The mechanics of open-cell solid foams: Modelling, simulation, and experiment

Despite the practical importance of solid foams, there exist little theoretical modelling, multiaxial test, or whole-field strain measurement of solid foams undergoing large deformations, which are commonly involved in foams' applications. It is the purpose of this thesis to propose a micromechanical model and develop appropriate experimental techniques for Foam Mechanics, which are capable of predicting foam behaviors, testing stress-strain responses, and measuring strain fields under arbitrary deformation modes including multiaxial large deformations.; In this thesis, an energy-based micromechanical model of the open-cell solid foams is formulated for arbitrary deformation modes. This model elucidates the theoretical aspect of foams' heterogeneous deformation patterns invoking the concept of phase transition. It reveals a non-convex elastic energy function for low-density foams. The heterogeneous deformation together with a stress-strain plateau turn out to be a natural consequence of this underlying non-convex elastic energy function, which exhibits a close analogy to au equilibrium phase transition. The stress-strain relations under various deformation modes are simulated through a numerical solution for mechanical equilibrium; In order to meet the requirement for advanced materials test, a new biaxial materials testing system is developed. The technological difficulty faced by all attempts of biaxial tests, i.e. the kinematic incompatibility in loading grips, is resolved through a novel design of comb-like grips.; Conventional strain measurement only provides the overall (averaged) strain, which is insufficient to characterize heterogeneous deformation A whole-field non-contact strain measurement technique, Digital Image Correlation, is also developed. The measurement results reveal the localized deformation patterns and verify our theory.