Modeling and identification of a new fatigue damage model for injection-molded short glass fibre reinforced thermoplastics

Modélisation et identification de lois de comportement avec endommagement en fatigue polycyclique de matériaux composite a matrice thermoplastique

Hedi Nouri (1)

1 LPMM - Laboratoire de physique et mécanique des matériaux

The present work is a contribution to the phenomenological modelling of fatigue non-linear cumulative diffuse damage in short glass fibre reinforced thermoplastic matrix composites. In such materials, fatigue damage kinetic exhibits three stages, namely: i) material softening and damage initiation, ii) coalescence and propagation of micro-cracks, iii) macroscopic cracks propagation and material failure. The proposed model is built in the framework of the continuum damage mechanics and aims at predicting these three stages of the damage evolution. It extends the previous approach and takes into account the important stiffness reduction observed during the first damage stage. The above is modelled by the integration of a combined Norton-like power law and an exponential law expressing the damage rates as a function of the associated thermodynamic dual forces. The model has been formulated in terms of strain energy, so that makes easy its numerical implementation into the finite element code Abaqus/Standard through a user defined material subroutine UMAT. Damage evolutions predicted by the developed model reproduce well those observed for this kind of composites under cyclic loading. Two identification strategies are developed. The first identification strategy based on homogeneous tensile fatigue tests performed in the longitudinal and transversal directions of a PA6-GF30 and a PP-GFL40. A second identification strategy based on the use of optical whole-field displacement/strain measurements by digital image correlation coupled to an inverse method from one single coupon.

Les matériaux composites thermoplastiques constituent une solution technologique de premier ordre pour la fabrication de pièces et de composants fonctionnels ou de structure notamment pour l'industrie automobile. Le travail abordé dans le cadre de cette thèse constitue une contribution à la compréhension et à la modélisation de la cinétique d'endommagement dans les thermoplastiques renforcés par des fibres de verre courtes (PA6

Mots clés: Fatigue; Short glass fibre reinforced thermoplastic; Damage; Composite; Thermoplastic; Glass fibre; Damage model

Mots clés: Endommagement des composites; Thermoplastiques renforcés; Fibres de verre; Modélisation de l'endommagement

Domaines: Sciences de l'ingénieur [physics]

Hedi Nouri. Modélisation et identification de lois de comportement avec endommagement en fatigue polycyclique de matériaux composite a matrice thermoplastique. Sciences de l'ingénieur [physics]. Arts et Métiers ParisTech, 2009. Français. ⟨NNT : 2009ENAM0015⟩. ⟨pastel-00005669⟩