Damage tolerance of an elastic-brittle diamond-celled honeycomb

The fracture strength of an elastic-brittle, centrally cracked plate made from a diamond-celled lattice is calculated by finite element simulations. Conventional linear elastic fracture mechanics applies when the crack length much exceeds the cell size. But when the crack is only a few cell sizes, the stress concentration at the crack tip is negligible and the strength is comparable to the unnotched strength. An analytical model is derived for the fracture toughness.