Abstract
This thesis focuses on the subject of damage in composite materials and structures, in particular delaminations arising from an impact event and subsequent Mode I and Mode II loading and fatigue delamination growth. Interlaminar fracture toughness values have been calculated from an experimental study for DCB and ENF specimens. Specimens with artificial inserts at two different interfaces were used along with specimens with delaminations introduced from an impact event. The standard analysis method for both Mode I and Mode II has been adapted to account for the delamination away from the mid plane. For Mode I loading, the load to initiate delamination growth from experimental results is in good agreement with the predicted results from the adapted Mode I equation. For Mode II loading, crack migration did not appear obvious from the experimental study, and an adapted equation accounting for delaminations away from the mid plane has been successfully used. A fatigue study on a structural element loaded both in-plane and out of plane has highlighted the complex nature of damage growth in composite structures. The study has highlighted the issues of delamination investigation using the ultrasonic NDT technique, whereby non-critical delamination growth is sometimes masked by the more dominant delamination and as such the complex growth of delaminations within a structure is difficult to quantify using this technique.