AN EXPERIMENTAL INVESTIGATION OF DAMAGE EVOLUTION IN A CERAMIC-MATRIX COMPOSITE

The mechanical behavior of a glass-ceramic matrix composite, SiC/CAS (calcium aluminosilicate reinforced with unidirectional SiC fibers), is studied. Results based on uniaxial tension experiments are presented for specimens with fibers aligned in the loading direction. Axial and transverse strain gages on all four gage section surfaces and in situ acoustic emission and ultrasonic wave speed measurements were used to monitor the evolution of damage. All measurements were made with high-resolution, continuous data acquisition. Post-test optical and scanning electron microscopy was also used to identify the various micromechanisms of damage. The experimental results demonstrate the existence of ''zones of deformation'' which are associated with the onset of different damage mechanisms. It is shown that the observed stress-strain behavior can be explained in terms of the material properties of the matrix and the fiber, the material processing, and the postulated zones of deformation.