EFFECT OF TEMPERATURE ON FATIGUE-CRACK GROWTH IN UNPLASTICIZED POLYVINYL-CHLORIDE

The effect of temperature on the fatigue crack growth in a 1 50 mm class 1 2 unplasticized polyvinyl chloride (uPVC) pipe-grade material over a temperature range -30 - 60-degrees-C was studied. The Arrhenius relationship between fatigue crack growth rate, da/dN, and absolute temperature, T, was found to describe the experimental data very well independent of the applied stress intensity factor range, DELTAK In the temperature range -30 - 10-degrees-C the activation energy was 8.8 kJ mol - 1 and between 26 and 60-degrees-C this was 30 kJ mol - 1. The two activation energies were found to be associated with two distinctly different crack growth mechanisms. In the low-temperature range there was a predominant shear mechanism, but in the high-temperature range multiple crazing was the major fatigue mechanism. Finally, a ''stress intensity factor''-biased Arrhenius equation for fatigue crack growth was suggested and found to predict rather accurately the data of uPVC, as well as those of other polymeric materials at different temperatures.