EFFECT OF STITCH PARAMETERS ON TENSILE AND LOW VELOCITY IMPACT PERFORMANCE OF EMPTY FRUIT BUNCH OIL PALM FIBER EPOXY COMPOSITE
BY
AHMAD LUQMAN BIN AHMAD GHAZILAN
A thesis submitted in fulfilment of the requirement for the degree of Master of Science (Mechanical Engineering)
Kulliyyah of Engineering
International Islamic University Malaysia
JANUARY 2018
ii
ABSTRACT
Empty fruit bunch (EFB) from oil palm has become one of the widely used natural fiber reinforced composites since it possesses specific properties that offer exceptional performance for structural load bearing applications. However, overall mechanical performances of EFB oil palm composites have been limited due to its hydrophilic characteristic. It is essential to enhance the in-plane and out-of-plane mechanical performances of EFB oil palm fiber composites by using advanced reinforcement method of through thickness stitching. Stitching parameters consisting of thread thickness, stitching density and stitching orientation are investigated to evaluate the tensile performance of its composite structure. Pitch length of 10 mm and 15 mm were used for stitch density variation, thread thickness of Nylon 210D and Polyester 380D for thread thickness variation, stitching pattern of 00,450, and 900 were used for stitching orientation variation. Result of mechanical characterization tests of unstitched palm fiber composites and mechanical properties of a single strand of stitch material are analyzed and updated in the simulation model. The finite element analysis study evaluates low velocity impact test of z-directional stitching for EFB oil palm fiber composite by employing LS-DYNA software as its analysis tool. Several sets of investigations were carried out to study the influence of stitch density and thread thickness on their impact response when subjected to low velocity impact. Pitch length of 6 mm and 10 mm were used for stitch density variation, whereas, thread thickness of 1 mm (Nylon 210D) and 1.5 mm (Polyester 380D) for thread thickness variation. Experimental test case of low velocity impact test of unreinforced polyester and random oriented non-woven hemp fiber polyester reinforced composite plates were used to validate the finite element model. Outputs of maximum load, energy absorption, and failure behavior for impacted specimens of experimental and simulation results were compared. Tensile strength and modulus elasticity decrease by 61% and 38% respectively when oil palm fiber composite is compared to unreinforced epoxy. Tensile strength and modulus of elasticity of stitched EFB oil palm fiber composite have improved by 66% and 46% respectively when compared to unstitched composite due to the additional load bearing capability and compaction effect from the increase in fiber volumetric fraction of stitch threads. High dense stitch density, thinner thread thickness, longitudinal orientation stitched EFB composite have corresponded to a higher tensile performance when compared to its predecessor.
Impacted stitched EFB fiber reinforced composite exhibit superior load bearing capability when compared to unstitched EFB composite. The energy absorption for unstitched, 6 mm x 6 mm stitch density, and 10 mm x 10 mm stitch density stitched EFB composite were recorded at 0.143, 0.368, and 0.158 J respectively. High dense stitch density and thinner thread thickness stitched EFB composite have corresponded to a higher maximum load, higher force and displacement level for the occurrence of structural degradation, and higher amount of energy absorption. Impacted specimen exhibits fragmented fracture due to its nature of brittle failure behavior. Matrix cracking, fiber breakage, and penetration of impacted surface were the composite damage mechanism of stitched EFB composite.
iii
ةصلاخ ثحبلا
ABSTRACT IN ARABIC
حبصأ روشق
ةرمثلا ةغرافلا
نم جرختسملا تيز
ليخنلا ادحاو
نم رثكا تابكرم
فايللأا ةيعيبطلا
ةززعملا امادختسا
امل هيف نم صئاصخ ةيعون
هيطعت أءادا
ازاتمم
نيح همادختسا يف
لكايهلا ةلماحلا
ءادا نإف ،كلذ عم و . صئاصخلا
ةيكيناكيملا
تابكرمل فايللأا
ةيعيبطلا دودحم
ارظن ةيلباقل صاصتما ءاملا
اهيف يرورضلا نم .
ةكيمسلا زرغلا بولسا مادختساب ةيعيبطلا فايللاا تابكرمل يكيناكيملا ءادلاا ريوطت و .مدقتملا نم
مث تمت ةسارد تاريغتملا
يف
،فايللاا و
يه كمُس : ةلتفلا و ةفاثك
طويخلا و
اههجوت نيسحتل
ءادأ لكيهلا ةنورم .بّك َرُملا
ةلتفلا لاوطا مادختسا مت 01
و ملم 01 نوليان نم طيخ و ،ةزرغلا ةفاثك رييغتل ملم رتسيلوبلا نم رخا و 210D
ةكايحلا يطمنو ،كمسلا رييفتل 380D , 90
0,45
00
0هجوت يف مكحتلل امدختسا
مث .ةكايحلا ةلتفلل اهصئاصخ و تابكرملل يكيناكيملا فينصتلا تارابتخا جئاتن لخدت
.بوساحلا زاهج ىلع رابتخلاا ءارجلا يضارتفلاا جذومنلا يف ةكاحملا ىرجي
مييقت
رابتخا مداصتلا
ةعرسلاب ةضفخنملا
ىلع روحملا ينيعلا
نع قيرط ةسارد
ليلحت
تايئزجلا لا
ةيهانتم ىلع
جمانربلا يليلحتلا
LS-DYNA تيرجأ .
ةدع تاعومجم
نم براجتلا ةساردل
ريثأت ةفاثك ةكامسو فايللأا
ىلع ىدم اهتباجتسا امدنع
ضرعتت
مادطصلإل ةعرسب
ةضفخنم مت.
ديدحت لوط ةوطخلا نيب
ملم 6 و ملم 10 ديدحتل ةفاثك
و،فايللاا 0
نوليانلا ملم 210D
و 1.5 ملم رتسيلوبلا ديدحتل 380D
تاجرد كمسلا
.
دعبو لوصحلا ىلع
جئاتن تارابتخا تامادطصا
ةعرسلا ةضفخنملا
،ةيبيرجتلاا متي
مييقت .جذومنلا ةحص نم ققحتلل ةبرجتلا قيرط نع جئاتنلا تاجرخم ةنراقم تمت
ايبيرجت اهرابتخا مت ىتلا تانيعلل لشفلا كولسو ،ةقاطلا صاصتماو ،ىصقلأا لمحلا عم ةاكاحملا جذومن جئاتن ةبسنب ةنورم لماعمو دشلا ةوق ضفخنت .
% 60 و
% 83
ىوقملا ريغ يسكوبيلإاب ليخنلا تيز فايلأ بكرم ةنراقم متت امدنع يلاوتلا ىلع .
اعمو دشلا ةوق تنسحت دقو ةبسنب ةبكرملا فايللأا ةنورم لم
% 66 و
% 66 ىلع
حلا ةردق ببسب طيخم ريغ بكرم عم ةنراقملاب يلاوتلا ةئبعتلا ريثأتو ةيفاضلإا لم
يلوطلا هاجتلااو ،عيفرلا طيخلا و ،زرغلل ةيلاعلا ةفاثكلا.زرغلا ةفاثك ةدايز نم حتانلا اهتقباس عم ةنراقملاب ىلعأ ةنورم ءادأ عم قفاوتت بكرملا ةكايح يف ةنيعلل ناك و .
ريغلا ةنيعلا نم لقثا نازوا لمحتل ىلعا ةيلباق تامدصلل ةضرعملا ةززعملا .ةززعم
مجحب زرغلا تاذ و ةطيخم ريغلا تانيعلا نم لكل ةقاطلا صاصتما ةيمك تلجس 6
ملم
6 x مجحب زرغلا تاذ ةنيعلا و ملم 01
ملم 01 x
جئاتنلا تناك و ملم 0.143J
و ،
0.368J و ،
0.158J .يلاوتلا ىلع
دقو تطعا ةنيعلا
تاذ ةفاثكلا ةيلاعلا
و طويخلا
قرلاا اكمس
لضفا جئاتنلا
يف ربكا لمح و ربكا ةوق و ةجرد ةحازا
و صاصتما
ةقاط ربكا و . دق انظحلا ضعب
تارسكتلا ةقرفتملا
تانيعلاب يتلا
تمت اهيلع براجت
مداصتلا و
كلذ اهتعيبطل ةشهلا
و تناك هذه تارسكتلا ةيلخادلا
ىلع طمن
،قرفتم ىلع
قاطن طيخلا و
تدا ىلا قارتخا يحطس
.
iv
APPROVAL PAGE
I certify that I have supervised and read this study and that in my opinion, it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a thesis for the degree of Master of Science (Mechanical Engineering).
……….
Hanan Mokhtar Supervisor
……….
Mohd Sultan Ibrahim Shaik Dawood
Co-Supervisor
I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a thesis for the degree of Master of Science (Mechanical Engineering).
……….
Yulfian Aminanda Internal Examiner
……….
Rozli Zulkifli External Examiner
This thesis was submitted to the Department of Mechanical Engineering and is accepted as a fulfilment of the requirement for the degree of Master of Science (Mechanical Engineering).
……….
Meftah Hrairi
Head, Department of Mechanical Engineering
This thesis was submitted to the Kulliyyah of Engineering and is accepted as a fulfilment of the requirement for the degree of Master of Master of Science (Mechanical Engineering).
……….
Erry Yulian Triblas Adesta Dean, Kulliyyah of Engineering
v
DECLARATION
I hereby declare that this dissertation is the result of my own investigations, except where otherwise stated. I also declare that it has not been previously or concurrently submitted as a whole for any other degrees at IIUM or other institutions.
Ahmad Luqman Bin Ahmad Ghazilan
Signature ... Date ...
vi
COPYRIGHT PAGE
INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA
DECLARATION OF COPYRIGHT AND AFFIRMATION OF FAIR USE OF UNPUBLISHED RESEARCH
EFFECT OF STITCH PARAMETERS ON TENSILE AND LOW VELOCITY IMPACT PERFORMANCE OF EMPTY FRUIT
BUNCH OIL PALM FIBER EPOXY COMPOSITE
I declare that the copyright holders of this dissertation are jointly owned by the student and IIUM.
Copyright © 2018 Ahmad Luqman Bin Ahmad Ghazilan and International Islamic University Malaysia. All rights reserved.
No part of this unpublished research may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without prior written permission of the copyright holder except as provided below
1. Any material contained in or derived from this unpublished research may be used by others in their writing with due acknowledgement.
2. IIUM or its library will have the right to make and transmit copies (print or electronic) for institutional and academic purposes.
3. The IIUM library will have the right to make, store in a retrieved system and supply copies of this unpublished research if requested by other universities and research libraries.
By signing this form, I acknowledged that I have read and understand the IIUM Intellectual Property Right and Commercialization policy.
Affirmed by Ahmad Luqman Bin Ahmad Ghazilan
……..……….. ………..
Signature Date
vii
ACKNOWLEDGEMENTS
Firstly, it is my utmost pleasure to dedicate this work to my dear wife, child, parents and my family, who granted me the gift of their unwavering belief in my ability to accomplish this goal: thank you for your support and patience.
I wish to express my appreciation and thanks to those who provided their time, effort and support for this project. To the members of my dissertation committee, thank you for sticking with me.
Finally, a special thanks to Dr. Hanan Mokhtar and Dr. Mohd Sultan for their continuous support, encouragement and leadership, and for that, I will be forever grateful.
viii
TABLE OF CONTENTS
Abstract ... ii
Abstract in Arabic ... iii
Approval Page ... iv
Declaration ... v
Copyright ... vi
Acknowledgements ... vii
Table of Contents ... viii
List of Tables ... x
List of Figures ... xi
List of Abbreviations ... xiii
List of Symbols ... xiv
CHAPTER ONE: INTRODUCTION ... 1
1.1 Background of the Study ... 1
1.2 Statement of the Problem... 2
1.3 Research Objectives... 3
1.4 Research Methodology ... 3
1.5 Research Scopes ... 5
1.6 Significance of the Study ... 7
1.7 Thesis Outline ... 8
CHAPTER TWO: LITERATURE REVIEW ... 9
2.1 Natural Fiber Composite Overview ... 9
2.1.1 Mechanical Properties of Natural Fiber ... 11
2.1.2 Matrices for Natural Fiber Composites ... 12
2.2 Oil Palm Fiber Composite Overview ... 14
2.2.1 Background, Morphology and Classification ... 14
2.2.2 Mechanical Properties of Oil Palm Fiber Composite ... 18
2.3 Composite Manufacturing Processes ... 19
2.3.1 Overview Process ... 20
2.3.2 Factors Influencing Processing ... 20
2.3.3 Vacuum Bagging... 21
2.4 Effect of Stitching Parameters on Conventional Composite Properties ... 24
2.4.1 The Micromechanics Failure of Stitched Composites ... 26
2.4.2 Advantages and Disadvantages of Stitching ... 27
2.4.3 Stitching Parameters ... 28
2.5 Finite Element Analysis of Stitched Composites ... 31
2.6 Chapter Summary ... 34
CHAPTER THREE: RESEARCH METHODOLOGIES ... 35
3.1 Stage 1: Random Untreated Pre-Form EFB Oil Palm Fiber Layer Preparation ... 36
3.2 Stage 2: Unreinforced Epoxy and EFB Oil Palm Fiber Epoxy Reinforced Composite Fabrication Process ... 37
ix
3.3 Stage 3: Stitched EFB Oil Palm Fiber Reinforced Epoxy Composite
Fabrication Process ... 38
3.4 Stage 4: Mechanical Testing of EFB Oil Palm Fiber Epoxy Reinforced Composite and Stitch Material ... 42
3.5 Stage 5: Finite Element Modelling and Analysis of EFB Oil Palm Composites ... 44
3.5.1 Finite Element Modelling for Material and Model Validation ... 47
3.5.2 Finite Element Modelling of Low Velocity Impact Test ... 49
3.6 Chapter Summary ... 52
CHAPTER FOUR: RESULTS AND DISCUSSIONS ... 53
4.1 Tensile Performance Of Stitched Efb Oil Palm Fiber Composite ... 53
4.1.1 Mechanical Performances of Unreinforced Epoxy, Unstitched and Stitched EFB Oil Palm Fiber Composite ... 54
4.1.2 Stitch Density Variation on the Performance of Stitched EFB Fiber Composite ... 57
4.1.3 Stitch Thread Thickness Variation on the Performance of Stitched EFB Fiber Composite ... 59
4.1.4 Stitch Pattern Variation on the Performance of Stitched EFB Fiber Composite ... 61
4.2 Finite Element Analysis Result Validation... 63
4.3 Low Velocity Impact Test ... 69
4.3.1 Load-Time and Load-Displacement Impact Responses ... 69
4.3.2 Energy Absorption and Impact Damage Characteristics ... 75
4.4 Chapter Summary ... 78
CHAPTER FIVE: CONCLUSIONS AND RECOMMENDATIONS ... 79
5.1 Conclusion ... 79
5.2 Research Contributions ... 80
5.3 Recommendation for Future Work ... 83
REFERENCES ... 85
LIST OF PUBLICATION ... 92
APPENDIX A: RESEARCH MILESTONES ... 93
x
LIST OF TABLES
Table No. Page No.
2.1 Vacuum Bagging Parts 23
3.1 Plain Epoxy and EFB Fiber Epoxy Composite Specimen Parameters 38 3.2 Variation of Stitch Thread Thickness Specimen Parameters 41
3.3 Variation of Stitch Density Specimen Parameters 41
3.4 Variation of Stitch Pattern Specimen Parameters 42
3.5 EFB Composite Engineering Parameters and Stitch Threads
Characterizations 45
3.6 Material Parameter Input for Simulation Validation 49
3.7 Details of Modelling 51
4.1 Tensile Performances Unreinforced Epoxy, Unstitched and Stitched
EFB Composites 54
4.2 Tensile Properties of Stitched EFB Composites under Different Stitch
Density 57
4.3 Tensile Properties of Stitched EFB Composites for Different Thread
Thickness 59
4.4 Tensile Properties of Stitched EFB Composites for Different Stitch
Orientation 62
4.5 Tensile Properties of EFB Oil Palm Composites 64
4.6 Experimental and Simulation Results of Peak Load and Energy
Absorption 68
4.7 Low Velocity Impact Test – Peak Load Results 69
4.8 Low Velocity Impact Test-Energy Absorption Results 75
xi
LIST OF FIGURES
Figure No. Page No.
1.1 Research Methodology Flowchart 5
2.1 Oil Palm Tree in Malaysia 15
2.2 Cross Section of Full Fruit Bunch 15
2.3 Disposal of Palm Oil Product 16
2.4 Scanning Electron Microscopic Cross Sectional Section of Oil Palm
Fiber 17
2.5 Vacuum Bagging Process 22
2.6 Stiching Methods 26
3.1 Stages of Research Methodology Flowchart 36
3.2 Pre-Form Palm Fiber Layer Preparation 37
3.3 Vacuum Bagging Fabrication Process 37
3.4 Modified Lock Stitch Method and Schematic View of Stitching 39
3.5 Sample of Manually Stitched Dry Palm Fiber Layers 39
3.6 Stitch Density Variation Sample Specimen 40
3.7 Stitch Orientation Variation Sample Specimen 40
3.8 ASTM D 638 Tensile Specimen Specifications 42
3.9 CNC Milling Cutting Process and Tensile Test Specimens 43
3.10 Model of Vertical Stitches 46
3.11 Stitch Attachment at Bottom and Top Sublaminate Surface 47 3.12 Cross Sectional View of Plate Model with Stitching Thread Model 47 3.13 Tensile Test of EFB Composite for a) Unstitched Specimen and b)
Stitched Specimen 48
3.14 Low Velocity Impact Test Specimen for a) Unstitched and b) 6mm x
6mm, Nylon 210D 50
xii
3.15 Low Velocity Impact Test Specimen for a) 10mm x 10mm, Nylon
210D and b) 10mm x 10mm, Polyester 380D 50
4.1 Stress vs Strain Curves of Unreinforced Epoxy, Unstitched and Stitched
EFB Composites 54
4.2 Stress vs Strain Curves of Stitch Density Variation 57 4.3 Stress vs Strain Curves of Thread Thickness Variation 59 4.4 Stress vs Strain Curves of Stitch Orientation Variation 62
4.5 Tensile Stress vs Strain Curves 64
4.6 Energy Absorption Curves for Unreinforced Polyester and Hemp Fiber
Composite 66
4.7 Load-Time Impact Curves for Unreinforced Polyester and Hemp Fiber
Composite 66
4.8 After Impact Front (left) and Back (right) Surface of Experimental Test
Case Unreinforced Polyester 67
4.9 After Impact Front (left) and Back (right) Surface of Simulated
Unreinforced Polyester 67
4.10 After Impact Front (left) and Back (right) Surface of Experimental
Test Case Hemp Fiber Composite 67
4.11 After Impact Front (left) and Back (right) Surface of Simulated Hemp
Fiber Composite 68
4.12 Typical Damage Stages for Impacted Specimen 70
4.13 Stitch Density Variation Force-Time Impact Curves at 1.10 m/s
Impactor Velocity 71
4.14 Thread Thickness Variation Force-Time Impact Curves at 1.10 m/s
Impactor Velocity 73
4.15 Stitch Density Variation Force-Displacement Impact Curves at 1.10
m/s Impactor Velocity 73
4.16 Thread Thickness Variation Force-Displacement Impact Curves at
1.10 m/s Impactor Velocity 74
4.17 After Impact Surface Penetration for Unstitched EFB Composite (left)
and 10 mm x 10 mm Stitch Density EFB Composite (right) 77 4.18 After Impact Surface Penetration for 6 mm x 6 mm Stitch Density EFB
Composite (left) and 380D Thread Thickness EFB Composite (right) 77
xiii
LIST OF ABBREVIATIONS
𝐸𝐹𝐵 Empty Fruit Bunch
𝑆𝑂𝑃𝐹𝐶 Stitched Oil Palm Fiber Composites
𝑀𝐴𝑃𝑃 Maleic Anhydride Polypropylene-g-polypropylene
𝑅𝑇𝑀 Resin Transfer Molding
𝑉𝐴𝑅𝑇𝑀 Vacuum Assisted Resin Transfer Molding
𝑈𝑅𝐸 Unreinforced Epoxy
𝑈𝑃𝐸 Unreinforced Polyester
𝐶𝑁𝐶 Computer Numerical Control
xiv
LIST OF SYMBOLS
℃ Degree Celsius
𝜇𝑚 Micrometer
𝑀𝑃𝑎 Mega Pascal
𝐺𝑃𝑎 Giga Pascal
% Percentage
𝑚𝑚 Millimeter
𝑘𝑔 Kilogram
𝑎𝑡𝑚 Atmospheric
𝑝𝑠𝑖 Pascal per square inch
1𝐷 1-Dimensional
3𝐷 3-Dimensional
𝐷 Denier
° Degree
𝑚𝑖𝑛 Minute
𝑠 Second
𝐽 Joule
𝑃𝑚𝑎𝑥 Maximum force
𝑘𝑁 Kilo Newton
𝑚𝑠 Millisecond
𝑚 Mass
𝐸 Impact Energy
𝑣𝑖 Initial velocity
𝑣𝑓 Final velocity
1
CHAPTER ONE INTRODUCTION
1.1 BACKGROUND OF THE STUDY
In recent years, there have been growing interest in natural fiber-polymeric composites due to the increase in public concern and awareness of the environmental impact of man-made materials. Natural fiber from renewable natural resources have shown potential as a biodegradable reinforcing material when compared to synthetic fiber such as glass fibers. Natural fibers provide advantageous properties such as low cost, low density, biodegradability, and good thermal and insulating properties (Sgriccia, Hawley, & Misra, 2008). A composite is a complex solid material combining or mixing two or more different materials resulting in an enhanced, improved and superior material. In the mechanism of how fiber-reinforced-composite material serves it purposes in enhancing its specific properties, the fibrous material acts as reinforcing backbone by providing strength stiffness to the structure while the polymer matrix serves as interfacial adhesive bond to hold the reinforcement fiber intact.
The growing interest in natural fiber especially oil palm fiber from empty fruit bunch (EFB) is mainly due to their environmental advantages, economical production from biodegradable waste with few required equipment, and low specific weight corresponding to high specific strength and stiffness compared to conventional- synthetic fiber composition (Mahjoub, Bin Mohamad Yatim, & Mohd Sam, 2013).
However, regarding their low mechanical strength as compared to conventional synthetic composite fibers during loading application, natural fiber composite is
2
considered as inadequate or limited in handling loading applications. Thus, it is essential to enhance the mechanical performance of natural fiber composite.
In recent years, the use of composite structures have become common in wide range of engineering application. Due to their superior specific mechanical properties, they have provided numerous benefits when compared to conventional materials.
Despite having various advantages of using fiber-reinforced composite materials in engineering applications, laminated composite structures still need to overcome their primary drawback of poor through thickness mechanical strength (Tong, Mouritz, &
Bannister, 2002). Stitching has become and proven to be effective in suppressing the damage growth in composite materials. Bridging effect caused by through thickness reinforcement of stitching significantly reduced the driving force of crack tip from full propagation thus raising the ultimate strength. The driven factors of through thickness reinforcement development were the demand of reducing fabrication cost, increasing through thickness mechanical properties of a laminate composites and improving the impact resistance of fiber reinforced composites (Abrate, 2005).
1.2 STATEMENT OF THE PROBLEM
Empty fruit bunch oil palm fiber is categorized as a natural fiber polymeric reinforced composite with benefits such as environmental advantages in terms of economical production from biodegradable waste, low specific weight to high specific strength and stiffness. However, their mechanical strength is low when compared to conventional inorganic synthetic fiber polymeric reinforced composite during loading applications, and is consider as inadequate or limited in handling the loading application. Thus, it is essential to enhance the mechanical performance of natural
3
fiber composites especially in-plane and out-of-plane loading conditions by using advanced reinforcement method such as through thickness reinforcement of stitching.
1.3 RESEARCH OBJECTIVES
The study aims to achieve the following objectives:
1. To obtain the tensile performance of unstitched and stitched empty fruit bunch oil palm fiber reinforced epoxy composites manufactured using vacuum bagging fabrication technique when subjected to different stitch parameters.
2. To analyze the tensile performance of stitched empty fruit bunch oil palm fiber reinforced epoxy composites with various stitch parameters.
3. To analyze the low velocity impact response of stitched empty fruit bunch oil palm fiber epoxy reinforced composites with different stitch parameters by means of finite element analysis.
1.4 RESEARCH METHODOLOGY
In order to achieve the stated research objectives, the following steps are taken over the course of this research:
1. Literature Review. Previous work in the detection and classification of natural fiber, fabrication process, through thickness reinforcement, finite element analysis for stitched EFB oil palm reinforced epoxy composite were gathered and studied thoroughly. Highlighting the approaches to evaluate and predict the tensile and low velocity impact performance.
2. Research Methodology. From existing design of fabrication and test, the most suitable technique of natural fiber composite fabrication, stitching process and parameters, experimental procedures and finite element modelling with the
4
feasibility for evaluation on the performance of stitched EFB oil palm fiber composite were chosen.
3. Performance Evaluation. Tensile and low velocity impact performance analysis were carried out using quantitative measures. The tensile strength, modulus of elasticity, load-time response, displacement response, and energy absorption response of the stitched structure are compared against unreinforced structure, unstitched structure and several significant related works using public datasets.
Figure 1.1 shows the flowchart of the research methodology used in conducting this research, beginning from the literature review to the performance evaluation. Each respective research objective can be achieved after undergoing certain stages. The first objective is achieved after the fabrication process of URE, unstitched and stitched of untreated EFB oil palm fiber epoxy reinforced composite plate are fulfilled. The second objective is achieved after the tensile mechanical testing of stitched EFB oil palm fiber epoxy reinforced composite. The third objective is achieved after the finite element modelling and analysis of tensile and low velocity impact test.
5
Figure 1.1 Research Methodology Flowchart
1.5 RESEARCH SCOPES
The scope of this research is listed as follows:
1. Untangled, random and equally distributed EFB oil pam fiber layer used for composite plate fabrication was remain untreated in order to preserve the preliminary composite structure quality and avoid additional fabrication process. Thus, fiber pre-treatment is not considered in this research.
6
2. Fiber volumetric fraction is not varied in this research. EFB oil palm fiber epoxy reinforced composite plates are fabricated using vacuum bagging manufacturing technique at 20 % fiber volume fraction. Bottom and upper stainless steel plate with flexible resin stoppers are used as a mold in order preserve uniform composite plate thickness.
3. Stitching process of single layer dry EFB oil palm fiber is restricted to manual sewing procedures without using any industrial or household grade sewing machine. In order to minimize in plane fiber distortion inside fiber structure caused by intersection point loop of chain stitch or lock stitch method, modified lock stitch method is chosen as the only type of stitching method for this study.
4. The stitching parameter was limited to three classes of variations: stitch density, thread thickness, and stitching orientation. These three categories were chosen to be the main focus of this study. Since sewing is restricted with manual procedures, variation of stitching parameters are chosen as follows: 10 mm and 15 mm stitch density, Nylon 210D (0.872 mm) and Polyester 380D (1.233 mm) thread thickness, and 00,450, and 900 stitching orientation.
5. Tensile test of EFB oil palm fiber composites are conducted as per ASTM D 638 specifications using Universal Testing Machine INSTRON 5582. Tensile test stitch thread material are conducted as per ASTM D 2256 specifications using Universal Testing Machine Shimadzu AGS-X 5kN. Low velocity impact test of composite structure are as per ASTM D 7136 specifications.
6. Material characteristics of EFB oil palm fiber composite and thread material serve as an input parameter for finite element modelling. Due to limited datasets, finite element modelling of natural fiber composite structure
7
subjected to low velocity impact test are validated using public test case and datasets of unreinforced polyester plate and hemp fiber composite structure.
7. Due to short and random oriented fiber material used in this study, material failure are represented using isotropic material characteristics. Both plate and stitch structure are modeled as solid element. Plate element size is refined at the vicinity of stitches, with a modelling simplification and conversion of two parallel stitch circular areas into one stitch square area.
8. Due to the usage of single layer fiber, experiments of unstitched and stitched EFB oil palm fiber composite subjected to tensile and low velocity impact test are conducted to evaluate the structure’s performance by excluding the evaluation for delamination damage characteristics.
1.6 SIGNIFICANCE OF THE STUDY
In this perspective, mechanical performance of stitched oil palm fiber composites (SOPFC) extracted from empty fruit bunch are investigated. This new concept is important to develop an engineering understanding of the effect of stitch parameters on mechanical strength of thin composite plates. In principle, stitches would provide greater structural stability and integrity across the cross section thus enhancing the overall mechanical performance in terms of tensile, shear, bending rigidities and energy absorption index. The study understating the stitch effect would provide a basis for further research activities for performance enhancement of natural fiber composites and possible structural applications with greater load bearing capabilities.
The assessment of this research would expand the current knowledge and thus will be expected to recognize specific design, fabrication and pattern of stitched palm fiber composite which will offer a dependent solution on the usage of bio waste from
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local oil palm industry toward better innovation and development. From this study, it would provide comprehensive knowledge on related natural fiber, mechanical performances, composite manufacturing techniques, stitched composites and its finite element analysis. It would also offer a desirable solution for the recycling of biodegradable waste from local as well as global markets of oil palm industries thus aiding the national toward sustainability and economic development in green technology.
1.7 THESIS OUTLINE
This thesis consists of five chapters. Chapter 1 describes the overview, followed by the background of this study. The problem statement, research objectives, research methodologies, research scope and significance of the research are included in this chapter. Chapter 2 discusses previous works done by other researchers on stitched EFB oil palm composite structure. Chapter 3 presents the methodology for the fabrication and tests of stitched EFB oil palm composite. This includes fiber preparation, stitching process, composite fabrication, mechanical tests, and finite element modelling and analysis. In Chapter 4, the performance of the URE, unstitched and stitched EFB oil palm composite in terms of tensile and low velocity impact response are evaluated and discussed. Chapter 5 highlights the conclusion and the recommendations for future work in this area.
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CHAPTER TWO LITERATURE REVIEW
2.1 NATURAL FIBER COMPOSITE OVERVIEW
Technological developments related to the demand and expectations of consumers continue to increase rapidly within global resource, which leads to the main issues of the availability of materials and sustainability of natural resources. Since a few decades ago, natural fiber composite have undergone a remarkable development locally and globally. Non-renewable resource such as petroleum, which is depleting and non-environmentally friendly have made natural fiber more important with its wide range of properties.
Plants for natural fiber are classified into two categories depending on its utilization, i.e. primary and secondary. Primary plants are those grown only for their fiber content such as jute, hemp, kenaf and sisal. Whereas secondary plant fibers are produced as a secondary product such as from pineapple, coir and oil palm. There are several types of natural fiber which are bast, leaf, seed, core, grass and reeds, and other types of fibers. Bast fibers are from jute, flax, hemp, ramie, palm and kenaf.
Leaf fibers are from abaca, sisal and pineapple. Seed fibers are from coir, cotton, palm and kapok. Core fibers are from kenaf, hemp and jute. Grass and reed fibers are from wheat, corn and rice. Lastly, other types of fibers are from wood and roots (Faruk, Bledzki, Fink, & Sain, 2012).
From an engineering point of view, these natural fibers are accepted due their alternative properties compared to conventional synthetic fibers. Natural fibers have high specific properties such as stiffness, flexibility, impact resistance, and modulus.
Furthermore, they are also available in large quantities, renewable, biodegradable, and
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have low cost of production. Natural fibers also offer specific properties such as low density, less equipment abrasion, less skin and respiratory hazard, vibration damping and enhanced impact energy resistance. However its hydrophilicity causes moisture absorption that corresponding to a weak adhesive ability to hydrophobic matrices, this requiring special treatment for enhanced performance of reinforced natural fiber composite (Sgriccia et al., 2008).
The natural hydrophilicity of natural fibers dictates the final properties of composites and can be treated to improve the adhesion capability to matrix materials.
Another challenge to overcome is the natural fibers low degradation temperature, i.e.
around 200 0C, which make it incompatible with thermosets which have high curing temperatures, thus limiting them to low temperature applications. Other important limitations are the low ultimate strength compared to conventional fibers, low elongation properties, large variability of mechanical properties which make them unstable for performance prediction and poor resistance to weathering (Sgriccia et al., 2008).
The reasons for replacing non-renewable resources are due to their unsustainability and society awareness, thus leading to the support of the renewable resources. The automotive industry has moved towards natural resources and have started using natural fibers such as flax-sisal fiber mat with an epoxy matrix to produce door panels for Mercedes Benz E-class, and flax fiber reinforced polypropylene for rear shelf trim panels of the 2000 model Chevrolet impala. Other than the automotive industry, natural fiber composite can also be found in construction in ceiling, panels, and partition boards (John & Thomas, 2008). Thus, the transition towards renewable, sustainable natural living plant fibers with petroleum
