ABAQUS/XFEM to study the fracture of 3D printed polymers considering layer interfaces

Additive manufacturing (or 3D printing) is being increasingly used in a wide range of areas including civil, aerospace and biomedical engineering where it offers significant advantages over conventional methods for model prototyping. However, the reduced fracture resistance typically observed in 3D printed materials limits its application to functional components. The fracture of 3D printed polymer materials with various layer orientations is studied using the extended finite element method (XFEM) with the aid of finite element software ABAQUS. Single edge notch bend (SENB) specimens made of acrylonitrile-butadiene-styrene (ABS) materials through fused deposition modeling (FDM) with various crack tip/layer orientations subjected to 3-point bending are considered. The XFEM with cohesive segment approach is employed to model the inter-laminar fracture (fracture between layers), cross-laminar fracture (fracture through layers), as well as mixed cross-/inter-laminar fracture of 3D printed ABS specimens. Both elastic and elastic-plastic fracture models are developed for the inter-laminar and cross-laminar fracture, respectively. For mixed cross-/inter laminar fracture, an anisotropic damage model is developed to predict the kinked crack propagation patterns as well as the dependence of fracture toughness on crack tip/layer orientations observed experimentally. Two damage initiation criteria were defined considering both the weak interfaces between layers and the maximum principle stress in the determination of the alternate crack growth paths. The anisotropic damage model developed in ABAQUS/XFEM through user-defined damage initiation subroutine is able to capture the fracture behavior of 3D printed polymer materials considering various layer orientations.