Improving the thermal expansion behavior and damping capacity of C/SiC composites by heat treatment

The present study proposes the heat treatment method to optimize the coefficient of thermal expansion (CTE) and damping capacity of 2D C/SiC composites. Results demonstrated that CTE increased monotonically with measuring temperature and could be tuned in a wide range from 2.16 × 10⁻⁶ to 0.48 × 10⁻⁶ K⁻¹ at 200 °C by controlling the HT temperature. CTE decreased significantly at HT temperatures below 1700 °C and remained constant above that value and up to 1900 °C. The damping capacity of C/SiC composites could be improved by increasing HT temperature up to 1700 °C by introduction of thermally-induced microcracking phenomena; thereafter further increase in HT temperature did not contribute to damping. Matrix microcracking due to heat treatment also relaxed the residual stress state of the material by counteracting part of the matrix extension through propagation inside the composites hence contributing to dissipation of imposed vibration energy. A HT temperature value of 1700 °C was identified as critical for the total relaxation of thermal stresses; further increase in HT temperature failed to create more microcracks.