FRP has the nature of visco-elasticity and this has various effects on the mechanical behavior of FRP. In estimating the fatigue life of FRP under random load, the frequency dependence is one of the most important subjects. From this standpoint, investigations were made on the fatigue properties of satin woven glass cloth FRP under six different sinusoidal wave loads at frequencies of 0.1, 1, 5, 10, 15, 20Hz. Both the constant stress amplitude and the programmed loading tests were carried out by a hydraulic fatigue testing machine.
As a result of this paper, it was shown that the fatigue life of FRP is affected strongly by the change in repeated frequency, and the following experimental equation was obtained to represent the S-N relationship for the different repeated frequencies;
σ0.91f+9.79×Nf=100.86f+16.2
where σ is the applied stress, Nf the expected fatigue life and f the repeated frequency, respectively.
The fatigue life under programmed loads at various frequencies could also be estimated to some extent by using the weighted mean of material constants.
