Mechanical property test of ceramic fiber reinforced silica aerogel composites

Silica aerogel is hopeful used as thermal insulation material in thermal protection system due to its extremely low thermal conductivity and low density. However, the weakness in mechanical properties has limited its application. By adding ceramic fibers, the strength and toughness of silica aerogel are improved obviously without sacrificing much of its thermal conductivities. Basic mechanical experiments including tension, compression and shear tests were carried out at room temperature for ceramic fiber reinforced silica aerogel composites. The compression tests along in-plane direction of the composite fiber layer at 300℃, 600℃ and 900℃ were also conducted, the microstructure of the samples tested at elevated temperature was analyzed by using SEM. The experimental results reveal that the mechanical properties of the ceramic fiber reinforced silica aerogel composites are transverse isotropic. Both the elastic modulus and the ultimate strength of in-plane samples are about over 28 times higher than those of the out-of-plane samples. The composites show asymmetric elastic modulus for tension and compression. The ratios of tensile modulus to corresponding compression modulus along each direction are 1.60, 1.83 and 0.56 for X, Y and Z directions, respectively. The composite keeps shrinking along thickness direction as temperature increases; the largest shrinkage can be 10.8% at 900℃. The compression properties of the composite layer along in-plane direction at elevated temperature get enhanced with increasing temperature.