Experimental investigation on mechanical properties of a fiber-reinforced silica aerogel composite

Aerogel has been used for thermal insulation because of its extremely low thermal conductivity, but the application has been restricted to non-loading-bearing structures by its low strength properties. Fiber-reinforced aerogel was prepared with higher strength but without sacrificing much of its thermal conductivity. While fiber-reinforced aerogel performs as load-bearing insulation, two behaviors must be investigated: compression and stress relaxation at evaluated temperature. At first, compression test was performed on a fiber-reinforced aerogel composite at both room and evaluated temperature, then the effects of temperature on compression properties of the fiber-reinforced aerogel were analyzed. Stress Relaxation Test was carried out at a constant strain of 0.1 for 1200 s at both room and evaluated temperature. The experimental results show that the stress relaxations increase with the temperature rise from 200 °C to 800 °C. Previous research and Scanning Electron Microscope (SEM) analysis of specimens showed that two time-dependent behaviors: (1) cracks induced by collapse of the pores, and (2) fiber failures subject to interfaces that debond and slide, might be possible reasons for the stress relaxation and the small inelastic strain of specimen tested at 25 °C. While three time dependent phenomena: (1) fusing of aerogel nanoparticles to form nanoparticle clusters, (2) fiber stress relaxation and (3) fiber failures subject to interfaces that debond and slide, would be possible reasons for the remarkable stress relaxation behavior at 800 °C.