Multi-axial brittle failure criterion using Weibull stress for open Kelvin cell foams

Foam structures have found an increasingly wide utilization in modern industry because of their porous geometric characteristic and favorable mechanical properties like lightness, high strength and so on. Elastic buckling, plastic yielding, brittle fracture and crushing are typical failure mechanisms of foam structures. The influences of foam geometry and morphology on the failure mechanisms are still not fully understand. In this paper the Kelvin cell model is used to simulate the foam structure and to study the influence of relative density and geometric properties on failure behavior. By extensive FEM analyses of representative volume elements under multi-axial loading with periodic boundary conditions the macroscopic failure limit surface is calculated in stress space. Locally at the microstructure the probabilistic Weibull model and the maximum principal stress criterion are used as failure criterion.