| Summary: |
Laminated polymer matrix composite materials are increasingly used in structural applications. However, these materials are susceptible to delaminations. It is well known that delaminations can be particularly dangerous, because they are barely visible and yet may significantly degrade the structural performance. This has motivated a significant number of studies on interlaminar fracture aimed at characterising the delamination resistance, especially under mode I, mode II and mixed mode I-II loadings. While the current state-of-the-art in mode I and mode II interlaminar fracture can be considered satisfactory, further studies are still required on mixed-mode I-II testing. Such studies must address the testing of multidirectional laminates, more representative of structural applications than standard unidirectionals, and the definition of mixed-mode I-II delamination criteria. On the other hand, very few studies have been reported on mode III fracture, an issue that is important to evaluate, since general loadings involve mixed mode I-II-III conditions.
The final goal of the proposed project is precisely the development and validation of delamination criteria of general applicability i.e. mixed-mode I-II-III and various delamination interfaces. This calls for the development of new test methods and for a careful selection of specimen stacking sequences. Considerable difficulties must be tackled, especially the complexity of the stress fields in the vicinity of delaminations between differently oriented plies and the possibility of intraply damage. Therefore, sophisticated modelling techniques will be employed to define the characteristics of the test specimens and to analyse the results. |