Full-field monitoring methods for damage analysis on aeronautical CFRP specimens under fatigue loads

Abstract

Abstract The present paper is focused on full-field experimental monitoring procedures to be employed during HCF fatigue testing on two series of CFRP open hole samples. Two different experimental methodologies based on thermographic techniques and displacement measurements with Digital Image Correlation (DIC) analysis are employed for damage settlement and evolution to be detected up to failure, together with correspondent compliance analysis. Combined monitoring approaches, based on thermo-elastic and dissipative phenomena, together with stiffness properties variations, are claimed to offer precise damage state localization during tests in real time; in addition, DIC analysis is performed during low-frequency fatigue cycle is studied for better failure prediction and damage location. The thermal parameters and experimental compliance correlation seem to indicate similar signal variation during damage progress and after proper data elaboration; contemporaneous raw thermal measurements in critical zones of specimens under fatigue life offer a kind of delamination recognition at specific layer interface and location, as well as propagation before final failure. Sample under tensile load on the other hand reveal delaminations indirectly on the surface. In addition, non-destructive thermographic and ultrasound tests are performed at regular intervals during fatigue life.