抄録
The impact fatigue tests were conducted on several kinds of laminates such as non-woven polyester cloth or glass cloth reinforced epoxy resins. From the experiments, the properties of impact fatigue strength for these laminates were clarified, and the scatter properties of these strengths were statistically analyzed. The safety factor and the allowable stress for laminates under service impact loadings were studied on the basis of failure probability theory. The results were as follows:
(1) The fatigue strength (σt, τs) of the laminates subjected to repeated impact tensile or shear loads show the scatters of logarithmic distribution and can be estimated as the probability values by the following formula, respectively,
σtNfmt=Dtμsu, τsNfms=Dsμsu
where (mt, Dt), (ms, Ds) are the parameters of impact fatigue properties, Nf is the life to failure, (μ, s) are statistical values and u is the parameter of probability.
(2) Both strength constants (Dt, Ds) are closely related to the static monotonic strength (σB, τf) and can be estimated from these values.
(3) The safety factor and the allowable stress of these laminates under service impact loads can be determined according to the expectative failure probability. It is very useful for the fittest structural design.
