Writing Your Phd Thesis in Microsoft Word
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The Effects of Fibre Moisture Content During Manufacturing on the Properties of Flax/Epoxy Composites A Thesis submitted to The University of Manchester for the Degree of Doctor of Philosophy in The Faculty of Science and Engineering 2020 ABDUL HAKIM ABDULLAH Schools of Natural Sciences Department of Materials 1 Table of Content Table of Content .......................................................................................................... 2 List of Figure ............................................................................................................... 6 List of Tables ............................................................................................................. 12 List of Symbols .......................................................................................................... 14 List of Abbreviations ................................................................................................. 16 Abstract ...................................................................................................................... 18 Declaration ................................................................................................................ 19 Copyright Statement .................................................................................................. 20 Acknowledgement ..................................................................................................... 21 Chapter 1 Introduction .......................................................................................... 22 1.1 Overview ..................................................................................................... 22 1.2 Future of Natural Fibre Based Composites ................................................. 24 1.3 Research Motivation ................................................................................... 25 1.4 Research Objectives .................................................................................... 26 1.5 Thesis Outlines ........................................................................................... 26 Chapter 2 Literature Review ................................................................................. 28 2.1 Natural Fibres ............................................................................................. 28 2.1.1 Flax Fibres and Their Composites ........................................................ 29 2.1.2 Chemical Composition and Internal Structure of Natural Fibre .......... 32 2.1.3 The Origin of Hygroscopic Behaviour in Natural Fibres ..................... 33 2.2 Polymeric Matrices ..................................................................................... 41 2.2.1 Epoxy Resin .......................................................................................... 41 2.2.2 Moisture Contamination in Uncured Epoxy Resin .............................. 43 2.3 Composites Manufacturing ......................................................................... 48 2.4 Ideal Humidity Conditions for Composites Processing and Fabrication .... 49 2.4.1 Moisture Presence during Composites Manufacturing ........................ 50 2.5 Fibre/Matrix Interface Bonding .................................................................. 51 2.5.1 Interfacial Bond Strength Measurement ............................................... 51 2.5.2 Relationship between MC and Interfacial Bond Strength .................... 52 2.5.3 Influence of Fibre Swelling and Shrinkage at the Fibre/Matrix Interface .............................................................................................................. 54 2.5.4 Effect of Chemical Treatment to Increase Interfacial Bonding ............ 55 2.6 Surface treatment to Enhance Natural Fibre Composites Performance ..... 56 2.6.1 Chemical Treatments ............................................................................ 57 2 2.6.2 Silane on Alkalized Fibre Treatment .................................................... 58 2.6.3 Physical Treatments .............................................................................. 59 2.7 Effect of Humidity on Composite Mechanical Performance ...................... 60 2.8 Fracture Toughness and Impact Properties of Composites ........................ 64 2.8.1 Interlaminar Fracture Toughness (ILFT) .............................................. 64 2.8.2 Low Velocity Impact ............................................................................ 66 2.8.3 Compression After Impact (CAI) ......................................................... 68 2.9 Key findings of The Literature ................................................................... 68 Chapter 3 Experimental ......................................................................................... 70 3.1 Materials ..................................................................................................... 70 3.2 Fabric Surface Treatments .......................................................................... 71 3.2.1 Alkaline treatment ................................................................................ 71 3.2.2 Silane Treatment ................................................................................... 71 3.2.3 Alkaline & Silane Treatment ................................................................ 72 3.3 Conditioning Flax Fibres ............................................................................ 72 3.4 Composites Manufacturing ......................................................................... 73 3.5 Sample Cutting and Post-Conditioning ...................................................... 74 3.6 Characterization Methods ........................................................................... 75 3.6.1 Dynamic Vapour Sorption (DVS) Analysis ......................................... 75 3.6.2 Simple Weight Gain Method ................................................................ 75 3.6.3 Crimp Measurements ............................................................................ 77 3.6.4 FTIR-ATR Spectroscopy ...................................................................... 77 3.6.5 Single Fibre Tensile Testing (SFTT) .................................................... 77 3.6.6 Density Measurements ......................................................................... 79 3.6.7 Determination of the Fibre Volume Fraction of Composites ............... 81 3.6.8 Microbond Shear Test Measurements of Fibre-Resin Interfacial Shear Strength (IFSS) ..................................................................................... 81 3.6.9 Dynamic Mechanical Analysis (DMA) ................................................ 84 3.6.10 Tensile Testing ..................................................................................... 85 3.6.11 Flexural Testing .................................................................................... 86 3.6.12 Interlaminar Shear Strength (ILSS) ...................................................... 87 3.6.13 Mode I - Interlaminar Fracture Toughness (ILFT) ............................... 87 3.6.14 Mode II- Interlaminar Fracture Toughness (ILFT) .............................. 91 3.6.15 Low Velocity Impact Testing ............................................................... 92 3.6.16 Ultrasonic C-Scanning Inspection ........................................................ 92 3.6.17 Compression after impact (CAI) Test .................................................. 93 3.6.18 Scanning Electron Microscopy (SEM) ................................................. 93 3 Chapter 4 Results and Discussions ....................................................................... 94 4.1 Characterization of Untreated Flax Fibre ................................................... 94 4.1.1 Moisture Content .................................................................................. 94 4.1.2 Relative Humidity (RH) Sensitivity ..................................................... 95 4.1.3 Graphical Method for Estimating MC of Flax Fabric .......................... 96 4.1.4 Changes of Fibre Density ..................................................................... 98 4.2 Interfacial Shear Strength (IFSS) of Flax/Epoxy Composites .................... 99 4.2.1 Microbond Force-Displacement Curves ............................................... 99 4.2.2 Effect of Embedded Length ................................................................ 101 4.2.3 Interfacial Shear Strength (IFSS) and Weibull Analysis .................... 102 4.3 Mechanical Performance of Untreated Flax/Epoxy Composites .............. 106 4.3.1 Influence of Moisture Content on Fibre Volume Fraction ................. 106 4.3.2 Tensile Properties ............................................................................... 107 4.3.3 Flexural Properties .............................................................................. 111 4.3.4 Interlaminar Shear Strength (ILSS) .................................................... 113 4.3.5 Dynamic Mechanical Analysis (DMA) .............................................. 115 4.3.5 Mode I DCB - Interlaminar Fracture Toughness (ILFT) ................... 120 4.3.6 Mode II ENF - Interlaminar Fracture Toughness (ILFT) ................... 127 4.3.7 Low Velocity Impact .......................................................................... 130 4.3.8 Compression After Impact (CAI) ....................................................... 136 4.4 Mechanism