Materials Modeling

Accurate and computationally efficient predictive models for the effective thermal conductivity of composites are needed to accelerate the design of new materials with improved properties and behavior. The predictive capabilities of previously developed models for particulate composites (PC) apply to limited ranges of component properties and proportions. Furthermore, existing material models that account for particle contiguity and filler-matrix thermal contact resistance fail to distinguish between those two effects. In this work, two novel and complementary predictive models for the effective thermal conductivity of two-phase isotropic particulate composites are derived: (i) a simple yet efficient analytical model for non-contiguous filler particles, and (ii) a generalized semi-analytical model accounting for both filler particle contiguity and thermal resistance at the filler-matrix interface. The latter model is powered by a thermal conduction grid solver algorithm that allows the incorporation of an unlimited number of elements and components to match increasingly complex particulate composite material configurations and behaviors. The two models proposed in this work can match previously published experimental data fairly well. The grid model is further leveraged to relate the effective thermal conductivity to filler particle size and size distribution. It is found that the formation of filler conduction chains is favored by well-graded particle size distributions.

A simple and efficient computational tool modeling the brittle thermal-cracking behavior of a spherical shell encapsulating a round inclusion is presented and compared to existing numerical techniques. Model applications to parametric studies and to particulate composite materials are proposed.

A simple and efficient computational tool modeling the brittle thermal-cracking behavior of a cylindrical shell encapsulating a cylinder inclusion is presented and compared to existing numerical techniques. Model applications to parametric studies and to soundless cracking demolition are proposed.

This paper presents a new constitutive model that unifies the behavioral characterizations of rubber-like materials in a broad range of loading regimes. The proposed model combines a selection of existing components that are known to reflect, with suitable accuracy, two fundamental aspects of rubber behavior in finite strain: (i) rate-independent softening under deformation, also known as the Mullins effect, and (ii) hyper-viscoelasticity, including at high strain rates. The evolution model is further generalized to account for multiple rates of internal dissipation (or material time-scales). Suitable means of identifying the system's parameters from simple uniaxial extension tests are explored. Several aspects of the model's behavior are shown in virtual experiments of uniaxial extension, at different stretch rates. A possible directional approach extending the model to handle softening induced anisotropy is briefly discussed.