An in-plane phase-field ductile fracture model for orthotropic paperboard material

A phase -field ductile fracture formulation for orthotropic paperboard materials is proposed, based on an anisotropic, multi -surface elastoplastic model describing the in -plane behavior of paperboard. A variational statement for the finite -step elastoplastic problem is extended to include the variational description of Griffithtype brittle fracture by a phase -field gradient term. The interaction between plastic and fracture dissipation mechanisms is modeled by introducing a scalar modulation function, assuming plasticity driven damage growth. This function depends on a scalar measure of the plastic strain components in the material orthotropy frame. It modifies the fracture activation criterion in a non -variational fashion, resulting in a directiondependent material strength against crack propagation. The model performance is assessed by comparing numerical simulations and experimental tests conducted in a climate -controlled laboratory.