STRUCTURE PARAMETER OF INTERFACIAL INTERACTION IN Cf/C COMPOSITES AND ITS CHANGE DURING PORE FORMATION PROCESS

Abstract

The C_f/C composite oxidation of polyacrylonitrile-based carbon fibers with a combined carbon matrix at 600°C up to a weight loss of 80 wt% has been investigated. The changes in the open porosity, specific surface area, apparent and true densities of the composite, as well as the ultimate strength and elastic modulus during three-point transverse bending tests have been analyzed. An analytical model for obtaining qualitative and semi-quantitative estimates of the change in integral pore size during oxidation of heterophase materials has been developed. The change in pore size is estimated through the evolution of open porosity P and materials specific surface area S. The model has been validated in the C_f/C composite oxidation study. The composite's mechanical properties dependences on the value of the integral pore size are obtained and analyzed. The structural parameter P/S characterizes the change in the interphase interaction during pores formation and development. It is established that the failure mechanism depends on the value of the parameter P/S and dynamically changes with the oxidation of C_f/C composite. The use of P/S parameter as a criterion for estimation and control of composite materials structural integrity in open systems is proposed.