Fatigue driven delamination in composite structures: Definition and assessment of a novel fracture mechanics based computational tool

The development of numerical methodologies to investigate material damages is a crucial aspect of aerospace components design. The advent of composite materials has made this aspect more critical due to their anisotropic properties, which result in damage mechanisms difficult to control and predict. Despite the progress made in the development of computational approaches for composites failure assessment, fatigue damage remains an open issue. This work deals with the development of a robust and efficient computational tool to simulate the fatigue driven delamination in complex composite structures. The main objective is to exploit the peculiarities, in terms of mesh and load step size independency, of the well-established SMart-time XB procedure, based on the Virtual Crack Closure Technique approach, to develop a Paris Law-based module to mimic the delamination growth rate due to cyclic loads. The implemented fatigue block interacts with the already existing modules, thus simulating the fatigue driven delamination without mesh dependency and potentially accounting for the R-curve behaviour of the material. The procedure takes advantage of the solver of the commercial Finite Element code Ansys Mechanical but is fully implemented in the Ansys Parametric Design Language, resulting in an absolutely versatile and parametric procedure. The promoted numerical tool has been firstly validated at coupon level considering the literature available Single Leg Bending-based benchmark. Then, the post-buckling behaviour of a typical aeronautical stiffened panel, based on a literature experimental test, has been studied under non-constant cyclic load conditions. Comparison against literature numerical and experimental data have proved the efficiency of the proposed computational tool to simulate fatigue-driven delamination both at coupon level and in complex structures.This work deals with the development of a robust and efficient computational tool to simulate the fatigue driven delamination in complex composite structures. The main objective is to exploit mesh and load independency peculiarities of the well-established SMart-time XB procedure, to develop a Paris Law-based module to mimic the delamination growth due to cyclic loads. The procedure is fully implemented in the Ansys Parametric Design Language, resulting in a versatile and parametric procedure. The promoted tool has been firstly validated at coupon level. Then, the post-buckling behaviour of a stiffened panel, based on a literature experimental test, has been investigated.