Top hat stiffeners: A study on keel failures

The need to assess the structural capability of curved marine composite structures that support the keel of high performance yachts has increased due to the rise in the number of accidents and human casualties. The top hat stiffener is the basic structural member of the yacht to sustain the tensile and bending load of the keel. This paper characterises the mechanical strength of E-glass/vinylester composite top hat stiffeners subjected to transverse loading. The out-of-plane load transfer was studied and failure modes were identified for the three different composite layups which were tested to failure. Experimental results obtained from mechanical testing were compared with FEA predictions, based on the quadratic interlaminar stress criterion. Secondary reserve strength from the unidirectional fibres was identified and the potential to use this secondary strength was further investigated.