In-situ Observation of Fracture Behavior on Nano Structure in NITE SiC/SiC Composite by HVEM

We have been successfully done in situ observation on the sequence of fracture event at the interface of NITE SiC/SiC composite examined by using miniaturized double notched shear specimen for TEM prepared by Focused Ion Beam method. In this study, we used nano-mechanics TEM experimental apparatus to investigate not only microstructure evolution and but also load and displacement curve at once in High Voltage Electron Microscope. Our results summarize as follows. Cracks were initiated at the interface between carbon coating layer on the SiC fiber and SiC matrices, and propagated along the interface. Load drop in the load and displacement curve during in-situ TEM was clearly observed at the crack initiation. The shear strength by using the miniaturized specimen is about ten times higher than that obtained by the standard testing.