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Characterization of the Thermo-mechancial Behavior of Crosslinked Silica Aerogel

Katti, Atul Ramesh
Silica aerogels are highly porous materials. Applications are limited due to their brittle and hygroscopic nature. In an effort to increase the strength, Leventis developed a method to strengthen aerogels by crosslinking them with isocyanate. DMA tests were conducted on the crosslinked silica aerogel samples revealed two glass transitions, one at 130 oC, indicating the major glass transition and the other at -50 oC indicating the secondary transition. The frequency scan data was shifted horizontally to get the storage modulus data for 25 decades. Nanoindentation tests were performed on CSA samples of various densities and the load depth curves were obtained. From this data the creep compliance curves and subsequently the relaxation moduli were obtained. The Load-depth curves indicate an increasing stiffness with the density. For the split Hopkinson bar tests perfect equilibrium and constant strain rate could not be achieved and hence the results serve only as estimates.