VIII
LIST OF FIGURES
• Figure 2.1: Fracture path in composite materials [8] • Figure 2.2: General loading on a cracked body [6] • Figure 2.3: The three fundamental modes of fracture [6] • Figure 2.4: Schematic of the influence of fibre orientation on
delamination initiation [8]
• Figure 2.5: Force vs. time curve during impact
• Figure 2.6: Residual tensile strength vs. impact energy [7]
• Figure 2.7: Parameters that affect the impact resistance of CFRP [14] • Figure 2.8: Relative ranking of the importance of the impact resistance
parameters [14]
• Figure 2.9: Types of stitching used for TTR: a) lock b) modified lock c) chain [6]
• Figure 2.10: Tufting schematic • Figure 2.11: Z-fibre preform
• Figure 2.12: Heat and pressure insertion process [6] • Figure 2.13: Hand held UAZ unit
• Figure 2.14: New gantry currently in use at Cranfield University
• Figure 3.1: Layers of support and base foam ready for the pin insertion • Figure 3.2: Automated machine for pin insertion in the preform
• Figure 3.3: Cutted plies of prepreg ready for the lay up
• Figure 3.4: Toolings used for the manufacture of the I-section • Figura 3.5: Laying up process for an I-section lap joint
IX • Figure 3.6: Heated vacuum table
• Figure 3.7: (a) I-section stacking sequence; (b) Joint geometry • Figure 3.8: Preparation of the laminate stack [6]
• Figure 3.9: Z-pins insertion [6]
• Figure 3.10: Cutting of the excess pin length and foam removal [6] • Figure 3.11: Autoclave
• Figure 3.12: I-joints as they come out from the autoclave • Figure 3.13: I-joints trimmed and ready to be tested • Figure 3.14: Tensile test fixture
• Figure 3.15: Fixtures glued to an end of an I-section • Figure 4.1: 100kN Instron machine
• Figure 4.2: Rosand falling weight impact machine • Figure 4.3: Impact point on the I-section joints
• Figure 4.4: Force vs. time curve during impact of a pinned joint • Figure 4.5: Detail of Z-pinning and modified patch-end design • Figure 5.1: Z-pin reinforcement layout
• Figure 5.2: Failed reinforcement content test I-sections, 2% (far) 4% (near)
• Figure 5.3: 15 mm overlap length, delamination failed I-sections • Figure 5.4: 45 mm overlap length, delamination failed I-sections • Figure 5.5: Laminate failed reinforced overlap length I-sections • Figure 5.6: Load vs. displacement curves for 2% & 4% z-pin content
tests
• Figure 5.7: Ultimate load vs. overlap length plot showing unreinforced patch data
• Figure 5.8: ‘Failure Map’ for reinforced and unreinforced I-section joints
X
• Figure 5.9: SEM micrograph showing Z-pins in failed laminate surface • Figure 5.10: SEM micrograph showing the detail of a single Z-pin
chamfered end
• Figure 5.11: Polished ‘noodle region’ sections on A-A from a typical control joint (top) and a typical Z-pin reinforced joint (bottom)
