Non-Contact and Non-deatuctive Measurement of Residual Strength in Fiber-Reinforced ceramic Matrix Composited through Dielectric Properties

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Dielectric properties of various kinds of fiber-reinforced ceramic matrix composites have been measured and the measured dielectric properties are used as an indicator of damage stored in the composites. Experimental set-up, which consists of dielectric lens, horn antenna and high-frequency (20-40 GHz) network analyzer, is prepared for the purpose of damage detection. The set-up allows non-contact and non-damage measurement of the change in dielectric properties due to introduced microfracture events. The relationships between dielectric properties and damage parameter, and, damage parameter and applied tensile load, are obtained and used them as a master curve of the evaluation of stored damage. Through this relation stored unknown tensile damage of SiC fiber-reinforced SiC matrix composites is successfully determined. The procedure is also applied for the evaluation of oxidation damage in SiC fiber-reinforced SiC matrix composite. Similar to the mechanical damage, the change due to oxidation of SiC is clearly detected. Summarizing these set of results, the method is presented as a "non-contact", "non-destructive" detection procedure for ceramic fiber-reinforced ceramic matrix composites.