The purpose of this study is to investigate the influence of a spatially moving load and edge effects on the fatigue life of the foam-cored sandwich structures. A spatially moving load can be observed in structures subjected to slamming. A new geometry of specimen is developed to reduce the influence of edge effects in the test specimen. Numerical model results of the new geometry are presented. This study confirms that edge effects are leading to early failures and shear stress concentrations are significantly reduced near the edges, improving ASTM C393 standard.

Foam-cored sandwich yacht hulls are subjected to high core shear stresses during slamming events. As slamming is repetitive by nature, failures observed on boats may be due to fatigue. This study aims to investigate possible improvements to fatigue testing of both foam core materials and sandwich specimens. In general test set-up induces differences between the ways a material behaves in a test coupon and in a real application. One such difference is “edge effect”, as the material behaviour can change close to a free edge. For example, the micro-structure may have been affected by the specimen machining, which may influence failure initiation. This is exacerbated if the test set-up induces stress concentrations close to the edge. Another difference is that in a standard core shear fatigue testing by 4 point bending, the stress field is spatially static, when in a slamming event the stress field is spatially variable. Does the material react differently to a static and moving stress field? This study aims to develop a core shear test method replicating a moving stress field, free of edge effect. This paper presents the finding of the initial steps of this study: The edge effect has been investigated using modified loading fixture. The moving stress field has been investigated with a modified 4- point bending test using asynchronous loading. The differences in test results between the modified test methods and the relevant standard test methods indicate that both aspects affect measured fatigue life.

The boat concept of Lutra 80 Singularity was to create a true dual-purpose yacht that rewards its owner with racecourse performance and a high level of interior luxury. The hull form and underwater appendages combined with an aggressive sail plan showed impressive results on the racecourse. This task has required a significant amount of tank and tunnel tests. Not all the planned tests could be carried out within a limited time and with a certain constraint on the budget. This report presents the results of a series of CFD experiments based on the OpenFOAM platform. Marin tank test gave results which were confirmed in the real tests in the sea. The main purpose of our computations at this stage is to reproduce the resistance (drag) curves at various heeling angles. We used different mesh sizes and configurations. In general, we achieved a good correspondence (within 10%) between CFD and Marin tank test results. However this correspondence is not uniform. For more accurate results, it is necessary to apply refinement of the mesh, and continue to search for suitable regularization parameters.