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International audience; To reinforce the environmental standards, we need to strengthen the lightening of vehicles and to generalize new composite materials in order to reduce weight. To use these innovative composite materials in the mass production of automotive parts, it is essential to propose a predictive approach of the S-N curves, which must be established for each new composite formulation and for several types of microstructure within real components. Although these preliminary characterizations consume time and money, this paper proposes two hybrid methodologies to predict the fatigue life during the fatigue test. Both methodologies are based on micromechanical modeling which is developed under monotonous loading with fatigue effects under different amplitudes. The suggested methodology is based on an experimental analysis of monotonic behavior under fatigue loading and on multi-scale modeling of damage. In the results, the proposed model and the used approaches are in good agreement with the experimental results.

The aim of this paper is to develop a probabilistic approach of high cycle fatigue (HCF) prediction of glass fiber-reinforced epoxy composites by taking into account the modifications induced by the variation of the loading parameters (stress and number of cycles) and those of the material parameters (fiber Young’s modulus and fiber volume fraction). Using fatigue curve analytical expression and Monte Carlo simulation assessment, probabilistic Wohler curves are plotted to predict the high cycle fatigue behavior of the material. In this regard, four cases are studied by varying the hypothesis for the stress and number of cycle values to be probabilistic or deterministic. The design of experiment (DoE) techniques are used in this work by varying the factors of interest in a full factorial design to evaluate the effect and the interaction of some factors influencing the fatigue reliability. The controlled input factors of the process are traduced by (i) the materials’ parameters represented by the variation of fiber and matrix Young’s moduli (E f and E m ) and the fiber volume fraction (V f ) and either traduced by (ii) the loading parameters represented by the applied stress and number of cycles.

International audience; The majority of fatigue life prediction models which have been proposed for the Short Fiber Reinforced Composite (SFRC) materials have been developed for constant temperature. However, in real situations, SFRC structures are subjected to variable temperature. This study focus on the response of SFRC composites subjected to different sequences (or blocks) under variable temperature conditions. Experientially, this kind of study requires a lot of investment from the point of view of cost and time. In this paper, the results coming from modelling the fatigue life and residual stiffness of short fiber reinforced composites subjected to thermomechanical loadings are reported. In fact, we propose to use a hybrid micromechanical-phenomenological model to quantify the evolution of the local damage rate during each loading block. Indeed, damage accumulation is calculated and cumulated step by step through the calculation of the evolution of a local damage ratio which describes the evolution of micro-cracks density until failure. Life prediction for specimens submitted to a variable temperature loading found to give acceptable results compared to experiments.