Modeling and Simulation

Abstract

Development of theoretical models is very important for syntactic foams. Numerous parameters are involved in syntactic foam design, which include matrix and particle material, particle volume fraction and wall thickness, and reinforcement material and volume fraction. To identify the parameters that would result in syntactic foam with desired set of mechanical and thermal properties, theoretical models can be very useful and cut down the need for experimentation. Several existing models applicable to particulate composites can be modified to include the particle wall thickness effect. Multiscale models that can include the nanofibers or particles along with hollow particles are not available yet. It is challenging to model syntactic foams that contain high volume fractions of hollow particle (close to packing limit) because of particle-to-particle interaction effects. Two models are used in this chapter to estimate the properties of multiscale syntactic foams. Both models are applicable to plain syntactic foams containing only hollow particles in matrix. Therefore, semi-empirical approach is adopted and the experimentally measured properties of nanofibers reinforced polymer are assigned to the matrix. The model predictions are validated with experimental results. Finite element analysis is especially illustrative in understanding the behavior of syntactic foams under the applied load. A validated finite element study conducted on a unit cell geometry comprising a hollow particle and a fiber showed that the particle wall thickness plays an important role in determining the stress distribution in microscale reinforced syntactic foam system. For syntactic foams containing thin-walled particles, the location of the maximum von-Mises stress exists within the particle, whereas above a critical wall thickness the location of the maximum stress shifts to the fiber. This pattern illustrates that the location of failure initiation can be tailored in syntactic foams.