Simulation of non-linear viscoelastic behavior of cross-linked mesoporous silica aerogels by depth-sensing indentation

Abstract

Aerogels are ultra-lightweight nanoporous materials with high thermal insulation value for industrial applications. Recently, a reinforcing process referred to as 'crosslinking' has been implemented to improve their mechanical properties via coating the pore structure with a nano-thin conformal polymer layer. In this study, ordered mesoporous, monolithic silica aerogels obtained by templating with a tri-block co-polymer used as surfactant, is tested by depth-sensing indentation at the room temperature, and the results are compared with simulations using the ABAQUS software package. Assuming that polymer crosslinked aerogels have non-linear viscoelastic properties due to their polymer encapsulated mesoporous structure, the Burgers model is implemented as a user-defined subroutine in the ABAQUS environment. The results clearly show that the loading-unloading curves obtained from the nanoindentation tests are in good agreements with simulation. Therefore, predictions using different loads and loading rates can be modeled by implementing Burger's model.