Adhesive bonding of fiber laminate patch to sandwich-structured composite

Abstract: By using composites when constructing vehicles, lighter weight and thus better performance can be achieved. Composites are widely used in airplanes and small boats, but has yet to be incorporated in larger ships such as freighters and cruise ships. The main hindrance for its use is the lack of practical knowledge and experience. However, the Visby corvette is a 70 m ship made entirely out of composite and a great proof of concept. The Visby is made by Saab Kockums which also uses composites in many other of their products and continually seeks improvements. One such improvement can be made in joining techniques by attaching composite structures with an adhesive. However, predicting the load bearing capability of adhesive joints proved difficult. Therefore, a literature survey has been carried out to find the most important parameters for the load bearing capability of the adhesively attached patch. After this investigation it was decided that stress concentrations arising in the adhesive joint should be investigated with finite element (FE) methods and confirmed with optical microscope images of patches that had already been mechanically tested. FE modeling succeeded in predicting failure in accordance with the adhesive joints that were modeled. The microscope images confirmed the results from the FE modeling, but also revealed areas of failure in the adhesive joint which could not be predicted with the FE models. Improvements for the FE model were also discussed to facilitate its use when constructing composite structures. A better model would aid in expanding the use of composites and reaping the benefits of those materials.