A new model for fatigue life prediction based on infrared thermography and degradation process for CFRP composite laminates

In this paper, a new fatigue life prediction methodology is proposed by combining stiffness degradation and temperature variation measured by InfraRed Thermographic (IRT) camera. Firstly, the improved thermographic method is used to determine the fatigue limit by using the data of stabilized temperature rising. Following this, a two-parameter model is proposed to characterize the stiffness degradation of CFRP laminates with the increase of cycle numbers. After the calibration parameters and the calculation of the normalized failure threshold stiffness, the whole S - N curve can be obtained in a very short time. The proposed model is applied to both the experimental data of triaxially braided CFRP laminates from literature and those of unidirectional CFRP laminates obtained from our fatigue tests. Results show that predicted S - N curves have a good agreement with traditional tests. The principal interests of this model could be listed as follows; (i) it is a more general criterion applicable to different materials; (ii) it has more physical senses; (iii) it allows the determination of the total S-N curve for composite materials in a short time.