Finite Element Predictions of In-Situ 3D X-Ray CT Determined Compression Failure of Uni-Directional Composites

Pultruded composites for wind turbine blades have excellent properties due to the fiber straightness and the consistent material quality. However, the existence of defects can lead to a severe reduction in blade stiffness and strength. In this work, a finite element model is developed, coupled with X–ray computed tomography data from samples subjected to compression, aiming to predict the mechanical properties of unidirectional carbon fiber composites. The structure tensor method is used on the CT data for the estimation of the spatial fiber orientation distribution on a finite element model. Emphasis is on the simulation and prediction of the kink band formation, during the compression loading. A notch was cut into the scanned samples to trigger the kink band formation and included in the model as an extremely low-stiffness material. The composite material is modeled using an elastic-plastic non-linear homogenized composite formulation, including fiber bending effects. The influence of the notch on the kink-band formation is investigated. The formation of the kink band predicted by the FEM is in good agreement with the experimental results.