Anisotropic thermal deformation measurement of aerogel composites based on digital image correlation method

It is important and fundamental to measure the deformations of thermal protection materials and structures under thermal and mechanical loads in the research on their mechanical properties at elevated temperature. A non-contact measuring system based on the digital image correlation method was established to realize the deformation measurement up to 800℃. Thermal deformation measurements in both out-of-plane and in-plane material orientations were conducted for the ceramic fiber reinforced SiO₂ aerogel composites with the reference temperature 25℃ when the composites were heated to different temperatures in the range of 300-800℃. The results show that the deformation measuring method based on this testing system can be used to measure the high temperature deformations of these thermal protection materials. The high temperature thermal deformations of ceramic fiber reinforced SiO₂ aerogel composites are obviously anisotropic. The contraction occurs in the out-of-plane direction while the expansion occurs in the in-plane direction. The main reasons resulting in the thermal deformation anisotropy could be the aggregations of particles in the SiO₂ aerogel matrix and the layered distributed feature of reinforcing fibers in the in-plane direction.