Fig xA Comparison of through the thickness thermal diffusivity
Fig. 11. Comparison of thermal expansion behaviors of 2D woven and 3D braided composites by CVI process.Figure optionsDownload full-size imageDownload as PowerPoint slide
Thermal diffusivity AR-M 1896 another key parameter for SiCf/SiC composites because thermal stress exists when temperature differs. The thermal diffusivity of both composites decreased at the same rate with increasing temperature due to phonon scattering (Fig. 12). The thermal diffusivity of 3D-braided composite was higher with maximum diffusivity of 6.68±0.4 mm2/s at 35 °C and a minimum of 3.44±0.2 mm2/s observed at 700 °C. Comparatively, the myofibrils diffusivity for 2D-woven SiCf/SiC composite was about 20–30% lower ranging from 5.41±0.1 mm2/s at 35 °C to 2.64±0.1 mm2/s at 700 °C. We believe the predominantly unidirectional fiber orientation in 3D-braided SiCf/SiC composite allowed for better heat flow through the composite. 3D-braided composite exhibited higher variability than 2D-woven composite, which may be the result of more complicated and random networks of pore space in the material.