Optimal Numerical/Experimental Assessment on GFRP for Wind Turbine Blades in Repairing Process utilizing Photo Polymerizable Resin

Fiber reinforced plastics are drawing significant attention to the renewable energy sectors in terms of their excellent specific strength, modulus and stiffness properties as well as outstanding processability, corrosion, and chemical resistance. Wind turbine blades, which inherent GFRP main bodies, are the representative practice for generating renewable energy. While the wind turbine blades may inevitably be damaged due to the harsh service environments like low temperature, acidic moisture, and intense UV irradiation. Remediations on a damaged wind turbine are indispensable to preserve the integrity, guarantee the strength, and expanse the service life. The photo polymerizable resins are featured by less energy consumption, equipment requirement and curing time compared to conventional thermal polymerizable resins. During this dissertation, the photo polymerizable resins were employed to conduct patch remediation on pre-damaged GFRP specimens. The stress and damage distributions of repaired GFRP specimens were obtained through numerical/experimental assessments to validate the remediation feasibility; properties in low temperature were investigated, which was in consideration of the relative cold service environment; durability of repaired GFRP specimens in long-term UV and acid ageing were evaluated to represent the typical service environments of wind turbine blades.List of Tables iv List of Figures v Abstract x 1. Introduction 1 1.1 Research background 1 1.2 Research objectives 6 1.3 Chapter overview 6 2. Literature Review 8 2.1 Fiber reinforced composite materials 8 2.2 Fabrication techniques of composites 9 2.3 Repair methods of composites 16 3. Experimental and Numerical Analysis of UV repaired GFRP 22 3.1 Introduction 22 3.2 Experimental works 24 3.2.1 Materials 24 3.2.2 Fundamental specimens fabrication and remediation 24 3.2.3 Characterizations 28 3.2.4 Experimental results and discussion 28 3.3 Numerical works 32 3.3.1 Material properties determination 32 3.3.2 Geometry and material properties 36 3.3.3 Intralaminar damage model 40 3.3.4 Interlaminar damage model 42 3.3.5 Simulation results of tensile test 46 3.3.6 Simulation results of bending test 55 3.4 Conclusions 64 4. Effect of Low Temperature Environment on UV repaired GFRP 66 4.1 Introduction 66 4.2 Experimental works 68 4.3 Results and discussion 69 4.3.1 Tensile and bending strength 69 4.3.2 Mold II fracture toughness 74 4.3.3 Interlaminar shear strength 76 4.3.4 Microscopic observations 77 4.4 Conclusion 81 5. Durability of UV repaired GFRP among Acidic Atmosphere 82 5.1 Introduction 82 5.2 Experimental works 84 5.2.1 Materials 84 5.2.2 Fundamental specimens fabrication 85 5.2.3 Specimens remediation and ageing conditioning 85 5.2.4 Characteristics 88 5.3 Results and discussion 89 5.3.1 Tensile and bending strength 89 5.3.2 Mode I fracture toughness 91 5.3.3 Interlaminar shear strength 95 5.3.4 Thermal analysis 96 5.3.5 SEM observations 98 5.4 Conclusions 101 6. Performance of UV repaired GFRP during UV ageing Process 103 6.1 Introduction 103 6.2 Experimental works 105 6.2.1 Materials 105 6.2.2 Specimens remediation and ageing conditioning 105 6.2.3 Characteristics 107 6.3 Results and discussion 108 6.3.1 Tensile and bending strength 108 6.3.2 Mode I fracture toughness 111 6.3.3 Interlaminar shear strength 113 6.3.4 Thermal analysis 114 6.3.5 SEM observations 117 6.4 Conclusions 120 7. Summary and Conclusions 121 Acknowledgements 125 References 126Docto