Florian Arbeiter, Martin Ševčík, Gerald Pinter, Frank Andreas, Pavel Hutař
Papers # 2014 Chicago
Multi-layer pipes made from polypropylene have been widely used in sewerage applications for several years. Due to good material properties and generally low mechanical loads not many critical failures occur. Aim of this work is to determine, whether slow crack growth, consisting of crack initiation and crack growth, could be a threat to the integrity of pipes made from polypropylene. In contrast to pressurized vessels, where SCG is a known and well-studied problem, there is, to the authors’ knowledge, not much work in the area of slow crack growth in non-pressure polypropylene pipes. Work previously presented at the PPXVI showed, that the use of fracture mechanic methods, especially with cyclic loading, can be used to induce quasi-brittle failure in mineral reinforced polypropylene block copolymers. This paper presents results on the cyclic fatigue tests of un-reinforced polypropylene block copolymer, and crack growth kinetics for the reinforced middle layer for different loading ratios. By using these results it was possible to show, that the phenomenon of slow crack growth can occur in both, reinforced and un-reinforced polypropylene block copolymer. However, under the precondition of loading within standardized ranges, it seems not to be a decisive mode of failure within the demanded lifetime of said pipes.