Ceraset (TM) and Blackglas (TM) mini-tow composites with carbon-coated Nicalon (TM) tows

Abstract

Two commercially available preceramic polymers are the polyureasilazane Ceraset(TM) resin from DuPont Lanxide Composites and the polysiloxane Blackglas(TM) resin from AlliedSignal Inc. The Ceraset(TM) polymer pyrolyzes to a silicon carbonitride under nitrogen and a silicon carbide under argon. The Blackglas(TM) polymer produces a silicon oxycarbide under nitrogen or argon pyrolysis. Two groups of ceramic composites were made with the two preceramic polymer systems and single rows of carbon-coated ceramic grade Nicalon(TM) fiber, using 6 infiltration seeps and 1000°C argon pyrolysis. The mean tensile break loads for the two composite sets were equivalent -75 Newtons with coefficients of variation of 10-20% and obvious fiber pull-out. The break loads were independent of the matrix weight fraction, showing that the fibers are the dominant source of strength. There was no apparent difference in short term oxidation protection between the two types of matrix compositions, given the rapid oxidation of the pyrolytic carbon on the Nicalon(TM) fibers. Oxidation at 1000°C in air for one hour embrittled both sets of ceramic composites, reducing the mean break loads to 27 Newtons.

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