Influence of fiber orientation and matrix processing on the tensile and creep performance of Nextel 610 reinforced polymer derived ceramic matrix composites

The tensile and creep performance of two Nextel® 610 (N610) reinforced polymer derived ceramic composites (UMOX™, OXIPOL) is studied up to 1200 °C. Independent of the fiber orientation (±45° or 0°/90°) all samples exhibit a segment where the strain rate was constant. The creep performance in ±45° is matrix dominated and shows a more pronounced primary creep regime, due to changes within the matrix. The following creep regime with a constant strain rate might be attributed to viscous flow of the SiOC within the matrix based on activation energy (283 kJ/mol) and stress exponent (0.6). In 0°/90° orientation the creep and tensile performance is independent of oxidation, but directly influenced by grain structure of the fiber. The coarser and non-uniform microstructure of the fibers in UMOX™ decreases the stationary creep rates and changes the diffusional creep mechanism. The possibility to modify the microstructure of the fiber during the manufacturing process might be used to adjust e.g. the strength and creep stability of these materials related to the desired applications.