Evaluation of damage in composites by using thermoelastic stress analysis: A promising technique to assess the stiffness degradation

The stiffness degradation represents one of the most interesting damage phenomena used for describing the fatigue behaviour of composites. A critical aspect of modelling the damage is represented by the simulation of the whole behaviour of the composite and by the assessment of the actual stiffness for the models validation. In this work, the stiffness degradation of quasi-isotropic carbon fibre reinforced polymer (CFRP) obtained by automated fibre placement has been assessed by means of thermoelastic stress analysis. The amplitude of temperature signal at the mechanical frequency (thermoelastic signal) was considered as an indicator of material degradation and compared with the data provided by an extensometer. The correlation between thermoelastic and mechanical data allowed to build a new experimental model for evaluating and predicting material stiffness degradation by just using thermoelastic data. The proposed approach seems to be very promising for stiffness degradation assessment of real and complex mechanical components subjected to actual loading conditions.