Modeling the plasticity of various material classes with a single quadratic yield function

In this paper, a general quadratic yield function is discussed, which was originally proposed by Chen et al for fiber-reinforced composites [1]. Its applicability to plastically deformable foams, honeycombs, and CFRP (carbon fiberreinforced plastic) is shown. For isotropic elastic-plastic foams it is proven, that the ellipsoid model is a special case of Chen's quadratic yield function, and the according plasticity coefficients are determined analytically. The applicability to aluminum honeycombs is demonstrated by simulation of 4-point bending tests of sandwich structures. Both analytical and experimental procedures are utilized for the derivation of the plasticity coefficients of the honeycomb core. Hypervelocity impact tests on CFRP and numerical simulations are presented as validation of the modeling approach to this kind of material. Finally, suggestions are given for further developments of the plasticity model that could overcome existing limitations.