X-FEM (eXtended Finite Element Method) is one of the many capabilities offered by Abaqus for detailed modelling of failure in structural components. Available in Abaqus v6.9 and later, the approach allows the simulation of multiple propagating cracks without the meshing requirements of conventional methods. There is no need for mesh refinement at the crack tip or remeshing around a growing crack. The presence of discontinuities is ensured by special enriched functions and additional degrees of freedom.
X-FEM is particularly suited to modelling failure in composite structures. It allows many cracks to propagate in arbitrary directions, avoiding a heavy remeshing process. An example is the simulation of crack propagation in an aircraft component. The complexity and the size of such a structural model does not allow sufficient mesh refinement to enable the traditional approaches to be used. X-FEM enables the user to identify the critical parts of the composite structure. With no mesh dependency, the location of the crack is only function of the material and design parameters.
For a more refined analysis, Abaqus/Standard provides the user with the capability to specify user defined failure criteria which can distinguish between the different failure modes of the composite material. X-FEM enables the simulation of matrix crack propagation as well as brittle fibre failure in tension and the fibre kinking in compression.