Hi-Nicalon/SiC minicomposites with (pyrocarbon/SiC)(n) nanoscale multilayered interphases

SiC/SiC minicomposites that comprise different pyrocarbon/silicon carbide ( (PyC/SiC)(n)) multilayered interphases and a tow of SIC fibers (Hi-Nicalon) have been prepared via pressure-pulsed chemical vapor infiltration. Pyroca rbon and SIC were deposited from propane and a CH3SiCl3/H-2 mixture, respec tively. The microstructure of the interphases:has been investigated using t ransmission electron microscopy. The mechanical tensile behavior of the min icomposites at room temperature exhibits the classical features of tough co mposites, regardless of the characteristics of the (PyC/SiC) sequences. The interfacial shear stress has been determined from the width of hysteresis loops upon unloading/reloading and from the crack-spacing distance at satur ation. All the experimental data indicate that the strength of the fiber/in terphase interfaces is rather weak (similar to 50 MPa).