Effects of loading frequency and environment on delamination fatigue crack growth of CFRP

The delamination fatigue crack growth was investigated with two kinds of unidirectional CF/epoxy laminates. In the T300/3601 laminate, Mode I crack growths in air were cycle dependent, while it was time dependent in water, and the growth rate in water was lower than that in air. Mode II crack propagation rate either in air or in water was also constant with crack extension, and the crack growth was time-dependent. The crack propagation rate in water was faster than that in air, and it increased with prior-immersion period in water. In the M40J/2500 laminate either in air or in water, Mode I delamination fatigue crack growth was cycle-dependent, and the growth rate in water was lower than that in air. Mode II crack propagation rate either in air or in water was almost constant with crack extension, and the crack growth was cycle-dependent. The crack propagation rate in air was almost identical to that in water.