COVER SHEET Title: Simulation of Arbitrary Delamination Growth in Composite Structures Using the Virtual Crack Extension Method

A finite-element-based toolset has been developed to simulate arbitrary evolution of 3-D, geometrically explicit, interlaminar delaminations in composite structures. A new energy-based growth formulation uses the virtual crack extension (VCE) method to predict point-by-point growth along the delamination front. The VCE method offers an accurate and computationally efficient means to extract both energy release rate, , and rate of change of energy release rate, , from a single finite element analysis. A new VCE implementation is used to decouple and compute 3-D, mixed-mode, fracture parameters, permitting the use of mixed-mode growth criteria. The parameters create an influence matrix that relates an extension at one point to the energy release rate elsewhere along the delamination front. The use of the matrix, in conjunction with an iterative approach that continually updates the delamination configuration by re-meshing, enables the prediction of arbitrary delamination evolution. The numerical techniques and formulations implemented allow a delamination to grow by the rules of mechanics and physics, while reducing computational artifacts, e.g. mesh bias. The evolution of an initial embedded elliptical delamination under central point-loads into a circular configuration is simulated as a proof-of-concept for the new growth formulation.