Preliminary study on ductile fracture of imperfect lattice materials

The ductile fracture behavior of two-dimensional imperfect lattice material under dynamic stretching is studied by finite element analyses (FEA). Three isotopic lattice materials, including the regular hexagonal honeycomb, the Kagome lattice and the regular triangular lattice, are taken into account, which are made of an elastic/visco-plastic metal material. Two typical imperfections (vacancy defect and rigid inclusion) are introduced separately. The numerical results reveal novel deformation modes and crack growth patterns in the ductile fracture of lattice material. Various crack growth patterns as defined according to their profiles, such as "X"-type, "Butterfly"-type, "Petal"-type. Crack propagation could induce severe material softening and plastic dissipation of the lattices. Subsequently, the effects of the strain rate, relative density, microstructure topology, and defect type on the crack growth pattern, the associated macroscopic material softening and the knock-down of total plastic dissipation are investigated.