Fatigue crack propagation in composites with spherical fillers—part 1

A study of the effect of various percentages of a spherical filler in a brittle matrix resin on fatigue crack propagation rates was carried out. The resin was a low‐molecular‐weight [ Mn ‐8200; Mw / Mn = 2.04] Bisphenol A‐terephthalate/isophthalate thernmoplastic copolyester. The fly ash filler had a mean diameter of 20μ. Experiments were done with 10 to 40 wt.% filler compliance method. A paris law model fits the data for the unfilled and the 10 wt.% filled compositions. At higher percentages of filler, however, a pattern of increasing and decreasing crack growth rates is observed. The pattern is unique for a given specimen. A mechanism is proposed to explain this behavior.