Influence of strong fiber/coating interfaces on the mechanical behavior and lifetime of Hi-Nicalon/(PyC/SiC)(n)/SiC minicomposites

Hi-Nicalon fiber-reinforced silicon carbide matrix minicomposites (Hi-Nical on/SiC) with nanoscale multilayered (PyC/SIG), fiber coatings (also referre d to as interphases) have been manufactured via pressure pulse chemical vap or infiltration (P-CVI). Fiber/coating interfaces were strengthened by usin g treated fibers. The microstructures of the interphases as well as the pro pagation and deflection of cracks in the interfacial region were investigat ed by SEM and TEM, Interfacial shear stress was estimated using various met hods based on either the width of hysteresis loops on unloading-reloading, crack spacing, or fitting of the force-deformation curve using a micromecha nics-based model. Tensile behavior at room temperature and lifetime in stat ic fatigue in air at 700 degreesC were related to the interphase/interface characteristics.