Effect of notch root radius on the creep failure mechanisms on polyamide 6 : application of facture mechanics approaches

Abstract : The polyamide 6 (PA6) under study exhibits non-linear time dependent (viscoplastic)deformation when submitted to steady load (creep) at room temperature. An experimentaldatabase consisting of creep tests performed on notched round bars with various notch rootradii was built. Failure mechanisms of the PA6 material were investigated thanks tocomprehensive microscopic examinations of deformed and broken specimens. Globalapproach of fracture mechanics for creeping solids was applied and showed its limits.Alternatively, the local approach of fracture mechanics was attempted, with the help of finiteelement analysis. It was shown that this approach could successfully capture main featuresof creep damage mechanisms of the PA6 material, which lead to complete failure.