This paper describes the influence of vacuum and water environments on the tensile fracture behavior of three different types of ceramic precursor type fibers : one was an oxide ceramic fiber, γ-Al
2O
3 fiber, or Altex
[○!R] fiber manufactured by Sumitomo Chemicals, and the others were SiC fiber, or Nicalon
[○!R] by Nippon Carbon and Si-C-Ti-O fiber, or Tyranno
[○!R], by Ube Industries. Single fiber tensile tests were conducted in air, in vacuum (2×10
-4 Pa for Altex and 4-5×10
-3 Pa for Nicalon and Tyranno), and in deionized water. The tests were conducted at room temperature. The longitudinal elastic modulus of the fibers were independent of testing environment. However, the fiber strength in vacuum was the highest, irrespective of fiber, and it decreased in the order of in air and in water. Moreover, the strength in water decreased with a decrease in displacement rate : the fiber strength decreased with increasing water content in an environment, and with decreasing displacement (strain) rate. The fiber surface damage that caused a decrease in fiber strength could not be observed by high-resolution, field emission type scanning electron microscopy, because the resolution in z-direction was insufficient. In contrast with this, the AFM has nanometric resolution, and the fiber surface damage caused by synergistic effects of water and tensile loading could be identified, and the degradation and fracture mechanisms of the fibers were discussed.
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