An experimental study on damage intensity in composite plates subjected to low-velocity impacts

Today composite structures are widely used in different industries. Since these structures are sometimes experienced impacts of low-velocity objects, evaluating the intensity of the damage due to the impact in these structures seems important and necessary. In this article, the effectiveness of the thermography method with three different thermal excitation sources, including the ultrasonic vibrothermography, infrared thermography with the heating element, and infrared thermography with hot airflow, for damage evaluation in CFRP and GFRP composite plates subjected to low-velocity impacts are investigated. The ultrasonic vibrothermography method is introduced as the most promising technique for damage evaluation in CFRP and GFRP composite plates subjected to low-velocity impacts, and the effect of the excitation power and excitation frequency on the effectiveness of this method is studied. To find the damage location in the thermography images in which the damage is not clear enough to be identified, the wavelet transform is applied while it is not suitable for calculating the damaged area. Finally, finite element (FE) simulations are carried out for the case of an internal defect. The results show the acceptable accuracy of the FE simulation in comparison with the experimental results.