Fatigue crack propagation in composites with spherical fillers‐II effect of the size of the filler

Abstract A study of the effect of spherical glass beads of mean diameters of 46 microns, 89 microns, and 133 microns, on fatigue crack propagation rates, was carried out at ten and thirty weight‐percent beads. The resin was a low‐molecular‐weight [M_n = 8200, (M_wM_n) = 2.04] Bisphenol A‐terephthalate/isophthalate thermoplastic copolyester. Fatigue crack‐grwoth rates were measured using compliance method. The relationship between logarithm of stress intensity factor change and logarithm of crack‐growth rate is linear for 46 micron beads. For the 89 micron beads, the relationship is still approximately linear. The incorporation of 133 micron beads, however, results in large fluctuations in crack‐growth rates with changes in stress intensity factor range. A mechanism is proposed to explain this behavior. A relationship between interparticle distance and fatigue crack‐growth resistance is also observed.