Experimental and numerical study of creep and creep rupture behavior of PA6

Polyamide 6 (PA6) is a semi-crystalline polymer utilized in many structural components working under steady load. At room temperature, PA6 exhibits time dependent (viscoplastic) deformation. The aim of this work is to investigate the mechanical response and the crack growth of PA6 under creep conditions.The experimental database consists of tests carried out on smooth and notched round bars. Load versus displacement curves were recorded for monotonic tests tensile at various crosshead speeds. Then, creep tests at constant load were performed allowing the record of the creep strain history according to the applied load.Microscopic observations highlight the initial spherulitic structure.Smooth and notched specimens were utilized in order to identify and to validate material coefficients dedicated for analytical modeling. The non linear fracture mechanics for creeping solids was applied to results on “pre-cracked” specimens. For this kind of loading, use of the load parameter C∗ is recommended.By plotting C∗ values versus time to failure, a unique correlation was obtained. The knowledge of this master curve allows lifetime assessment of PA6 cracked bodies.