Influence of Environmental Conditions on the Fatigue Strength of Plastics

In this paper, the effect of environmental conditions, especially humidity, on the fatigue strength of polymers is discussed. Acrylonitrile butadiene styrene (ABS) and acetal homopolymer (POM), which are utilized in industrial applications, were used. The fracture surface was observed by means of scanning electron microscopy (SEM)and the fatigue specimen was quantitatively analyzed with a scanning acoustic microscope (SAM) to clarify the influence of environmental conditions. As a result, it was found that (1) ABS and POM in high-humidity conditions exhibit a shorter fatigue life than in low- and medium-humidity conditions, and (2) the fatigue strength of polymer is considered to be influenced by the elastic properties of the specimen surface. With the measurement of leaky surface skimming compressional wave (LSSCW) velocity, elastic properties in microareas of the polymer became clear.