Lock-in thermography as a tool for fatigue damage monitoring of composite structures

Abstract

Fatigue dimensioning of composite structures has become a great challenge in the aeronautic industry. The estimation of the fatigue limit requires time-consuming experimental campaigns: millions of mechanical cycles are applied to one studied sample until failure, for several load levels. The alternative discussed in the present paper is to monitor the self-heating of carbon/epoxy composites under a significantly reduced number of load cycles, in order to define fatigue damage indicators. The chosen approach is to use lock-in thermography, which makes it possible to analyse the first harmonics of the heating signal, not matter how noisy it might be.

Thermography-based approaches for multi-scale damage assessment in woven composite materials

“…The present study aims at assessing the sensitivity of various thermography-based approaches to multi-scale damage in woven composites. Three experimental techniques are considered: standard pulse thermography, used to inspect the material after the mechanical tests (Section 2); passive thermography, used to monitor the damage under mechanical loading (Section 2); lock-in thermography, used to visualize the harmonics of the thermal signal that might contain decisive data regarding the composite damage [5] (Section 3). In each case, advanced data processing methods are applied to improve the signal-to-noise ratio (SNR).…”