Influenza dell’interfaccia fibre-matrice nella formulazione di modelli di resistenza macroscopici per materiali compositi

Aim of the work is the definition of domains apt to describe the overall strength properties of composite materials reinforced by long, parallel fibers, with a fiber-matrix interface of finite strength. To this end, a homogenization procedure for periodic media is employed in the framework of limit analysis theory, which allows one to define the macroscopic strength domain, Ghom, according to the known strength domains of the components (fiber, matrix and interface). By formulating suitable microscopic stress fields and failure mechanisms for a representative volume of the composite, inner and outer bounds to Ghom can be defined. Analytical expressions are also derived to approximate the composite strength under particular stress conditions in the case of matrix and interface complying with von Mises or Tresca yield conditions. Finally, further developments are outlined to improve the model and reduce the gap between the obtained bounds.