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COMMERCIAL FIBERS. Distribution of Strength. Glass Fibers. E : E lectric C : C hemical S : High S trength. Molecular Structure of Glass. Amorphous Non-crystalline. Process of Spinning Glass Fibers. Carbon and Graphite Fibers. Process to Manufacture Carbon Fibers.
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Glass Fibers E : Electric C : Chemical S : High Strength
Molecular Structure of Glass Amorphous Non-crystalline
Characteristics of Aramid Fiber • glass transition temperature 360C • can be used at 300C for a limited time • low CTE (-410-6K-1) • low electrical and thermal conductivity, high thermal capacity
Reinforcement – Matrix Interface • Strong interface ― high strength & stiffness, low resistance to fracture • Weak interface ― low strength & stiffness, high resistance to fracture Wettability ― the extent to which a liquid will spread over a solid surface Lotus Effect
Surface Tension By 1st law of thermodynamics: Work done = Increment in free energy Where γ= free energy per unit area of liquid – gas interface = force per unit length = surface tension
Spreading Coefficient The necessary condition for spreading of the liquid Define spreading coefficient wetting occurs no wetting is possible
Example of wetting prediction Example: liquid: epoxy Solids: alumina polyethylene epoxy – alumina: wetting is possible! epoxy – polyethylene: No wetting is possible!
LG SG SL Contact Angle By force equilibrium (at the stop liquid front on solid)
Mechanisms of Interfacial Bonding • mechanical bonding : surface roughness ― interlocking or keying normal compression force ― thermal contraction
Mechanisms of Interfacial Bonding • Electrostatic bonding : coulombic force ― short range of interaction • Chemical bonding : secondary bonding
Mechanisms of Interfacial Bonding • Chemical bonding : secondary bonding
Mechanisms of Interfacial Bonding • Reaction or interdiffusion bonding : polymers― intertwining of molecules ceramics― interphase metals― intermetallic compounds
Methods for measuring bond strength • Single Fiber Test
Methods for measuring bond strength • Bulk specimen tests • Three-point bend - short-beam bend test interlaminar shear strength (ILSS) test • Iosipescu shear test
Methods for measuring bond strength • Micro-indentation test
Methods for measuring bond strength • Microbond Test
Methods for measuring bond strength • Microbond Test