High performance oxide fibers for metal and ceramic composites

A family of oxide fibers, Nextel (TM) 610 Ceramic Oxide Fiber, Nextel (TM) 720 Ceramic Oxide Fiber and a new fiber, Nextel (TM) 650 Ceramic Oxide Fiber, has been developed specifically for the reinforcement of metal and ceramic matrix composites. This paper summarizes room and high temperature properties for these fibers. The strength of both single filaments and multi-filament rovings of Nextel 610, 650 and 720 fibers was determined between 25 and 250 mm gauge length. Weibull analysis was used to compare the statistical fracture distribution and gauge length dependence of strength. Fiber fracture statistics were in accord with Weibull theory; the effect of diameter variability on the statistical analysis was found to be small. Fractographic analysis on Nextel 610 fiber was used to identify primary fracture-causing defects; defect size was correlated with Griffith fracture predictions. High temperature single filament strength measurements were performed on Nextel 610, 650 and 720 fibers between 800 and 1400 degreesC. High temperature strength varied inversely with strain rate, in combination with tensile creep tests at 1100 and 1200 degreesC, these were used to compare the elevated temperature capability of each fiber and determine maximum use temperatures. The development of crystalline yttrium aluminum garnet fibers that demonstrate further improvements in creep performance relative to Nextel 720 fibers is also discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.