Applicability of Strain Controlled Cyclic Tests for Short Fibre Reinforced Polymers

Abstract

To develop parts, made of short glas fibre reinforced (sgfr) polymers for industrial purposes, a comprehensive material knowledge is necessary. Especially the material behaviour under cyclic loads has a great influence on the life time of parts. Parts are often used under complex load cases (stress state, temperature, ...), therefore it is indispensable to understand the effect of the main influence factors. High loads within load histories as well as stress concentrations can lead to plastic deformations. To cover this in an early stage of the development process, a closed simulation chain should be established. Therefore, the applicability of common material models (e.g. fatigue criteria according to Ramberg-Osgood) has to be studied first, the models have to be adapted or even new models have to be found for sgfr materials. This work focuses on the applicability of strain controlled cyclic tests for glass fibre reinforced polymers. Hereby the cyclic stress rearrangement in the low cycle regime of the S/N-curve can be described. Therefore, tests were performed on a 50 wt% sgfr partial aromatic polyamide. For the fatigue tests un-notched, injection moulded specimen were used. The tests show a principal applicability of strain controlled LCF-tests for sgfr polymers.