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 compo sites (C/C; C/SiC and SiC/SiC) with simple (PyC or BN) or complex interphas es [C (B) or (PyC-SiC)(n) multilayers] are fabricated in a short time by CV D/CVI. The fiber/matrix interfacial zone is characterized by AES and TEM. T ensile tests are used to assess the mechanical properties and the Weibull s tatistical parameters of both the fiber and matrix, as well as the fiber-ma trix interfacial parameters (tau(i); t(d); G(ic)). The tensile stress-strai n behaviour has been modelled. The tensile curves exhibit the same features as those previously reported for real no-composites. Lifetime at high temp eratures in air is characterized through static/cyclic fatigue tests and mo delled. It is improved by replacing conventional pyrocarbon by highly engin eered interphases. The micro/mini composite approach is used in the optimiz ation of processing conditions and to derive parameters necessary for the m odelling of the thermomechanical and chemical behaviour of composites with more complex fiber architectures. (C) 1999 Elsevier Science Ltd. All rights reserved.