Shape Sensing with Inverse Finite Element Method on a Composite Plate Under Compression Buckling

The inverse Finite Element Method (iFEM) is an algorithm able to compute the deformed shape of a structure starting from its geometry, the boundary conditions, and the strain data measured on discrete positions of the structure, without prior knowledge on material properties and load condition. A critical point of this technique is the sensor pattern optimization for a correct strain field reconstruction. Sensors cannot be applied on the whole structure due to the presence of the physical boundary conditions and logistic constraints, potentially leading to a wrong reconstruction of the deformed shape by the iFEM. Thus, the Smoothing Element Analysis (SEA) is used in this work for prior extrapolation of the strain field in locations where sensors are not available. A sensitivity analysis highlights the influence of the mesh size and different SEA hyper-parameters over the extrapolated strains, which are then provided as input to the iFEM for shape sensing. The method has been verified with experimental tests on a CFRP specimen sensorised with fiber optic, subjected to a compressive load, proving the iFEM can compute the deformed shape of the structure also in presence of a buckling condition. The iFEM results are validated with experimental displacement measures from lasers.