Shape and Stress Sensing of Thin Stiffened Composite Panels Using iFEM Methodology

Thin stiffened composite panels (TSCPs) are often used in the aerospace industry due to their low weight and high load-bearing capacity. However, harsh environmental conditions can lead to delamination and structural failure. Structural health monitoring (SHM) systems, especially for shape sensing, help to detect such failures in real time. The inverse finite element method (iFEM) is a robust shape sensing technique that minimizes a weighted least-squares function to match experimental strain measurements with theoretical predictions. In this study, the iFEM-iQS4 inverse shell element is applied to a TSCP to enable accurate shape and stress reconstruction from sparse sensor data. For this purpose, a rectangular stiffened multilayer laminate with symmetric cross-ply made of carbon fiber epoxy material is considered. Two models of sensor placement, "Full" and "Reduced", are evaluated. The "Full" model includes all elements with strain sensors, while the "Reduced" model uses only circumferential elements. The accuracy of the shape and stress sensing is evaluated by comparing the iFEM results with the FEM results. It is shown that iFEM-iQS4 effectively predicts deformation and stress fields despite the use of a limited number of sensors, demonstrating its potential for efficient SHM of TSCPs in real time.