DEFORMATION OF CLOSED-CELL FOAMS INCORPORATING THE EFFECT OF INNER GAS PRESSURE

Abstract

The objective of this work is to numerically investigate the elastic–plastic deformation of closed-cell foams incorporating the effect of inner gas pressure. Both body-centered cubic (BCC) and face-centered cubic (FCC) arrangements of pores are considered in analysis. It is seen that the inner gas pressure has a significant effect on the plastic deformation of closed-cell foams, which is different for the foams with different microstructures and is discussed in detail. The inner gas pressure results in the asymmetry of uniaxial tensile-compressive stress–strain curves and the nominal Poisson's ratio. It is shown that the inner gas pressure makes the yield surface move to the negative direction of the hydrostatic axis in the plane of equivalent and hydrostatic stresses, and the moving distance is equal to the magnitude of inner gas pressure in the foams. Moreover, a new yield function incorporating the effect of inner gas pressure is developed for closed-cell foams. The material constants in the yield function depend on the microstructures of the foams.