Theoretical and experimental study on carbon/epoxy facings-aluminum honeycomb sandwich structure using lock-in thermography

Carbon/epoxy facings-aluminum honeycomb sandwich structure (C/E FAHS) is widely used in aircraft and aerospace with the merit of high-specific strength, high-specific modulus and lightweight. However, layered debonding as the main defect type of C/E FAHS affects the material performance seriously. Therefore, in this present study, lock-in thermography was introduced to detect debonding defects of C/E FAHS. A three-dimensional finite element model (FEM) of this material stimulated by sinusoidal excitation signal was built. The influence of modulation parameters (i.e. modulation frequency, light power intensity, and the number of excitation cycles) and the structural parameters of carbon/epoxy facings were analyzed. Furthermore, C/E FAHS specimens were detected by lock-in thermography. The experimental study on the influence of modulation parameters and structural parameter was carried out. Results demonstrated that lock-in thermography was an effective method to detect debonding defects of C/E FAHS.