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Components made of short glass fiber reinforced thermoplastics are increasingly used in the automotive industry in order to reduce the price and weight of the vehicule. These components are frequently submitted to fatigue loadings during their service conditions. Therefore, a good conception towards the fatigue phenomenon is mandatory. One preliminary need is to model correctly the non linear behavior of such material, which is clearly not an easy task due to the numerous dissipation mechanisms involved and the strong anisotropy induced by the injection process. In this study, we present some results on injected samples with a specific geometrical accident leading to a stress concentration factor Kt=2.5. A specific thermomechanical characterization is done using an infrared camera. Several key informations can be extracted from these experimental data: temperature variations, heat sources, crack initiation localization, crack propagation (detection of the crack vicinity), etc.These data are then compared to numerical simulations involving the simulation of the injection step and finite element analysis using an anisotropic elasto-viscoplastic model. The heat sources obtained with the model are compared the experimental ones. A very good agreement between the experimental data and the numerical ones is found which illustrate the relevancy of the model to capture some key thermomechanical properties of these materials, which is obviously a key element in the fatigue life prediction.