Fatigue behaviour of glass bead filled epoxy

Abstract

There is a relatively abundant literature on the mechanical properties of particle filled thermosets. Detailed experimental data are available on the effect of variables, such as the filler volume fraction, its surface treatment or shape factor, on the usual properties. In the case of epoxy matrix composites, data have been published on elastic properties. Kinetic studies on thermoplastics, as well as microscopic investigations clearly show that each particle acts as a crack initiation site. The present study deals with thermoset epoxy-glass bead composites. A noticeable advantage of the sphericity of the glass beads over the previously studied mineral fillers is that theoretical calculations, for instance of interparticle average distance, are easier. Some results are reported concerning the eventual role of the geometrical characteristics, including particle diameter, number of particles per volume unit, particle-matrix contact area, interparticle distance, on the fatigue characteristics of the composite as assessed from Paris or Wöhler plots. In addition, quasi-static crack propagation characteristics will be compared with dynamic ones. It is clearly shown that glass beads improved the fatigue crack propagation. Despite this fact, it is also shown that even a small amount of mineral filler, acting as crack initiator, can considerably reduce the fatigue life of epoxy composites.