Abstract:The mechanical properties of Sheet Moulding Composite (SMC) have been analyzed by means of static and fatigue tests in tension. SMCs show a substantial in-plane anisotropy either in terms of stiffness or strength. Fatigue data were modeled adopting a fatigue model with two parameters, represented by the cyclic number and the mean stress. The statistical implementation of such model was based on the hypothesis that the monotonic tensile strength follows a twoparameter Weibull distribution. The model has the potential to be predictive indicating that the fatigue characterization of a given laminate can be achieved with a minimum number of experimental tests. The reliability of such procedure and its applicability limits are discussed in the light of the model parameters obtained for different glass fiber reinforced composites.

The reliability of Sheet Moulding Composite (SMC) has been analysed by means of mechanical static and fatigue tests. SMCs showed substantial in-plane anisotropy either in terms of stiffness or strength reflecting the preferential orientation of the short fibres along the direction of the conveyor belt during the processing operations. The static data were modelled on a statistical basis assuming that the monotonic tensile strength follows a two-parameter Weibull distribution, while for the fatigue test we adopted a two parameters model already validated for Glass Fibre Reinforced Plastics (GFRP). Overall, the procedure indicated that he material reliability and its applicability limits can be achieved with a minimum of experimental tests

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The topics considered in this article have been chosen to address the issue of understanding both how polymer composite matrix properties develop during the manufacturing process and the complexity of evaluating the mechanical properties. Representative manufacturing techniques for the production of composite materials are reported and described; this will stand as a necessary overview to identify, among the different manufacturing technique, the common transformation stage to which the resin matrix is subjected, including the dramatic properties change and their complex interaction taking place during the manufacturing process. The relevance of a deep knowledge of thermomechanical matrix properties evolution was then underlined in order to achieve a reliable process modeling. The most used mechanical tests for advanced composite materials are reviewed, showing that the same characteristic property definitions generally used for conventional materials can be identified for these novel materials. In some cases, additional constants are required and some differences in nomenclature are introduced, especially when no isotropic counterpart exists. Representative statistical aspects of static strength and fatigue behavior are also outlined.