Comparison of strain pre-extrapolation techniques for shape and strain sensing by iFEM of a composite plate subjected to compression buckling

The inverse Finite Element Method (iFEM) is a model-based technique for structural shape sensing based on a pattern of input strain data experimentally acquired on the structure. It is independent of the external load and material properties, making it a valid approach for composite materials monitoring. In this framework, the iFEM shape sensing capability is experimentally investigated on a carbon fiber reinforced polymer plate subjected to a compressive buckling condition. As logistic constraints impede strain sensor installation in all the desired locations, Smoothing Element Analysis (SEA) and polynomial fittings are used to pre-extrapolate the whole plate's strain field. Finally, after a sensitivity analysis on the input strain pre-extrapolation, the iFEM displacement reconstruction is validated with three lasers' independent measurements and direct FEM results, investigating the local and global shape sensing capability.