Effects of face sheet damage on residual strength of GRP sandwich panels in naval ships

Extensive studies have been previously carried out on the effects of various types of local damage on the performance of sandwich panels used in the hull structures of naval ships. Recently the approach has been adapted for application on board a specific ship series. Strength reduction data have been obtained for a set of sandwich materials that are representative for the vessels in question. The face sheet materials are glass-reinforced plastics (GRP) with non-crimp fabrics and two different types of vinylester resin. The core materials are PVC foams. Impact damage by sharp and blunt objects is represented by machined cracks and circular holes in the face laminates. Tests have been performed on laminate specimens with and without circular holes under tensile loading and on sandwich face sheets with holes, cracks and real impact damage under compressive loading. The results are compared with available damage models and curves are proposed for representing the reduction in residual strength in the presence of impact damage of varying sizes.