On the flexural fatigue behaviour of glass fibre reinforced nanoclay modified epoxy matrix composites

In the past few decades it has been demonstrated that the properties, specifically the mechanical ones, of thermo-set resins can be modified significantly by means of the addition of small quantities of nanoclay (such as montmorillonite). In particular improvement of the elastic modulus, tensile strength and of the fracture toughness can be obtained, even if a reduction of the ductility is generally recorded. Few works in literature deal with the fatigue behaviour of nano-modified resin systems, but the authors claim a tendency to better performances if compared with the original matrices. On the other hand, fatigue data are nearly not available at all for three phase composites, i.e. fibre reinforced nano-modified matrices. To develop structural applications based on long fibre reinforced composite materials with nano-modified matrix essential aspects are the choice of the type and the percentage of nano-reinforcement in the matrix, together with the definition of techniques for the uniform dispersion of nano-reinforcement in the whole component. Moreover new design criteria, especially as regards fatigue, which take account of the peculiarity of these triphasic materials, are needed. In this work the three point bending fatigue behaviour of a glass woven fabric nanoclay modified epoxy matrix composite produced by infiltration in vacuum bag is experimentally investigated. In order to enhance the differences in matrix properties short composite beams with different layups are tested at low frequency (to reduce the heat generation) on an Instron servo-hydraulic machine. The temperature of the specimen, its stiffness, the crack density in the thickness and the delamination onset and propagation are monitored