Mechanical characterisation of multi-layer epoxy resin-carbon fibre pull-wound composite poles

This paper deals with the material design problem and the numerical simulation of the mechanical behavior of multi-layer carbon-epoxy spinnaker poles to be used in racing and in cruise sailing boats. The structural elements, under standard operating conditions, are mainly subjected to compressive eccentric loads for which they are designed, but, due to the very small thickness-to-radius ratio, they can exhibit an undesirable cross sectional loss of ring stiffness, which can seriously compromise their functionality when more complex and variable loads, depending on wind or sea conditions, are present. To avoid damage problems high ring stiffness for the spinnaker poles is then required. The poles under investigation are obtained by pultruding a stack of five unidirectional fiber plies whose inner, outer and central layers are placed with their longitudinal axis parallel to the main axis of the spinnaker pole, while the other two plies exhibit a winding angle. The location of the wound fibers along the wall thickness of the pole, the value of the winding angle and the consequent quantities of fiber in the wrapped layers affect the ring stiffness of the profile so representing significative variables. In the first part of this research study, different laminate lay-ups are considered and, after a series of experimental tests, the one ensuring the maximum ring stiffness is selected. Starting from these preliminary investigations the second part of the study is devoted to the definition of a simplified FE model of the spinnaker pole, strictly based on experimental determination of the material mechanical properties. The model is validated by a comparison between the numerical results and the experimental ones.