Tensile Tests of Miniature Fiber Reinforced Ceramic Composites for Screening Process-Property Relations

摘要

Mechanical testing of 2-D and 3-D composites in bar geometries is material, time, and cost intensive. As an alternative low-cost, rapid-fabrication geometry, multifilament Nicalon~(?0 (with pyrolytic carbon-coating) tows were densified with the preceramic polymer (Blackglas~(?)) technology to form single tow ceramic "mini-composites". Using modified ASTM tow testing methods, the Blackglas-Nicalon(C) mini-composites were tested in tension at ambient temperatures. The ceramic mini-composites had fibrous failure with linear load-deflection curves and mean breaking loads of 70 N. Gage length (1, 2.5 & 5 c m) effects on breaking loads were minimal. The coefficient of variation (CoV) for the ceramic mini-composites was 19 percent as compared to a 10 percent CoV for earlier tensile tests on Blackglas-Nicalon 2-D fabric composite bars. Results were compared to tensile tests of epoxy-Nicalon tows. Breaking strengths of the ceramic mini-composites were roughly 30 percent of the breaking strengths of the epoxy-Nicalon composites. Oxidation at 600 deg and 1000 deg C for 1 hour embrittled the Blackglas-Nicalon (C) composites and reduced the breaking load to values of 42 N and 17 N, respectively.