Micromechanics of oil palm mesocarp fibres and biocomposites

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(1)UNIVERSITI PUTRA MALAYSIA MICROMECHANICS OF OIL PALM MESOCARP FIBRES AND BIOCOMPOSITES. SUHAIZA HANIM BINTI HANIPAH. FK 2018 66.

(2) PM. U. MICROMECHANICS OF OIL PALM MESOCARP FIBRES AND BIOCOMPOSITES. By. ©. C. O. P. SUHAIZA HANIM BINTI HANIPAH. Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in Fulfillment of the Requirements for the Degree of Doctor of Philosophy. July 2018 i.

(3) COPYRIGHT. ©. C. O. P. U. Copyright © Universiti Putra Malaysia. PM. All material contained within the thesis, including without limitation text, logos, icons, photographs, and all other artwork, is copyright material of Universiti Putra Malaysia unless otherwise stated. Use may be made of any material contained within the thesis for non-commercial purposes from the copyright holder. Commercial use of material may only be made with the express, prior, written permission of Universiti Putra Malaysia.. i.

(4) DEDICATION. Dedicated to my family. ©. C. O. P. U. PM. for their endless love, support and encouragement. i.

(5) Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfillment of the requirement for the degree of Doctor of Philosophy. PM. MICROMECHANICS OF OIL PALM MESOCARP FIBRES AND BIOCOMPOSITES. By. July 2018. Chairman Faculty. : Mohd Afandi P Mohammed, PhD : Engineering. O. P. Investigation was conducted on non-linear mechanical behaviour of oil palm mesocarp fibres (OPMF) and their biocomposites, with focus on the interface of the fibres (filler) and matrix. Viscoelastic with damage was observed from tensile tests conducted under cyclic mode, as reported from the unloadingreloading results of the cyclic tests at larger deformations (2 and 3mm deformation). This behaviour was related to the lignocellulosic components of the fibres, as well as geometry of the fibres consisting of silica bodies and cellular structure. On the other hand, mechanical tests comparison of the processed fibres mentioned before with fresh mesocarp fibres showed different viscoelastic behaviour of the latter fibres, which was due to moisture within the fibres containing palm oil, as well as the effect of oil palm processing that altered the processed fibres. The tests results were modelled through a viscoelastic model available in finite element software, Abaqus, which consisted of hyperelastic model with Prony series and a stress softening function. Good agreement was reported from the fitting of the model to the mechanical tests results, highlighting the viscoelastic behaviour of oil palm fibres. Emphasis was then given to the effect of silica bodies towards integrity of the oil palm fibres, where a cohesive zone modelling (CZM) was included to model the interface between silica bodies and fibres. The results showed minimal effect of silica bodies towards integrity of the fibres as a whole, which was due to the silica bodies were only partly embedded on the outer surface of the fibres. The fibres were then used for biocomposites development as filler, and LLDPE was used as matrix. The interface between the filler and. C ©. U. SUHAIZA HANIM BINTI HANIPAH. i.

(6) ©. C. O. P. U. PM. matrix was improved using anhydrate (maleic anhydride and itaconic anhdride). In addition to the interface improvement using chemical method (anhydrate to strengthen the filler-matrix interface), it is hypothesised that the geometric effect of the fibres consisting of silica bodies on the surface can also improve the filler-matrix interface. Therefore, the fibres were not chemically treated (with alkali or acid as conducted before in previous literatures) to preserve the silica bodies and fibres integrity. Improvement of the biocomposites with both anhydrate and silica bodies was reported from a series of experiments, namely mechanical tests, FTIR, and microscopy analyses. In particular, SEM image showed that silica bodies left craters after being pull during tensile testing, suggesting that the silica bodies prevent sliding between the filler-matrix interface. Likewise, evidence of OH bond between the silica bodies and matrix was shown, similar to the filler-matrix improvement due to addition of anhydrate. Biocomposites finite element model geometry was generated using Digimat software, but the modelling analysis was terminated before any results can be obtained. The results from both mechanical behaviour of fibres and biocomposites interface highlighted that oil palm mesocarp fibres behaved as a viscoelastic material with damage due to deformation, and the fibres used for biocomposites application can be obtained directly without chemical treatment.. ii.

(7) Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk ijazah Doktor Falsafah. PM. MIKROMEKANIK GENTIAN MESOKAP KELAPA SAWIT DAN BIOKOMPOSIT. Oleh. Julai 2018. Pengerusi Fakulti. : Mohd Afandi P. Mohammed, PhD : Kejuruteraan. O. P. Penyelidikan ini dijalankan terhadap tingkah laku mekanikal bukan linear gentian mesokarpa kelapa sawit (OPMF) dan biokomposit, dengan tumpuan pada antara muka gentian (pengisi) dan matriks. Kerosakan viskoelastik ini diperhatikan dari ujian tegangan yang dijalankan di bawah mod kitaran, seperti yang dilaporkan dari keputusan pemuatan semula, ujian kitaran berubah bentuk kepada yang lebih besar (ubah bentuk 2 dan 3mm). Tingkah laku ini berkaitan dengan komponen lignoselulosik serat, serta geometri serat yang terdiri daripada badan-badan silika dan struktur selular. Sebaliknya, perbandingan ujian mekanikal gentian yang diproses yang disebut sebelum ini dengan gentian mesokarp segar menunjukkan kelakuan viskoelastik yang berbeza daripada serat kedua, yang disebabkan oleh kelembapan dalam serat yang mengandungi minyak kelapa sawit, serta kesan pemprosesan kelapa sawit yang mengubah keadaan gentian yang diproses. Keputusan ujian dimodelkan melalui model viskoelastik yang terdapat dalam perisian unsur terhingga, “Abaqus”, yang terdiri daripada model hiperelastik dengan siri “Prony” dan fungsi pelekapan tekanan. Keseragaman keputusan telah dilaporkan dari melalui model kepada hasil ujian mekanikal, menonjolkan kelakuan viskoelastik gentian kelapa sawit. Penekanan kemudiannya diberikan kepada kesan badan silika ke arah integriti gentian mesokarpa kelapa sawit, di mana pemodelan zon kelekatan (CZM) dimasukkan untuk memodelkan antara badan silika dan gentian. Hasilnya menunjukkan kesan minima badan silika terhadap integriti serat secara keseluruhan, yang disebabkan oleh badan-badan silika hanya sebahagiannya tertanam di permukaan luar serat. Gentian kemudian digunakan untuk pembangunan. C ©. U. SUHAIZA HANIM BINTI HANIPAH. iii.

(8) ©. C. O. P. U. PM. biokomposit sebagai pengisi, dan polietilin linear kurang tumpat (LLDPE) digunakan sebagai matriks. Antara muka antara pengisi dan matriks dipertingkatkan menggunakan anhidrat (malik anhadrida dan itakonik anhadrida). Selain penambahbaikan antara muka dengan menggunakan kaedah kimia (anhidrat digunakan untuk menguatkan antara muka pengisimatriks), hipotesis bahawa kesan geometrik gentian yang terdiri daripada badan-badan silika di atas permukaan juga boleh meningkatkan kekuatan antara muka-matriks dan pengisi. Oleh itu, serat tidak dirawat secara kimia (dengan alkali atau asid seperti yang dilakukan sebelum dalam literatur terdahulu) untuk mengekalkan badan silika dan integriti serat. Peningkatan biokomposit dengan kedua-dua badan anhidrat dan silika dilaporkan dari satu siri eksperimen, iaitu ujian mekanikal, transformasi Fourier inframerah, dan analisis mikroskopi. Secara khususnya, imej pengimbasan mikroscop elektron menunjukkan bahawa badan-badan silika meninggalkan kawah selepas di tarik semasa ujian tegangan, mengimplikasikan bahawa badanbadan silika mencegah gelongsor antara antara muka dan matriks pengisi. Begitu juga, keterangan mengenai ikatan hidroksil di antara badan-badan silika dan matriks ditunjukkan, sama dengan peningkatan pengisi-matriks kerana penambahan anhidrat. Model geometri biokomposit melalui elemen tak terhingga dihasilkan dengan menggunakan perisian “Digimat”, tetapi analisis pemodelan telah ditamatkan sebelum sebarang keputusan boleh diperolehi. Hasil dari kedua-dua tingkah laku mekanikal serat dan biokomposit antara muka menyerlahkan bahawa gentian kelapa sawit mesokarpa berkelakuan sebagai bahan viskoelastik dengan kerosakan akibat ubah bentuk, dan gentian yang digunakan untuk aplikasi biokomposit dapat diperoleh secara langsung tanpa rawatan kimia.. iv.

(9) ACKNOWLEDGEMENTS. PM. Alhamdulillah thanks a lot to Merciful Allah for giving me the strength to finish this project. It is hard to find words to express my deepest appreciation to my main supervisor and supervisory committee Dr Mohd Afandi P Mohammed, Dr. Azhari Samsu Baharuddin, Dr Azwani Shah Mat Lazim and Dr. Jaafar Abdullah for their guidance, advice and encouragement throughout my studies. I also gratefully thanked to the financial support by Ministry of Higher Education, Malaysia and Universiti Teknology Mara.. U. I humbly thank you to all the laboratory staff in Faculty of Engineering; Mr Mohd Zahiruddin , Puan Siti Hajar and Mr. Raman Morat. A special thanks to all members of Bioprocess Research Group for their sharing joyful moment with me.. On top of that, to my parents, husband, Noor Hasrell Hassan and family, thank you for the faith, understanding and encouragement until the end and always standing by me through thick and thin. Acknowledgement is also due to those who are involved directly and indirectly in the completion of this study.. ©. C. O. P. Thank You. v.

(10) © O. C. U. PM.

(11) This thesis was submitted to the Senate of the Universiti Putra Malaysia and has been accepted as fulfillment of the requirement for the degree of Doctor of Philosophy. The members of the Supervisory Committee were as follows:. U. Azhari bin Samsu Baharuddin, PhD Senior Lecturer Faculty of Engineering Universiti Putra Malaysia (Member). PM. Mohd Afandi bin P Mohammed, PhD Senior Lecturer Faculty of Engineering Universiti Putra Malaysia. (Chairman). Azwani Shah bin Mat Lazim, PhD Associate Professor Faculty of Science and Technology Universiti Kebangsaan Malaysia (Member). C. O. P. Jaafar bin Abdullah, PhD Senior Researcher Nuclear Agency of Malaysia Malaysia (Member). ©. ROBIAH BINTI YUNUS, PhD Professor and Dean School of Graduate Studies Universiti Putra Malaysia. Date:. vii.

(12) Declaration by graduate student. U. PM. I hereby confirm that: x this thesis is my original work; x quotations, illustrations and citations have been duly referenced; x this thesis has not been submitted previously or concurrently for any other degree at any institutions; x intellectual property from the thesis and copyright of thesis are fullyowned by Universiti Putra Malaysia, as according to the Universiti Putra Malaysia (Research) Rules 2012; x written permission must be obtained from supervisor and the office of Deputy Vice-Chancellor (Research and innovation) before thesis is published (in the form of written, printed or in electronic form) including books, journals, modules, proceedings, popular writings, seminar papers, manuscripts, posters, reports, lecture notes, learning modules or any other materials as stated in the Universiti Putra Malaysia (Research) Rules 2012; x there is no plagiarism or data falsification/fabrication in the thesis, and scholarly integrity is upheld as according to the Universiti Putra Malaysia (Graduate Studies) Rules 2003 (Revision 2012-2013) and the Universiti Putra Malaysia (Research) Rules 2012. The thesis has undergone plagiarism detection software. Signature:. Date:. ©. C. O. P. Name and Matric No: Suhaiza Hanim Binti Hanipah, GS 38212. viii.

(13) Declaration by Members of Supervisory Committee. PM. This is to confirm that: x the research conducted and the writing of this thesis was under our supervision; x supervision responsibilities as stated in the Universiti Putra Malaysia (Graduate Studies) Rules 2003 (Revision 2012-2013) were adhered to.. U. Signature: Name of Chairman of Supervisory Dr. Mohd Afandi bin P Mohammed Committee:. Dr. Azhari bin Samsu Baharuddin. Signature: Name of Member of Supervisory Committee:. Associate Professor Dr. Azwani Shah bin Mat Lazim. O. P. Signature: Name of Member of Supervisory Committee:. Dr. Jaafar bin Abdullah. ©. C. Signature: Name of Member of Supervisory Committee:. ix.

(14) TABLE OF CONTENTS. Page i iii v vi viii xiii xiv xviii xx. U. PM. ABSTRACT ABSTRAK ACKNOWLEDGEMENTS APPROVAL DECLARATION LIST OF TABLES LIST OF FIGURES LIST OF ABBREVIATIONS LIST OF SYMBOLS. CHAPTER 1 INTRODUCTION 1.1 Overview of oil palm mesocarp fibre mechanics and bio composite 1.2 Problem Statements 1.3 Research Objectives 1.4 Research scope 1.5 Thesis Outline LITERATURE REVIEW 2.1 Oil palm in Malaysia 2.2 Oil Palm Fibres Mechanics 2.2.1 Oil palm fibres biomass 2.2.2 Oil palm fibre composition and physico-mechanical properties 2.2.3 Oil palm mesocarp fibres 2.2.3.1 Oil palm mesocarp fiber lignocellulosic characteristics 2.2.3.2 Silica bodies on OPMF surface 2.2.3.3 Mechanical behaviour of oil palm mesocarp fiber 2.3 Oil palm mesocarp fibre biocomposites 2.3.1 Modification of natural fibres 2.3.2 Grafting of biocomposites 2.3.2.1 Types of polymers for biocomposites 2.3.2.2 Grafting process parameters 2.3.3 Research progress on natural fibres biocomposites 2.3.4 Characterisation of OPMF bio composite. ©. C. O. P. 2. x. 1 1 2 2 3 3 5 5 6 6 6 8 11 12 14 16 16 18 19 20 24 26.

(15) 41 41 41. RESULTS AND DISCUSSION 4.1 Micromechanics study of OPMF 4.1.1 Experimental study of oil palm mecocarp fibres (OPMF) 4.1.1.1 Morphological study of OPMF vascular bundle 4.1.1.2 Lignocellulosic content. 55 55. P O C ©. 4. 28 28 29 29 30 36 37. GENERAL MATERIALS AND METHODS 3.1 Materials and methods 3.1.1 Oil palm mesocarp fibres preparation 3.1.2 Oil palm mesocarp fibre (OPMF)-biocomposites preparation 3.1.2.1 Filler and matrix 3.1.2.2 Chemical preparation 3.1.2.3 Formulation parameters 3.1.2.4 Composite pre blending preparation 3.1.2.5 Preparation of moulded sheet 3.2 Experimental methods 3.2.1 Lignocellulosic contents 3.2.2 Oil content analysis 3.2.3 Fibre size distribution 3.2.4 Fourier transform infrared (FTIR) analysis & Thermogravimetric analysis (TGA) 3.2.5 Scanning electron microscopy 3.2.6 X-ray microtomography 3.2.7 Mechanical tests on oil palm mesocarp fibres 3.2.7.1 Tensile tests 3.2.7.2 Cyclic loading and stress relaxation tests 3.2.8 Biocomposites testing 3.2.8.1 Reaction product purification 3.2.8.2 Chemical titration 3.2.8.3 Biocomposites tensile testing 3.3 Development of finite element model 3.3.1 2D micromechanical model development 3.3.1.1 3D micromechanical model development. U. 3. Finite element models for natural fibres and biocomposites 2.4.1 Representative micromechanics model 2.4.2 Linear elasticity 2.4.3 Hyperelasticity 2.4.4 Viscoelasticity 2.4.5 Continuum Damage Model (Mullin’s effect) 2.4.6 Cohesive Zone Model (contact damage model). PM. 2.4. xi. 42 42 43 43 44 44 45 45 46 46. 47 47 47 48 48 48 49 49 49 50 51 51 54. 56 56 58.

(16) CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE WORK 5.1 Conclusions 5.1.1 Micromechanics studies of OPMF (based on objective (a) and (b)) 5.1.2 Studies of OPMF bio composites (based on objective (c) and (d)) 5.2 Recommendations for future work 5.2.1 Micromechanics studies of OPMF 5.2.2 Studies of OPMF bio composites. O. P. 5. 58 59 62 65 66 70 72 72 73. PM. U. 4.2. 4.1.1.3 Oil content analysis 4.1.2 Tensile tests of OPMF 4.1.2.1 Comparison between processed OPMF and fresh fiber OPMF 4.1.3 Model development 4.1.3.1 2D micromechanical modelling results 4.1.3.2 3D micromechanical modelling results Micromechanics study of OPMF biocomposite 4.2.1 Fibres size distribution 4.2.1.1 Morphological and μCT analyses 4.2.1.2 FTIR and Thermogravimetric analysis (TGA) 4.2.1.3 Degree of grafting (DOG) 4.2.2 Biocomposite mechanical testing 4.2.2.1 Effect of silica bodies on mechanical testing 4.2.2.2 Effect of grafting on biocomposites mechanical behaviour 4.2.3 Biocomposites modelling 4.2.3.1 2D biocomposite modelling results 4.2.3.2 3D biocomposite modelling results. 77 79 80 80. 81 84 84 90. 92 92 92 92 93 93 94 95 106 108 109. ©. C. REFERENCES APPENDICES BIODATA OF STUDENT LIST OF PUBLICATIONS. xii.

(17) LIST OF TABLES. Table. Page. 2.1. Physico-mechanical properties of OPF. 2.2. List of grafting modification. 2.3. Band position for grafted functionalities. 3.1. Formulation of OPMF bio composites. 4.1. Values of cellulose, hemicellulose and lignin composition of OPMF. 58. 4.2. Tensile test results of processed OPMF at different speeds. 60. 4.3. The average value from tensile test of fresh OPMF at different speed. 62. 4.4. The viscoelastic model parameters to model OPMF fibres. 65. 4.5. CZM parameters used to simulate debonding between silica bodies and fibre interface. 67. Material parameters used in the constitutive material modelling of OPMF. 84. PM. 25 27. 44. U. ©. C. O. P. 4.6. 8. xiii.

(18) LIST OF FIGURES. Figure. Page Thesis outline. 4. 2.1. Segmentation of oil palm biomass residues. 6. 2.2. Oil palm tree. 2.3. Cross sectional of an oil palm fruit bunch. 2.4. Schematic on typical stages involve to obtain EFB, POME, CPO and OPMF. PM. 1.1. 7. U. 7. Average input and output from the oil palm mill. 10. 2.6. Multi cellular fibre (F) portion called “lacuna” (L). 11. 2.7. Plant cell wall structures. 11. 2.8. Lignocellulosic compound structures. 12. 2.9. Silica bodies’ pathway proposed by Law et al. (2007). 13. 2.10. Polymerization of monomeric salicylic acid. 13. 2.11. Types of Mullins effects. 15. 2.12. Description stress relaxation test. 16. P. 2.5. Method of natural fibre modification. 17. 2.14. Reaction mechanism of MAH onto polyethylene. 24. 2.15. Schematic drawing of interface theory (a) adsorption and bonding, (b) electrostatic attraction and (c) mechanical interlocking. 26. 2.16. A cut out image represent the embedded cell geometry. 28. 2.17. Sample of different arrangement of unit cell model. The boundary areas for unit cell model and the boundary condition under uniaxial tension. 29. Differences between elastic, plastic and viscoelastic. 31. O. 2.13. C ©. 9. 2.18. xiv.

(19) Differences between (a) relaxation and (b) creep test. 32. 2.20. The Prony series representation (Mohammed et al., 2012). 33. 2.21. Damage between the filler ant matrix in the unit cell model a) debonding, b) crack in the particle; and c) void in the matrix. 37. Different damage opening modes a) Mode I (normal), b) Mode II (shear mode) and c) mode III (out of plane mode). 38. 2.23. Traction versus separation curve. 39. 3.1. Oil palm mesocarp single strand fibre. 3.2. Diameter measurement on OPMF fibre. 3.3. Microtomography (Skyscan 1172). 3.4. Sample set up for mechanical test. 49. 3.5. Model development of (a) 2D particle model with clustered arrangement, (b) 2D single particle model with spike and, (c) 3D single particle model. 52. 4.1. Different interactions in OPMF bio-composites systems. 55. 4.2. SEM morphology of : silica bodies on the surface of OPMF (a-b), (c) spiked observed from silica body, (d) craters from dislodged silica bodies at the fractured region, (e) longitudinal crosssectional view of OPMF and (f) diameter cross-section of OPMF after tensile test. 57. U. Tensile test at different speed of 0.1, 1 and 10 mm/s. O. 4.3. 41. P. 2.22. PM. 2.19. Stress relaxation test results at different deformation of 1 mm, 2 mm and 3 mm. C. 4.4. ©. 4.5. 42 47. 59 60. Cyclic test under different deformations of 1 mm, 2 mm and 3 mm. 61. 4.6. (a) Stress relaxation and (b) permanent set illustration. 63. 4.7. Comparison of relaxation stress between empty mesocarp (OPMF) and fresh mesocarp fibres. 64. Comparison of permanent set (from cyclic test) between empty mesocarp (OPMF) and fresh mesocarp fibres. 64. 4.8. xv.

(20) 4.11. 4.12. 66. (a) Comparison between no-debond and with debond (CZM activated) for the 2D models (speed of 1 mm/s) and (b) Stress relaxation simulations result using linear elastic and viscoelastic model for 2D models. 68. PM. 4.10. Fitting of the viscoelastic model (mentioned in Section 2.4.4) to stress relaxation test result at 1 mm deformation using parameters in Table 4.4. (a) CZM parameters sensitivity results for the 2D models simulations (speeds 1 mm/s): (a) parametric study under case 1 (constant Gc = 1 kN/m), and (b) case study under case study 2 (constant ࢚࢔૙ = 100 MPa) 3D finite element results under different matrix thickness (speed 1 mm/s): (a) Perfect silica body and fibre interface and (b) results with CZM activated using parameters in Table 4.5. 71. Stress relaxation simulation using linear elastic and viscoelastic model for 3D model. 72. 4.14. OPMF diameter through laser diffraction microscopy. 73. 4.15. SEM morphological of (a) OPMF composites with 10 wt % loading, and (b) OPMF with 60 wt % loading. 73. SEM morphological of (a-b) OPMF-b-LLDPE composite; (c-d) OPMF-g-LLDPE composite. 74. Schematic image of OPMF-matrix interface. 75. 4.13. 4.16. P. 4.17. SEM morphological show craters formed on LLPDE after tensile test. O. 4.18. Figure of μ-CT slices image (a) at 0 mm height, (b) at 2.50 mm height, (c) at 5.0 mm height and (d) at 7.50 mm height. C. 4.19 4.20. ©. 69. U. 4.9. 4.21 4.22. 75 76. Area fraction of 10 wt% of fibre loading at difference sample height. 77. FTIR absorbance of raw OPMF, OPMG-g-LLDPE and OPMF-bLLDPE. 78. Thermogram (DTA and DTG) of OPMF-b-LLDPE, OPMF-gLLDPE and raw OPMF. 79. xvi.

(21) 4.25 4.26. 4.27. 4.28. 4.29 4.30. Graph of tensile strength of various OPMF percent weight loading. 81. Modification scheme for esterification reaction between OPMF and LLDPE, (OPMF-g-LLDPE). 83. 2D finite element models to investigate the effect of filler, matrix and silica bodies for bio composite application. The model under different cases represents different contact interfaces. 85. (a) Boundary conditions defined for the Case 2 and (b) an example of Case 2 simulation results at 0.53 s (simulation time), where the scale is von Mises stress (MPa). 86. Simulation results of (a) under different contact cases, (b) different fibre contacts, (c) comparison between silica body with and without spikes and (d) different coefficients of friction (for case 1). 86. Different percentages of silica body attachment on fibre (a-c) and (d) silica body with spikes. 87. (a) Finite element model geometry with 60% filler volume fraction (uniform filler) and (b) simulation results at 1.5 s (simulation time), where the scale is Von Mises stress (105 Pa). 89. Simulation results of: (a) single particle and multi particles models using different volume fractions, (b) different matrix elastic moduli and (c) uniform vs non- uniform filler. 90. 3D finite element models geometry at 10% and 20% volume fraction. 91. P. 4.31. 80. PM. 4.24. Degree of grafting of treated and untreated OPMF on different weight loading. U. 4.23. ©. C. O. 4.32. xvii.

(22) LIST OF ABBREVIATIONS. ADL. Acid detergent lignin. BPO. Benzoyl peroxide. CPO. Crude palm oil. CZM. Cohesive zone modelling. DCP. Dicumyl peroxide. DMF. Dimethylformamide. EFB. Empty fruit bunch. FFB. Fresh fruit bunch. HDPE. High density polyethylene. LLDPE. Linear low density polyethylene. LLDPE-g-UT. LLDPE graft Untreated. LLDPE-g-T. LLDPE graft Treated. MAH. Maleic anhydride. MAPP. Maleic anhydride polypropylene. O. MDI. U. Methylene diphenyl isocyanate. NDF. Neutral detergent fibre. OPEFB. Oil palm empty fruit bunch. OPF. Oil palm fibre. OPMF. Oil palm mesocarp fibre. OPMF-b-LLDPE. OPMF blend LLDPE. OPMF-g-LLDPE. OPMF graft LLDPE. PE. Polyethylene. C ©. PM. Acid detergent fibre. P. ADF. xviii.

(23) PP. Polypropylene. RVE. Representative elementary volume. SiO2. Silica dioxide (silica body). Si-O-C. Silica-oxygen-carbon linkages. TGA. Thermogravimetric analysis. PM. Palm oil mill effluent. ©. C. O. P. U. POME. xix.

(24) LIST OF SYMBOLS. Descriptions. σ. MPa. true stress. ε. mm/mm. true strain. E. dimensionless. Young’s modulus. λm. dimensionless. locking stretch. μ. dimensionless. instantaneous initial shear. a. dimensionless. global interaction parameter. W. J. Strain energy potential. g (t). dimensionless. step strain loading in function of time. gi. dimensionless. Constant. g∞. dimensionless. Constant. Gi. dimensionless. Modulus of ith spring. Go. Pa. Instantaneous modulus. G∞. dimensionless. Modulus of infinite lone spring. Gc. J/m2. Energy release rate. t. U. Traction separation vector. t. s. time. s. s. time. Po. MPa. True stress. ξi. dimensionless. Relaxation time constant. η. dimensionless. Damage variable. ௠ ܷௗ௘௩. dimensionless. Deviatoric part of strain energy. O. MPa. C ©. PM. Unit. P. Symbol. xx.

(25) dimensionless. Nominal traction stress vector. K. dimensionless. Tensor coefficient. δ. dimensionless. Separation vector. ©. C. O. P. U. PM. n. xxi.

(26) CHAPTER 1 1 1.1. INTRODUCTION. Overview of oil palm mesocarp fibre mechanics and bio composite. U. PM. Malaysia has been recognised as the second largest producer of palm oil products such as oil palm, olein, stearin and other derivatives in the world (Sabil et al., 2013). With such a huge development, residual materials from the industry become an environmental issue. In palm oil processing, three types of side-products are produced, mainly oil palm empty fruit bunch, oil palm mesocarp fibre and oil palm trunk fibres. Numerous scientific works on empty fruit bunch and palm fibres (mixture of oil palm empty fruit bunch and oil palm stalk fibres) have been extensively reported (Gunawan et al., 2009; Isroi et al., 2012; Law et al., 2007). Nevertheless, to the best our knowledge, very few research works on the mechanics of oil palm mesocarp fibres (OPMF) has been reported. In principle, OPMF is obtained after milling process of oil palm fruit bunches in an oil palm mill. In natural, all fibres are cellulosic material containing cellulose, hemicellulose and lignin. However, detailed investigation of the mechanics of oil palm fibres bundle is not yet available, such as complex mechanical behavior under different loading conditions.. ©. C. O. P. Oil palm fibre usually was used for biocomposites (Shinoj et al., 2011; Rozman et al., 2003; Then et al., 2015) and biocomposting (Nordin et al., 2012; Mohammed et al., 2013). The former application focusses on the creation of new material with intention on superior mechanical strength, while in the latter application, works were conducted on finding the best biological method in production of the compost, as well as the quality of composts produced. The recent study on biodegradation of oil palm fibres by Omar et al. (2017) suggested the importance of studying mechanics of oil palm fibres, especially towards understanding the effect of microbial activity towards volume reduction of fibre from biodegradation process. For oil palm mesocarp fibres biocomposites, the interaction between fibre and matrix, fibre and protrusion (silica bodies) as well as the non-linear mechanics of fibre are very important in order to further understand the mechanics of oil palm biocomposites system. For the fibre – matrix interface, improvement of the interface need to be considered, for example the use grafting process to improve the fibre(filler)-matrix interface using anhydrate chemicals. In addition, the effect of fibre’s outer geometry (such as silica bodies) which can acts as a sliding-prevention mechanism between the fibre-matrix under deformation is important and not yet clearly studied. Thus this research will. 1.

(27) focus with the study of fibre-silica body-matrix interface, in addition to the nonlinear mechanical behavior of oil palm mesocarp fibres. 1.2. Problem Statements. U. PM. There are only a few literatures available on the complex mechanical behavior of OPMF (for example only one study on viscoelasticity of oil plam fibres by Sreekala et al. 2001). The complex mechanical behaviour in this case can referred to as viscoelastic and damage within the fibres due to deformation, this can be due to the lignocellulosic contents of the oil palm fibres, as well as complex geometry of the fibre containing silica bodies partly embedded on the surface and cellular structure within the cross section. Understanding these complex behaviour and microsctructure of oil palm fibres is important for biocomposites application, where it was reported that the fibres need to undergo chemical treatment before they are suitable for composites production. This chemical treatment can alter the mechanical behaviour of the fibres, causing inferior mechanical behaviour of the biocomposites produced. In addition, the interface between oil palm fibres (filler) and matrix need to be investigated, where the behaviour at the interface can be influenced by chemical interaction between filler-matrix and/or geometric effect (silica bodies on the surface). 1.3. Research Objectives. To investigate the non-linear mechanical behavior of oil palm mesocarp fibres (empty fibres and fresh fibres), namely viscoelastic as well as damage due to deformation through complex mechanical tests (tensile, cyclic-tensile and tensile-relaxation modes). To simulate oil palm mesocarp fibres deformation using a finite element viscoelastic model with a damage function, which is developed using information from the complex mechanical tests in previous objective. To produce the bio-composite material using oil palm mesocarp fibres as filler and LLDPE as matrix, where the behaviour of the filler-matrix interface is studied using chemical methods (grafting) and fibre geometric effect (silica bodies).. O. (a). P. Based on the problems statement mentioned before, the following objectives are considered to embark this research project:. ©. C. (b). (c). 2.

(28) (d). 1.4. To simulate oil palm biocomposites interface behaviour using a finite element model, which focusses on the filler-matrix interface and silica bodies effect. Research scope. U. PM. The research scope of this work focusses on the mechanical behaviour of oil palm mesocarp fibres, and mechanics of oil palm fibres biocomposites interface. The former will involve complex mechanical characterisation and micromechanical modelling of oil palm fibres. The mechanical characterization will consider tensile tests under constant speed, cyclic tensile and tensile-relaxation modes. These tests will reveal viscoelastic behaviour of the fibres, with possibility of damage occurring within the fibres due to deformation. The biocomposites study on the other hand involves production of bio composites using in situ grafting method in internal mixer, which includes anhydride, polymer (LLDPE) and OPMF itself. Focus will be placed on the interfacial behaviour of the filler-matrix interface in terms of chemical bonding (from grafting) and microstructural effect (silica bodies effect on preventing filler-matrix sliding). 1.5. Thesis Outline. ©. C. O. P. This thesis is organized into five chapters (Figure 1.1). The introduction and objectives are stated in Chapter 1, whilst the Chapter 2 deals with literature review on the oil palm fibres mechanical behaviour and their biocomposites application. In Chapter 3, the general material and methods involved in mechanical testing of the oil palm fibres and their biocomposites are explained in detail. Likewise, the procedures involved in the finite element model development is discussed in detail in this chapter. Chapter 4 showed experimental results of the oil palm fibres mechanical tests and microscopy analyses, as well as their biocomposites mechanical, chemical and microscopy (x-ray micro-tomography) analyses. This then proceeds with modelling results for the oil palm fibres and biocomposites. Conclusions and recommendations for further work are presented in Chapter 6.. 3.

(29) CHAPTER 2 LITERATURE REVIEW. U. CHAPTER 3 GENERAL MATERIALS AND METHODS. PM. CHAPTER 1 INTRODUCTION. CHAPTER 4 RESULTS & DISCUSSIONS -. ©. C. O. P. -. Experimental study of mechanical behavior of OPMF Development of the oil palm mesocarp fibres mechanical behavior model using finite element method Experimental study of bio-composites of oil palm mesocarp fibres trough improvement of the filler fibre–matrix. Development of the model of the biocomposites behavior for future engineering applications. -. CHAPTER 5 CONCLUSIONS & RECOMMENDATIONS. Figure 1.1 : Thesis outline. 4.

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