Effect of bending modes on failure analysis of adhesively bonded composite structures

This research paper addresses the critical issue of identifying structural health conditions of bonded composites when subjected to varying bending modes. In response to heightened demands for eco-efficiency, the aviation sector has embraced lightweight designs, with composite materials supplanting traditional aluminum due to their remarkable tensile stiffness and reduced weight. However, the practical utilization of bonded composites introduces challenges, as non-uniform loads can lead to bending and deformation, potentially hindering failures detection capabilities within the bonded structures. This study explores the technology details for employing guided waves to assess health conditions. The damage extent is analyzed by capturing the reflected guided waves that propagate in the bending deflection of the bonded composite strip. The analytical results are also resolved aiming to compare with experiment and simulation results, which explains in more detail the propagation process of guided waves in bent materials. The Scanning Laser Doppler Vibrometry (SLDV) techniques are used to visualize the full wave fields. The research results show that the bending of the composite structure exerts a discernible impact on the guided wave's ability to accurately quantify cracks. Consequently, the indicators used to gauge faults undergo notable shifts in correspondence with these variations. Notably, employing a prognosis model trained via a sample with zero deflection, to predict the Remaining Useful Life (RUL) of a deflected sample introduces uncertainty error. This underscores the intricate relationship between deflection-induced changes and damage prediction using guided wave analysis. The deviations that occur in the process of predicting RUL serve as a pivotal reminder of the intricate nature of damage assessment in the presence of deflection, warranting comprehensive consideration in the development of predictive models based on bent specimens.