show that
combining hemp and Lyocell in PLA composite leads to the reduction of moisture absorption and
can improve the mechanical properties. The mechanical properties of the composites were highly
affected by the fibre direction. The alkali treatment on hemp fibre improved the mechanical
properties of the composites.

Keywords: Hybrid yarns, Mechanical properties, Porosity, Weaving, Alkali treatment, Compression
moulding

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II
List of Publications
This thesis is based on the results presented in the following publications:

I. Baghaei B, Skrifvars M and Berglin L. (2013) Manufacture and characterization of
thermoplastic composites made from PLA/hemp co-wrapped hybrid yarn prepregs. Composites
Part A: Applied Science and Manufacturing 50:93-101.
II. Baghaei B, Skrifvars M, Salehi M, Bashir T, Rissanen M and Nousiainen P. (2014) Novel
aligned hemp fibre reinforcement for structural biocomposites: Porosity, water absorption,
mechanical performances and viscoelastic behaviour. Composites Part A: Applied Science and
Manufacturing 61:1-12.
III. Baghaei B, Skrifvars M, Berglin L. (2015) Characterization of thermoplastic natural fibre
composites made from woven hybrid yarn prepregs with different weave pattern. Composites
Part A: Applied Science and Manufacturing 76:154-161.
IV. Baghaei B, M. Skrifvars, Rissanen M and Ramamoorthy SK. (2014): Mechanical and thermal
characterization of compression moulded polylactic acid natural fiber composites reinforced by
hemp and Lyocell fibers. Journal of Applied Polymer Science, 131(15) DOI:10.1002/app.40534.
V. Baghaei B, M. Skrifvars. Characterisation of polylactic acid biocomposites made from prepregs
composed of woven polylactic acid/hemp-Lyocell hybrid yarn fabrics. Submitted to Composites
Part A: Applied Science and Manufacturing

Statement of Contribution
The author of this thesis, Behnaz Baghaei, was main author of all the publications and performed
most of the experimental work, data analysis and manuscript writing in all publications. Dr Lena
Berglin prepared the textile fabrics for Publications III and V. Dr Marja Rissanen performed the
tensile testing of the fibres for Publications II and IV. Other co-authors assisted with data analysis
and manuscript writing.
SEM analysis was performed at Swerea IVF (Sweden) for Publication I and Chalmers University of
Technology (Sweden) for Publications II, III, IV and V.
Permission from publishers
Permission was obtained from:
- ELSEVIER to include Publications I, II and III in the printed version of this thesis
- John Wiley and Sons to include Publication IV in the printed version of this thesis

III
Conference Contributions
1. Baghaei B and Skrifvars M. Investigation of pattern style of woven fabrics produced from
hybrid wrap spun yarns on fabricated composite, 20th International Conference on
Composite Materials in Copenhagen, Denmark, July 19-24, 2015 (oral presentation)
2. Baghaei B, Skrifvars M and Salehi M. Aligned hemp yarn reinforced biocomposites:
porosity, water absorption, thermal and mechanical properties, 16th European conference on
composite materials, Seville, Spain, June 22-26, 2014 (oral presentation)
3. Baghaei B, Skrifvars M and Berglin L. Tailoring of the mechanical and thermal properties
of hemp/PLA hybrid yarn composites, 3rd Avancell conference, Göteborg, Sweden, October
8-9, 2013 (Poster)
4. Baghaei B, Skrifvars M and Berglin L. Tailoring of the mechanical and thermal properties
of hemp/PLA hybrid yarn composites, IPLA Global Forum on Sustainable Waste
Management for the 21st Century Cities, Borås, Sweden, September 9-11, 2013 (Poster)
5. Baghaei B, Skrifvars M and Berglin L and Ramamoorthy SK. Hemp/PLA co-wrapped
hybrid yarns for structured thermoplastic composites, 50th Anniversary Nordic Polymer
Days, Helsinki, Finland, May 28-31, 2013 (oral presentation)

IV
Acknowledgements
I would like to thank everyone who has contributed immensely to my life in many remarkable ways.
First and foremost, I would like to express my deepest gratitude to my supervisor, Professor Mikael
Skrifvars, for his support during these past four years. I appreciate all his contributions of time, idea,
scientific advice and immense knowledge.
Besides my supervisor, I would like to thank my co-supervisors, Dr Lena Berglin and Dr Dan
Åkesson, for their insightful comments and encouragement.
I also wish to extend my gratitude to my examiner, Professor Tobias Richards, for making it
possible for me to present this dissertation.
Professor Mohammad Taherzadeh, I am so grateful for your valuable guidance.
The members of polymer group have contributed immensely to my personal and professional time
at Borås. The group has been a source of friendship as well as good advice and collaboration. To my
friends: Tariq, Fatimat, Haike, Sunil, Adib, I say thank you.
I would like to thank Dr Peter Therning, Tomas Wahnström, Sari Sarhamo, Susanne Borg, Louise
Holmgren and Thomas Södergren for your support throughout my studies.
I am also very grateful to my teachers, Dr.Magnus Lundin, Dr Kim Bolton and Dr Anita Pettersson.
I extend my gratitude to all PhD students and colleagues at the Swedish Centre of Resource
Recovery for being such wonderful friends and creating a pleasant working environment.
In addition, I thank my wonderful friends Khatereh, Abas, Narges, Ehsan, Noushin, Mahdi, Mehran,
Zohreh, Khosrow, Parvin, Nima, Shahram, Mehrsa, Johan, Kamran, Solmaz, Maryam, Gergely,
Marjan, Farhang, Samira, Farzad, Negar, Arman, Davood, Mina, Masoud, Faranak, Amin, Sima,
Raj, Rouzbeh and Sahar.
To my husband, Masoud, I express my deepest gratitude. You have always been there cheering me
up and standing by my side through the good times and bad. I would also like to thank my dear
parents, brother (Amirali), sister (Bahareh) and brother-in-law (Majid). They have always supported
me and encouraged me with their best wishes. I am thankful for all support from my parents-in-law.
I express my gratitude to Patrik Johansson and Joachim Almvång from Engtex Company for
making the fabrics for this project.
Finally, I would like to thank other institutions that were part of my research, either helping me with
instruments or providing support: Swerea AB, Sweden; Chalmers University, Sweden and Tampere
University of Technology, Finland.
This work was financed by Ångpanneföreningens (Åforsk) and Smart Textiles (University of Borås)
and their contributions are greatly acknowledged.

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Abbreviations
NMMO N-Methylmorpholine N-oxide
NFC Natural fibre composites
NaOH Sodium hydroxide
SEM Scanning electron microscopy
W Weight gain
G
Wt% Weight %
Vol % Volume %
l/d Aspect ratio
DMTA Dynamic mechanical thermal analysis
DSC Differential scanning calorimetry
T Glass transition temperature
g
T Crystallisation temperature
C
T Melting temperature
m
ΔH Cold crystallisation enthalpy
cc
ΔH Melting enthalpy
m
Tex Mass of yarn in grams per 1,000 metres length

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