IN SITU OBSERVATION ON FRACTURE PROCESS OF SiC_f/Al METAL MATRIX COMPOSITES

The fracture process in the fatigue and tensile test of SiC fiber reinforced aluminum composites was observed in situ with a scanning electron microscope. It is found there exist three stages of damage. The first stage is that the cracks initiate at the stress-concentrated sites caused by fiber fracturing, which increases as the load cycles increase. The second stage is characterized by multi-cracks in each fiber and extension of cracks. The last stage indicates the coalescence of cracks and the formation of a main cracked plane. No fiber-matrix interface debonding was observed during the fracture process. The apparent interfacial bonding strength evaluated in terms of a shear lag model indicates a strong interfacial bonding.