Study On Damping Capacity Of C/SiC Composites

Continuous carbon fiber reinforced silicon carbide ceramic matrix composites (C/SiC) are considered as the most promising thermal structural candidate materials for aerospace, energy and nuclear technologies etc. To minimize the effects of vibration and noise in service environment on the stability of C/SiC components, it's necessary to investigate the damping capacity of C/SiC composites; nevertheless, there have been few reports on this area. Dynamic Mechanical Analysis (DMA) was employed in this thesis to investigate the damping capacity of C/SiC composites fabricated by CVI method, and the damping mechanism of C/SiC composites was discussed. Moreover, the effects of preform dimension coating and heat treatment on the damping peak of C/SiC composites were investigated, and the feasibility to regulate the damping capacity through control the thickness of PyC interphase was explored. The main contents and conclusions are as follows:1. The damping capacity of 2D and 3D C/SiC composites were investigated. It revealed that 2D C/SiC composites have higher damping capacity at the same test frequency. The damping curves of 2D and 3D C/SiC composites have similar change trend in some specifically temperature range.2. The damping mechanism of C/SiC composites was discussed. The main damping mechanism was consisted of the expanding of crack damping of C fiber and PyC interphase. effect of porosity.3. The effects of coating and heat treatment on the damping peak of C/SiC composites were studied. It revealed that CVD SiC coating and 1500℃ heat treatment decrease the value of damping peaks, and the position of damping peaks was changed.4. The damping capacity of 2D C/SiC composites with various thickness PyC interphase was investigated. The result revealed that 2D C/SiC composites will have higher damping capacity if the PyC interphase has a moderate thickness, and thefeasibility to regulate the damping capacity through control the thickness of PyCinterphase was proved.