Real-time displacement monitoring of a composite stiffened panel subjected to mechanical and thermal loads

Real-time reconstruction of the deformed structural shape using in situ strain measurements is an inverse problem, commonly called shape sensing. The knowledge of the deformed structural shape in real time has important implications for assessing strain, stress, and failure states, and thus constitutes a key component of structural health monitoring. In addition, shape sensing is required for control and actuation of smart structures. In this paper, shape sensing analyses are carried out for typical composite stiffened structures using the inverse Finite Element Method (iFEM). By using a limited set of discrete strain data, iFEM allows full-field reconstruction of displacements that can thus be monitored also far from sensor locations. First, the iFEM theoretical framework and the formulation of a triangular, inverse shell element are briefly discussed. Then, a general strain-sensor configuration amenable to stiffened shell structures is proposed. Several numerical results are presented for static, dynamic, and thermal loadings. The robustness of the method with respect to input errors is also investigated. It is shown that iFEM is a viable methodology for shape sensing of composite stiffened structures, having the desired computational efficiency, accuracy, and robustness with respect to strain-measurement errors. The iFEM shape-sensing methodology is particularly attractive because it does not require any information regarding applied loading, elastic material constants, inertial properties, or damping characteristics.