The peculiar SMart-Time XB approach for delamination growth prediction and its evolution towards fatigue investigations

This paper deals with the Smart Time XB (SMXB) procedure, a parametric 3D methodology to simulate the delamination evolution in composite structures. The SMXB method has been developed almost ten years ago and, over time, has been improved with new features to become a forefront method compared with the state of the art. The SMXB is based on the Virtual Crack Closure Technique, which is nowadays implemented in the principal and most used Finite Elements (FE) commercial software. The main peculiarity of the SMXB is its capability to overcome the limits in terms of load step size and elements size dependences typical of the VCCT approach in mimic the delamination propagation. The SMXB procedure has been validated over years considering different structures and load conditions. The last development, which make the SMXB even more complete and attractive, is the ability to simulate the fatigue-driven delamination. Indeed, the Paris Law has been introduced in the core structure of the SMXB to make it able to mimic the delamination evolution under cyclic loading conditions. This manuscript has the intent to describe the theory behind this peculiar procedure and its evolution toward fatigue simulation. An experimental literature Double Cantilever Beam benchmark has been used to prove the robustness and effectiveness of this computational methodology, highlighting its main peculiarities. Single leg bending example, representative of a mixed mode interaction, has also been presented.