Page 90 - Fiber Fracture

Fiber Fructure
M. Elices and J. Llorca (Editors)
0 2002 Elsevier Science Ltd. All rights reserved

FRACTURE PROCESSES IN FINE SILICON

CARBIDE FIBRES

A.R. Bunsell

Ecole des Mines de Paris, Centre des Math-iawr, B.P. 87, Evty Cedex, France

Introduction ..................................... 76
Spinning of a Polymer Precursor Fibre .................... 76
Cross-Linking of the Precursor Fibre ..................... 77
Oxidation Curing ................................ 77
Radiation Curing ................................ 77
Pyrolysis .................................... 78
Near-Stoichiometric Sic Fibres ........................ 78
FractureMorphologiesof SuccessiveGenerationsof SiCFibres ......... 78
Mechanical Properties and High-Temperature Behaviour ............. 83
Conclusion ..................................... 87
References. ..................................... 87

Abstract

Small diameter silicon-carbide-based fibres have been available since the beginning
of the 1980s and their availability has driven the development of ceramic matrix
composites for structural uses at very high temperatures. Several generations of these
fibres have been produced and the changes in the fracture morphologies between the
generations reveal the modifications which have been made to the fibres so as to improve
their behaviour at high temperature. The fracture surfaces of the first generation fibres,
as seen in the scanning electron microscope, indicated an amorphous microstructure,
whereas those of the latest generation are clearly granular. More detailed analyses by
transmission electron microscopy have revealed the increasingly crystalline nature of
successive generations of these fibres. These changes have led to the production of fibres
which have higher moduli and much improved creep behaviour.

Keywords
Silicon carbide; Fibres; Mechanical properties; Microstructure; Defects