Micro/minicomposites: a useful approach to the design and development of non-oxide CMCs

Micro (one single filament) and mini (one single fiber tow) non-oxide composites (C/C; C/SiC and SiC/SiC) with simple (PyC or BN) or complex interphases [C (B) or (PyC-SiC)(n) multilayers] are fabricated in a short time by CVD/CVI. The fiber/matrix interfacial zone is characterized by AES and TEM. Tensile tests are used to assess the mechanical properties and the Weibull statistical parameters of both the fiber and matrix, as well as the fiber-matrix interfacial parameters (tau(i); t(d); G(ic)). The tensile stress-strain behaviour has been modelled. The tensile curves exhibit the same features as those previously reported for real no-composites. Lifetime at high temperatures in air is characterized through static/cyclic fatigue tests and modelled. It is improved by replacing conventional pyrocarbon by highly engineered interphases. The micro/mini composite approach is used in the optimization of processing conditions and to derive parameters necessary for the modelling of the thermomechanical and chemical behaviour of composites with more complex fiber architectures. (C) 1999 Elsevier Science Ltd. All rights reserved.