Effective Optical Fiber Sensing Method for Stiffened Aircraft Structure in Nonlocal Displacement Framework

As a common object of the fuselage and wing, the stiffened structure has been widely used in aerospace and other fields. Due to the geometry complexity of the stiffened structure, such as variable cross section and changing bending stiffness, the existing reconstruction methods are difficult to accurately reconstruct the structure shape. Therefore, a novel measurement algorithm is designed by coupling Erigen's differential nonlocal theory and inverse finite element method (iFEM) for real-time shape and strain monitoring of the stiffened structures. The hybrid method, based on fiber Bragg grating (FBG) strain measurement, can meet the needs of lightweight and real-time deformation monitoring. Initially, the distribution theory and sign function are employed to describe the generalized constitutive formulations of stiffened structures. Subsequently, the initial curvature was proposed for the first time to solve the strain discontinuity based on the macroscopic effects of Erigen's differential nonlocal formulation. Next, the classic iFEM was employed to reconstruct structural displacements using measured surface strain. Then, the finite element (FE) model of the stiffened structure is established to verify the accuracy and applicability of the present method in the numerical calculation. Finally, the shape sensing methodology is experimentally validated in an actual wing-integrated antenna structure under different loading cases. Overall, the presented hybrid algorithm fills the gap in the reconstruction of stiffened structures with a small number of sensors and expands the engineering application of iFEM.