High temperature deformation studies on CVD silicon carbide fibers

The composite structure of SiC fibers produced by chemical vapor deposition is reviewed briefly in order to illustrate the complex mechanical behavior which such fibers can exhibit. A new apparatus for studying the creep behavior of fibers is described in which virtually isothermal gage lengths can be achieved at temperatures up to 1600 C. A second apparatus for measuring complex dynamic moduli from 0.1 to 25 Hz for temperatures to 1600 C is also presented. Loss (imaginary) modulus values greater than 1 part in 2000 of the storage (real) modulus can be measured. Example data are presented for a variety of loading histories, temperatures and stress levels. A new algorithm for the correction of non isothermal mechanical data is used to compute isothermal dynamic moduli values to 1600 C. It is found that anelastic processes occur both dynamically and in creep at temperatures as low as 1100 C. Activation energies for dynamic loss mechanisms are presented.