Active composites utilizing thermal deformation due to reinforcement fibers embedded into metal matrix have been proposed. The deformation behavior of SiC fiber reinforced-nickel matrix composite has been investigated to ensure the reliability of actuation at elevated temperature. It was demonstrated that curvature of the composite non-linearly changed during heating/cooling process. This hysteresis behavior seems to be attributable to the microfracture of composite such as delamination of fiber/sheet interface and failure of fibers. In this study, thermal deformation process of this composite was evaluated by laser AE technique. This composite showed thermal Keiser effect, that is, thermal stresses in the composite cause microfracture in the thermal deformation. The shape of the specimen at room temperature recovered to the previous one below 873 K and became unrecoverable over this temperature. As the result of wavelet analysis of AE signals, sources of AE were clearly classified into two types of microfractures, delamination at fiber/matrix interfaces and crack in matrix.

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