Evaluation of Elastic Modulus of C/C Composites at High Temperature by Relative Deflection Method

C/C composites are a kind of ideal structural materials used at high temperatures. Their high temperature elastic modulus are very important for the thermal stress analysis and composite structure design. The inductance micrometer can be used to determin the deflection accurately in the three-point bending tests, and the tested results can be used to calculate the elastic modulus at room temperature (RT). However, the application of three-point bending method at high temperature is scarcely reported due to the difficulty of the deformation measurement. In this study, the relative deflection method based on the relative method was used to evaluate the elastic modulus at various temperatures. The measured results of elastic modulus of 2D and 3D C/C composites at RT by inductance micrometer and relative deflection method are similar. The elastic modulus of C/C composites at RT similar to 1700 degrees C was measured by the relative deflection method, and the results show that the maximum of the 2D and 3D C/C composites which appear at 1200 degrees C are 82.22 GPa and 66.73 GPa, respectively. The elastic modulus decreases gradually with the increasing temperature from 1200 degrees C to 1700 degrees C, and the modulus of 2D C/C composites decreases more quickly. These results demonstrate that the C/C composites measurement by the relative deflection method for determining high-temperature elastic modulus is accurate and reliable, which could be used to evaluate the modulus of other high-temperature structural materials.