GW imaging enabled adaptive quantitative monitoring of impact damage

Due to the poor resistance to impact, composite aircraft structures are prone to impact damage during service, which may significantly reduce the load-bearing capability and flight safety. The guided wave (GW) based structural health monitoring (SHM) method has proved to be effective and promising in diagnosing impact damage of composite structures, therefore has been widely researched. When considering GW based quantitative monitoring of impact damage, there exists a major concern that the dispersion caused by complex structural form and damage development will severely affect the monitoring accuracy of damage size. Aiming at accurate size estimation of impact damage for complex composite aircraft structures, this paper proposes for the first time an imaging improved adaptive quantitative monitoring method. In this method, a multi-domain feature fusion enhanced quantitative diagnostic model is first established for every sub-region of structure divided by the adopted piezoelectric transducer (PZT) network. Then the PZT network-based GW imaging is performed to locate the sub-region that impact damage occurs, and enable the adaptive selection of the corresponding quantitative diagnostic model, by which the dispersion can be effectively avoided and the damage size can be accurately estimated. Experimental research is conducted on stiffened carbon fiber panel structures of aircraft to analyze real impact damage caused influence on GW signal and verify the proposed method. Through generating impact damages with different positions and sizes on one stiffened structure by impact hammer, quantitative monitoring models corresponding to different sub-regions are established and used to estimate damage size on another stiffened structure. The average error of size estimation of impact damages at different sub-regions is only 1.7 mm, which demonstrates the effectiveness of the proposed method and its potential in quantitative damage monitoring of large-scale composite aircraft structures.