The goal of this paper is to investigate the ability of the heat build-up technique to predict the fatigue lifetime of injected thermoplastic reinforced with short carbon fibers. Several commercial grades and filler ratios are considered here in order to challenge the ability of the technique to capture the influence of these variations. First, the materials are investigated and the mechanical and thermal protocols are described. The way to build the heat-build-up curves is outlined. Then the results obtained from the heat build-up and fatigue experiments are presented. The heat build-up curves are obtained both from measurements performed on the front surface of the sample and from the side surface. Finally, these results are used to discuss two main points. The first is the validity of the hypotheses needed to apply the approach, ranging from the evaluation of the dissipation to the fatigue response. The second is the capability to predict the fatigue curves accurately throughout an energetic criterion, and to identify the influence of the variations of matrix grade and fiber content on the fatigue properties. It appears that the predictions obtained match the results obtained from classic fatigue tests and validates the use of the technique for fast material screening.

A constitutive model for the cyclic behaviour of short carbon fibre-reinforced thermoplastics for aeronautical applications is proposed. First, an extended experimental database is generated in order to highlight the specificities of the studied material. This database is composed of complex tests and is used to design a relevant constitutive model able to capture the cyclic behaviour of the material. A general 3D formulation of the model is then proposed, and an identification strategy is defined to identify its parameters. Finally, a validation of the identification is performed by challenging the prediction of the model to the tests that were not used for the identification. An excellent agreement between the numerical results and the experimental data is observed revealing the capabilities of the model. Keywords Short fibre-reinforced thermoplastic • Cyclic loading • Constitutive equations • Complex experimental database • Thermodynamics of irreversible processes Communicated by Johlitz, Laiarinandrasana and Marco.