Non-linear behaviour of foam cores and sandwich materials, part 1:: Materials and modelling

The paper develops the modelling used to evaluate the non-linear behaviour of two-dimensional test specimens of foams or foam sandwich materials. The stress-strain curves derived from the different tests carried out on the sandwich constituents are incrementally linearised and the modelling introduces an incremental procedure during which the strain and stress state is evaluated by finite element analysis. At each step of the procedure, the principal strains are calculated in every element of the test specimen under consideration, allowing the compressive or tensile strain and the shear strain to be evaluated. Then, the different moduli of the sandwich constituents are adjusted according to the values of the compressive or tensile strain and of the shear strain. Modelling also considers large deformations and displacements, as well as fracture processes.