6 High Performance Fibers and Fibrous Materials.ppt

High Performance Fibers and Fibrous materials
Yiping Qiu
Donghua University
Outline
Carbon fibers
Glass fibers
Aramid fibers
Ultra High Modulus Polyethylene fibers
Carbon nanotubes
Ceramic fibers
Mechanical properties of fibers
Carbon fibers
Reading assignment
Hull and Clyne, Chapter 2 Fibres and Matrices, An Introduction posite Materials, 2nd ed. Cambridge University Press. Pages 9 –30.
Carbon fibers
Manufacturing processes
Structure and properties
Carbon fibers
Manufacturing processes
Thermal position of anic precursors
Extrusion of pitch
Carbon fiber manufacturing processes
Rayon based carbon fibers
Stabilization at 400°C in O2, depolymerization & aromatization
Carbonization at 400-700°C in an inert atmosphere
Stretch and graphitization at 700-2800°C (improve orientation and increase crystallinity by 30-50%)
Carbon fiber manufacturing processes
PAN (polyarylonitrile) based carbon fibers
PAN fibers
Stabilization at 200-300°C in O2, depolymerization & aromatization, converting thermoplastic PAN to a nonplastic cyclic or pound
Carbonization at 1000-1500°C in an inert atmosphere to get rid of noncarbon elements
Stretch and graphitization at >1800°C, formation of turbostratic structure
Stabilization of PAN fibers
Pitch based carbon fibers
pitch - high molecular weight byproduct of distillation of petroleum
heated >350°C, condensation reaction, formation of mesophase (Liquid crystal): Structure of mesophase pitch
melt spinning into pitch fibers
Oxidation at a temperature below softening temperature
conversion into graphite fibers at ~2000°C without tension
Pitch based carbon fibers
Advantages
Much higher degree of graphitization than polymer based carbon fibers
High strength and modulus
High thermal conductivity: even much better than copper