陶瓷纤维增强氧化硅气凝胶复合材料力学性能试验

氧化硅气凝胶具有极低的热导率和密度，可作为很好的隔热材料，而脆弱的力学性能限制了其在隔热领域的应用。在不影响隔热效果的前提下，通过复合陶瓷纤维可增加氧化硅气凝胶的强度及韧性。试验探索了陶瓷纤维增强氧化硅气凝胶在室温下的拉伸、压缩和剪切等基本力学性能，分别研究了300℃、600℃和900℃下复合材料纤维铺层面方向的压缩性能，并采用扫描电子显微镜对高温试样微观结构进行了观察分析。结果表明：陶瓷纤维增强氧化硅气凝胶的性能表现出方向性，弹性模量在铺层面内方向与厚度方向的数值最大相差约28倍，强度极限亦然；在室温条件下，复合材料的拉伸和压缩弹性模量不同，X 、Y 和 Z 方向拉伸模量与对应的压缩模量之比分别为1.60、1.83和0.56；高温下复合材料沿厚度方向收缩，收缩量随温度升高而增大，900℃下的最大收缩量可达10.8%；高温下复合材料铺层面内方向压缩性能随温度升高而增强。

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.