Ductile fracture of two-dimensional cellular structures

Crack growth initiation and subsequent resistance to propagation are explor ed numerically for regular and irregular hexagonal honeycomb structures mad e from ductile cell wails. The elasto-plastic response of the cell walls is described by a bilinear uniaxial stress-strain law, with fracture of the c ell walls characterised by the fracture energy per unit area. Estimates for the macroscopic toughness and the associated plastic zone shape are derive d analytically on the basis of simple considerations. Crack propagation is simulated numerically by fracturing elements within a finite element model and K-resistance curves are calculated under the assumption of small-scale yielding, The dependence of the crack growth behaviour upon the cell wall m aterial parameters and geometric imperfections of the structure is investig ated.