Test equipment for fatigue crack growth testing of polymeric materials in chlorinated water at different temperatures

Abstract

In this research, a test arrangement was designed and implemented that allows for fatigue crack growth testing in chlorinated water utilizing a conventional electro-dynamic testing machine. The developed equipment enables the quasi-automatic, in-situ determination of fatigue crack growth rates under non-interrupted loading via an optical crack length measurement device. The test system consists of three main units, a chlorine control unit, a temperature control unit and an environmental containment for the test specimen. The chlorine content may be held constant at specific pH values in the range from 0.1 to 10 ppm, and the temperature may be controlled in range from 23 °C to 95 °C. In terms of specimen configuration, tests can be performed with cracked round bar and compact type specimens. In order to demonstrate the performance of this test system, two polymer grades (polypropylene and 30 w% short-glass fiber reinforced polyamide) were tested. Both materials exhibited a decreasing fatigue crack growth resistance with increasing chlorine content and with increasing temperature.