Parameters identification of fatigue damage model for short glass fiber reinforced polyamide (PA6-GF30) using digital image correlation

The work deals with the parameters identification and the experimental validation of a phenomenological model for fatigue anisotropic damage in short glass fiber reinforced polyamide (PA6-GF30). The damage fatigue model has been formulated in terms of strain energy and was implemented into the finite element code ABAQUS/Standard through a user defined material subroutine UMAT. The present paper focuses mainly on the identification strategy based on homogeneous and heterogeneous fatigue tests. Damage parameters governing longitudinal and transversal damage (d(LL) and d(TT)) are identified from homogeneous tension-tension fatigue tests performed in both material directions. The damage parameters governing the shear induced damage (d(LT)) are identified using heterogeneous fatigue tests carried out on a specific configuration. This heterogeneous fatigue test gives rise to non-uniform distributions of the in-plane strain components: epsilon(LL), epsilon(TT) and epsilon(LT). Heterogeneous strain fields are measured by the digital image correlation technique (DIC) during the fatigue test. The in-plane strain components are coupled to numerical computations through an inverse method to determine the parameters set governing the shear induced damage. The comparison between the damage model predictions and the damage curves obtained from fatigue tests shows a good agreement in both material directions. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of ICM11