Nylon fatigue crack propagation

Effect of Moisture on Fatigue Crack Propagation in Nylon 66... 

Fatigue crack propagation tests were performed on 73-nmi x 73-mm (2.9 in. x 2.9 in.) compact-tension specimens that had been machined from the plaques and then precracked. An electrohydrau-lic closed-loop test machine was used to produce a constant-amplitude, 10-Hz sinusoidal load. Host of the tests were performed in duplicate at room temperature in laboratory air at an average ambient RH of A0%. In view of the slow rate of moisture equilibration in air at room temperature (15), the difference between the ambient RH and that of the nylon being tested was presumed to be unimportant within the time period of the test (3-5 hr). 

Study) are confirmed (or revised) by this more extensive study of the effects of water on fatigue crack propagation In nylon 66 ... 

Bretz, P.E., Effect of Moisture on Fatigue Crack Propagation in Nylon 66, in Water in Polymers, S.P. Rowland, Editor. 1980, American Chemical Society Washington, D. C. p. 531-554. 

Figure 11.26 The relationship between AK and fatigue crack growth rates for poly(methyl methacrylate), PMMA polysulfone, PSF polystyrene, PS polyfvinyl chloride), PVC poly(2,6-dimethyl-1,4-phenylene oxide), PPO polycarbonate, PC nylon 66 and polyfvinylidene fluoride), PVp2 (49). Samples with data to the right are more fatigue resistant than on the left, because they require higher levels of stress at the crack tip to propagate the crack.

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