Effect of SiC coating and heat treatment on damping behavior of C/SiC composites

Three groups of 2D and 3D C/SiC composites were fabricated by chemical vapor infiltration (CVI) process: the first group was as received, the second group was treated at 1500 °C in vacuum atmosphere for 2 h, and the third group was deposited with a chemical-vapor-deposited (CVD) SiC coating. Damping properties of these composites were measured by dynamical mechanical analyzer (DMA) at different frequencies from room temperature to 400 °C in air atmosphere. The results show that SiC coating and heat treatment decrease damping capacity of C/SiC composites and the damping peak disappears or decreases in the testing temperature range. The effect of CVD SiC coating on damping behavior of 2D and 3D C/SiC composites is mainly related to the change of porosity and is independent of fiber preform architecture. However, the effect of heat treatment on damping behavior of 2D and 3D C/SiC composites is mainly attributed to the change in the SiC matrix and interphase bonding, and it is dependent on fiber preform architecture. Both of CVD SiC coating and heat treatment studied in this paper have no influence on relationship between damping behavior of C/SiC composites and frequency.