Multi-scale simulation of the tensile properties of fiber-reinforced silica aerogel composites

A new multi-scale model is proposed to investigate the relationship between the mechanical properties and microstructure of fiber-reinforced silica aerogel composites. The multi-scale model consists of the aerogel model in nanometers and the composite model in micrometers. The aerogel model is generated to represent the cluster structure of silica aerogels based on a modified diffusion-limited cluster aggregation (DLCA) algorithm, in which the size-dependent interactions between the primary particles are obtained from theoretical derivations. A continuum damage constitutive model is established to represent the behavior of the silica aerogel matrix in the composite by implementing the aerogel model with the discrete element method (DEM). After that, a modified embedded element technique (EET) is proposed to generate the finite element (FE) model of the silica aerogel composite with curve fibers. This multi-scale model is used to investigate the tensile behavior of fiber-reinforced silica aerogel composites, while a comparison with experimental results is presented. The numerical results show that the primary particle size has a significant effect on the Young׳s modulus and the tensile strength of the composites. Moreover, our present model is employed to explore the relationship between the mechanical properties of the composite and the fiber characteristics, including the fiber volume fraction, length and curvature. The predictions indicate that the characteristics of the reinforcing fibers are significant for the mechanical properties of silica aerogel composites. The present multi-scale model can be extended to study the mechanical properties of other aerogel composites.