Failure analysis of composite laminates with a hole by using finite element method

Predicting the strength of a given laminate has been extensively studied. There have been several fracture models proposed but still the immense tests of composite laminates are still needed. Different material systems or lay-ups exhibit different failure modes and failure mechanisms. This thesis focuses in investigation of the failure mechanism of the [+/-theta/0 2]s and [02/+/-theta]s laminates with a hole. ANSYS finite element models with and without a crack in vicinity of hole were developed to investigate the effect of the stress distribution due to the presence of the angle ply crack. The stress concentrations were obtained. It is found that (1) The stress concentrations increases as d/w increases for a given theta in [+/-theta/02] s and [02/+/-theta]s laminates; (2) For a given d/w ratio, the stress concentrations increases as ply orientation, theta increases; and (3) The high stress concentrations on 0° ply occurs at the location where the theta-ply crack intercepts at the line perpendicular to the 0° ply. Based upon the understanding the failure mechanism, a simple expression to estimate the strength of laminates with a hole is established. A strength model based upon the 0° ply load carrying capability is proposed. Prediction is a good agreement with the experimental results.