Time dependent fatigue crack growth behavior of silica particle reinforced epoxy resin composite

• Fatigue crack growth behavior of the silica particle reinforced epoxy resin composite is Kmax controlled regardless of stress ratio.
• The fatigue crack growth behavior is found to be time dependent based on the Kmax constant fatigue tests with various stress ratios and frequencies.
• The fatigue crack mainly propagates in the resin matrix even along the interface between matrix and particle.

The fatigue crack growth behavior in a silica particle reinforced epoxy resin composite was investigated under two levels of constant Kmax with various stress ratios R and frequencies, where the ranges of R and frequency were from 0.05 to 0.7 and from 0.1 to 10 Hz, respectively. The crack growth rate da/dt under a constant Kmax was almost constant regardless of R and frequency, which clearly confirmed that the crack growth behavior of the present epoxy resin composite was Kmax-controlled and time-dependent. The crack path and fracture surface observations revealed that the crack propagated mostly in the matrix: even for the crack propagation along the boundary between silica particle and matrix, the crack propagated in the matrix near the boundary.