For turnouts as well, concrete sleepers have become widely and successfully accepted

305 Pages·2011·7.92 MB·English

Behaviour of Fibre Composite Sandwich
Structures: A case study on railway
sleeper application

By
Allan Manalo

Supervised by
Assoc. Prof. Thiru Aravinthan
Assoc. Prof. Karu Karunasena

A dissertation submitted for the award of
DOCTOR OF PHILOSOPHY

Centre of Excellence in Engineered Fibre Composites
Faculty of Engineering and Surveying
University of Southern Queensland
Toowoomba, Queensland, Australia
February 2011
Abstract

Timber is the most widely used material for railway sleepers; however, as a sleeper
material it deteriorates with time and needs appropriate replacement. Hardwood
timber for railway sleepers is becoming more expensive, less available and of
inferior quality compared to the timber previously available. This problem is
accentuated in railway turnouts where larger, longer, stronger and more expensive
timber is required. Research has therefore focused on the possibility of fibre
composites replacing timber as the many issues related to the currently used sleeper
materials could be simulated using this material.
This study is the first to investigate the concept of glue-laminated composite
sandwich beams for railway turnout sleepers. The building block of this innovative
beam is a novel composite sandwich structure made up of glass fibre composite skins
and modified phenolic core material that has been specifically developed for civil
engineering applications. The beam is produced by gluing layers of composite
sandwich structure together in different orientations, i.e. flatwise (horizontal) and
edgewise (vertical). This experimental beam enabled the author to determine the
more effective use of this composite material for structural beam applications. In this
way, a detailed understanding was achieved of the behaviour of the constituent
materials and composite sandwich structures to determine the suitability of this
construction system for railway sleepers.
An experimental study of the flexural and shear behaviour of the individual
sandwich structures in the flatwise and the edgewise positions was conducted. The
sandwich structures in the edgewise position possessed better structural performance
compared to the flatwise position due to the introduction of the vertical fibre
composite skins. The sandwich structure with the same dimensions in the edgewise
position displayed almost 20% and 70% higher failure load in bending and shear
respectively, than the sandwich structures in the flatwise position suggesting more
effective utilisation of the fibre composite material. This structure also exhibited
ductile failure behaviour which is important in the civil engineering perspective.
The effects of the number and the orientation of sandwich laminations on the
strength and failure behaviour of glue-laminated composite sandwich beams were
also examined. The glued sandwich beams with edgewise laminations have at least
25% higher flexural strength and over 20% in shear strength, compared to the
Behaviour of fibre composite sandwich structures: A case study on railway sleeper application i
individual sandwich beams. Gluing the sandwich beams in the edgewise position
could offer up to 25% increase in flexural strength, a similar bending stiffness, and
almost double the shear strength over beams in the flatwise position.
Theoretical prediction and numerical simulations were performed to gain a
better understanding of the structural behaviour of the composite sandwich
structures. Simplified Fibre Model Analysis (FMA) provides a preliminary indication
of the flexural behaviour, while the shear prediction equation gives a good estimation
of the shear strength of the sandwich structures. The Strand7 finite element program
predicted the behaviour up to failure load of the sandwich structures reasonably well.
This confirms that the behaviour and failure modes of composite sandwich structures
can be well predicted by simplified analysis procedures and by using the currently
available finite element software packages provided a good understanding of the
constituent materials and the individual sandwich lamination is known. These can be
important tools for design engineers permitting the design and development of fibre
composite sandwich structures with a higher degree of confidence.
A grillage beam analogy was implemented to investigate the behaviour of
sleepers and to obtain critical design parameters in a typical railway turnout system.
The effects of the elastic modulus of sleeper, support modulus, and spot replacement
were studied. All these factors have significant influences on the behaviour of
turnout sleepers. An elastic modulus of 4 GPa was found optimal for a fibre
composite turnout sleeper from the consideration of sleeper/ballast pressures and the
vertical deflection. It was established that the turnout sleeper has a maximum
bending moment of 19 kN-m and a shear force of 158 kN under service conditions.
Finally, the behaviour of the full-scale glue-laminated composite sandwich
beams in three different layouts was evaluated to determine their suitability as
railway turnout sleepers. The glued sandwich beams with edgewise laminations
presented appropriate strength and stiffness for replacement turnout timber sleeper.
The mechanical properties of these glue-laminated sandwich beams are comparable
with the existing timber turnout sleepers demonstrating that the innovative composite
sandwich beam is a viable alternative sleeper material for railway turnouts.
From this study, it is concluded that the glue-laminated composite sandwich
structures can be effectively used for replacement railway turnout sleepers. An
enhanced understanding of the behaviour of fibre composite sandwich structures for
potential civil engineering applications is an outcome of this investigation.
AC Manalo ii
Certification of Dissertation

I certify that the ideas, experimental work, results, analysis and conclusions reported
in this dissertation are entirely my own effort, except where otherwise
acknowledged. I also certify that the work is original and has not been previously
submitted for any award, except where otherwise acknowledged.

/ /
Signature of Candidate

Endorsed:

/ /
Signature of Supervisor/s

/ /
Signature of Supervisor/s

Behaviour of fibre composite sandwich structures: A case study on railway sleeper application iii
Acknowledgements

I would like to extend my deepest gratitude to my supervisor Assoc. Prof. Thiru
Aravinthan for giving me the opportunity to do a PhD at the University of Southern
Queensland (USQ). I am greatly indebted to him for his continuing confidence in me
as well as for giving me constant support throughout these years. He has been
involved in all the studies included in this dissertation and I have learnt many things
from his rich academic and practical experience. I am also thankful to my associate
supervisor, Assoc. Prof. Karu Karunasena. The discussions with him helped me
better understand numerical modelling; all his valuable suggestions were essential in
improving the quality of this research.
I greatly appreciate the academic, financial and technical support of the Faculty
of Engineering and Surveying and the Centre of Excellence in Engineered Fibre
Composites (CEEFC), which made this research possible. I would like to
acknowledge the USQ postgraduate scholarships awarded me to pursue my PhD
study. I especially thank Assoc. Prof. David Buttsworth, Associate Dean of
Research, for his continuous support that facilitated my work through the Faculty.
Thanks to Dr. Md. Mainul Islam, for all the helpful discussions and suggestions. I am
very thankful for the technical and administrative support from Wayne Crowell,
Martin Geach and Atul Sakhiya and to all the staff and postgraduate students at
CEEFC for the suggestions, support and friendship.
I would also like to thank Dr. Gerard Van Erp and the staff of LOC Composites
Pty. Ltd., Australia for the technical and materials support. The technical assistance
of Mr. Steve Douglas and Dr. Nick Stevens in the design and analysis of fibre
composite turnout railway sleepers is gratefully acknowledged.
The most important “thank you” goes to my dear wife, Jen. Thank you for your
love, for your endless patience, for comforting and encouraging me during the
challenging periods. Without your support I would not have been able to complete
this undertaking. I also want to thank my family who has always believed in my
capabilities. Thanks also to the Inocentes family who made our stay in Toowoomba
more enjoyable and memorable. To Almighty God for giving me the knowledge and
strength, thank you very much.
To those whom I failed to mention but have been a great part of this endeavour,
thank you very much.
AC Manalo iv
Associated Publications

Journal
Manalo, A.C., Aravinthan, T., Karunasena, W., and Ticoalu, A. (2010). A review on
alternative materials for replacement railway sleepers. Composite Structures, 92(3),
603-611.
Manalo, A.C., Aravinthan, T., Karunasena, W., and Islam, M. (2010). Flexural
behaviour of structural fibre composite sandwich beams in flatwise and edgewise
positions. Composite Structures, 92(4), 984-995.
Manalo, AC, Aravinthan, T. and Karunasena, W. (2010). In-plane shear behaviour of
structural fibre composite sandwiches using asymmetrical beam shear test.
Construction and Building Materials, 24(10), 1952-1960.
Manalo, A.C., Aravinthan, T. and Karunasena, W. (2010). Flexural behaviour of
glue-laminated fibre composite sandwich beams. Composite Structures, 92(11),
2703-2711.
Manalo, A.C., Aravinthan, T. and Karunasena, W. 2010. Shear behaviour of glued
structural fibre composite sandwich beams. Journal of Construction and Building
Materials (under review)
Manalo, A.C., Aravinthan, T., Karunasena, W., and Stevens, N. Analysis of a typical
turnout sleeper system with a low modulus of elasticity using grillage beam analogy.
Journal of Engineering Structures (under review)

Refereed Conference Proceedings
Manalo, A.C., Aravinthan, T. & Karunasena, W. (2009). Behaviour of laminated
beams from fibre composite sandwiches. Asia-Pacific Conference on FRP in
Structures (APFIS 2009), 9-11 December, Seoul, Korea, pp. 407-412.
Karunasena, W., Aravinthan, T., and Manalo, A.C. (2009). Vibration of debonded
laminated fibre composite sandwich beams. Asia-Pacific Conference on FRP in
Structures (APFIS 2009), 9-11 December, Seoul, Korea, pp. 457-462.
Manalo, A.C., Aravinthan, T., Karunasena, W., and Islam, M. (2009). Flexural
behaviour of composite sandwich for structural applications. The 9th International
Symposium on Fibre Reinforced Polymer Reinforcement for Concrete Structures
(FRPRCS9), 13-15 July, Sydney, Australia, pp. 26 (full paper in CD).
Manalo, A.C., Aravinthan, T. and Karunasena, W. (2010). Behaviour of structural
glulam beams from sustainable fibre composite sandwich panels. Proceedings of the
5th Civil Engineering Conference in the Asian Region and Australasian Structural
Engineering Conference (CECAR 5/ASEC), 8-12 August, Sydney, Australia, pp. 62
(full paper in USB).
Aravinthan, T., Manalo, A.C. and Douglas, S. (2010). Development of a fibre
composite turnout sleeper. Proceedings of the 5th Civil Engineering Conference in
the Asian Region and Australasian Structural Engineering Conference (CECAR
5/ASEC), 8-12 August, Sydney, Australia, pp. 34 (full paper in USB)
Behaviour of fibre composite sandwich structures: A case study on railway sleeper application v
Manalo, A.C., Aravinthan, T. and Karunasena, W. (2010). Shear behaviour of glue-
laminated composite sandwich beams. The 5th International Conference on FRP
Composites in Civil Engineering (CICE 2010), 27-29 September, Beijing, China, pp.
139-143.
Manalo, A.C., Aravinthan, T. and Karunasena, W. (2010). A comparison of the shear
behaviour of a fibre composite sandwich structure in the transverse and in-plane
directions. Proceedings of the 21st Australasian Conference on the Mechanics of
Structures and Materials (ACMSM21), 7-10 December, Victoria University,
Melbourne, Australia, pp. 421-426.
Manalo, A.C., Aravinthan, T., Karunasena, W., and Stevens, N. (2010). The effect of
modulus of elasticity on the behaviour of railway turnout sleepers. Proceedings of
the 21st Australasian Conference on the Mechanics of Structures and Materials
(ACMSM21), 7-10 December, Victoria University, Melbourne, Australia, pp. 427-
432.
Manalo, A.C., Aravinthan, T., and Karunasena, W. (2010). Evaluation of the strength
and stiffness of glue-laminated fibre composite sandwich panels for structural beam
application. Proceedings of the 6th Australasian Congress on Applied Mechanics
(ACAM 6), 12-15 December, Perth, Western Australia, 10 p. (Conference
proceedings in digital USB)
Manalo, A.C., Aravinthan, T., Karunasena, W., and Douglas, S. (2010). Fibre
composite sandwich beam: An alternative to railway turnout sleeper? Proceedings of
the 2010 Southern Region Engineering Conference, 12 November, University of
Southern Queensland, Toowoomba, Queensland, 8 p. (Paper no. F1-2, Conference
proceedings in website: http://www.usq.edu.au/engsummit/proceedings)

AC Manalo vi
Table of Contents

List of figures xiii
List of tables xviii
Notations xx

Chapter 1 Introduction
1.1 General 1
1.2 Background on hardwood timber sleepers 2
1.3 Fibre composites as an alternative for sleeper applications 5
1.4 Fibre composite railway sleepers using sandwich structures 5
1.5 Objectives 7
1.6 Scope of the thesis 8
1.7 Outline of the thesis 9
1.8 Summary 10

Chapter 2 A review of alternative materials for timber sleepers
2.1 General 11
2.2 Sleeper replacement strategies 11
2.3 Existing materials for railway sleepers 12
2.3.1 Hardwood timber 12
2.3.2 Softwood and engineered timber 14
2.3.3 Prestressed concrete 16
2.3.4 Steel 17
2.4 The need for alternatives 19
2.5 Fibre composite alternatives 21
2.5.1 Combinations with other materials 21
2.5.2 Strengthening of existing sleepers 25
2.6 R&D on innovative fibre composite sleepers 27
2.7 Properties of existing timber railway sleepers 29
2.8 Fibre composite sandwich structures 32
2.9 Recent developments in composite sandwich structures 35
2.10 Applications of sandwich structures in civil engineering 39
2.11 Novel composite sandwich structures for railway sleepers 41
2.12 Conclusions 43

Chapter 3 Characterisation of the constituent materials of a novel composite
sandwich structure
3.1 Introduction 45
3.2 Material under study 46
3.3 Characterisation of the fibre composite skin 47
Behaviour of fibre composite sandwich structures: A case study on railway sleeper application vii
3.3.1 Flexural test 48
3.3.2 Tensile test 49
3.3.3 Compressive test 52
3.3.4 Shear test 53
3.4 Core characterisation 56
3.4.1 Flexural test 56
3.4.2 Dog-bone tensile test 58
3.4.3 Compressive test 59
3.4.4 Shear test 62
3.5 Summary of mechanical properties of the skin and core 65
3.5.1 Validity of test results 66
3.5.2 Behaviour of bi-axial (0/90) glass fibre laminates 66
3.5.3 Behaviour of the phenolic core 67
3.6 Conclusions 69

Chapter 4 Flexural behaviour of fibre composite sandwich structures in
flatwise and in edgewise positions
4.1 Introduction 70
4.2 Experimental program 71
4.2.1 Test specimen 71
4.2.2 Test set-up and procedure 72
4.3 Experimental results and observations 73
4.3.1 Load-deflection behaviour 73
4.3.2 Stress-strain behaviour of fibre composite skins 75
4.3.3 Failure behaviour 77
4.4 Estimation of the failure load and mechanisms 79
4.4.1 Skin failure 80
4.4.2 Core shear failure 81
4.4.3 Core failure in tension and compression 82
4.5 Analytical prediction of the sandwich structure behaviour 82
4.5.1 Fibre Model Analysis 82
4.5.2 Failure load 86
4.5.3 Flexural stiffness 86
4.5.4 Load deflection behaviour 88
4.6 Finite element modelling of sandwich structure behaviour 89
4.7 Predicted results and comparison with experiments 91
4.7.1 Failure load 91
4.7.2 Stress-strain behaviour of fibre composite skins 93
4.7.3 Load-deflection relationship of sandwich structures 95
4.7.4 Failure behaviour 97
4.8 Conclusions 98

AC Manalo viii
Chapter 5 Shear behaviour of fibre composite sandwich structures with high
strength core material
5.1 Introduction 100
5.2 Shear test for composite sandwich structures 101
5.3 Experimental program 104
5.3.1 Test specimen 104
5.3.2 Test set-up and procedure 106
5.4 Experimental results and discussion 106
5.4.1 Failure load 106
5.4.2 Load and crosshead displacement behavior 107
5.4.3 Stress-strain behavior 107
5.4.4 Failure behavior 110
5.5 Theoretical evaluation of the shear strength 112
5.5.1 Composite sandwich beam equations 112
5.5.2 American Plywood Association, 1995 112
5.5.3 Concrete beams with bonded steel and FRP plates 113
5.5.4 Triantafillou, 1998 114
5.5.5 Kawasaki et al., 2003 115
5.5.6 Proposed shear strength equation 115
5.6 Predicted shear strength and comparison with experiments 117
5.7 Modelling of the shear behaviour of sandwich structures 118
5.7.1 FEM of composite sandwich structures 118
5.7.2 Failure load 119
5.7.3 Stress-strain relationship 120
5.7.4 Failure behaviour 121
5.8 Conclusions 122

Chapter 6 Behaviour of glue-laminated fibre composite sandwich beams
6.1 Introduction 123
6.2 Experimental program 125
6.2.1 Test specimen and preparation 125
6.2.2 Test set-up and procedure 127
6.3 Flexural behaviour of glue-laminated sandwich beams 127
6.3.1 Experimental results and observation 127
6.3.2 Effect of number of laminations on stiffness 133
6.3.3 Effect of number of laminations on strength 135
6.3.4 Effect of beam orientation on failure behaviour 137
6.4 Shear behaviour of glue-laminated sandwich beams 138
6.4.1 Experimental results and observations 138
6.4.2 Effect of number of laminations on shear strength 142
6.4.3 Effect of beam orientation on failure behaviour 143
6.4.4 Effect of shear span-to-depth ratio on strength 144
6.5 Evaluation of glue-laminated sandwich beam behaviour 145
Behaviour of fibre composite sandwich structures: A case study on railway sleeper application ix