Damage Identification by Inverse Finite Element Method on Composite Structures Subject to Impact Damage

One main limitation to the implementation of an SHM system on real structures is the difficulty to accurately define the load boundary conditions and the material properties, possibly leading to damage misclassification, especially with heterogeneous materials like composites. In this framework, the inverse Finite Element Method (iFEM) enables to reconstruct the complete displacement, and thus, the strain field starting from discrete strain measures without any a priori knowledge of the loading condition and the material properties. Structural assessment is then performed by computing an anomaly index identifying discrepancies between the strain reconstructed and measured in some testing positions and exploiting the latter for computing the Mahalanobis distance to further highlight discrepancies. Though the anomaly identification framework is general for any arbitrary component geometry and damage type, the procedure is experimentally verified with a CFRP reinforced panel subjected to a compressive load with propagating delamination generated from bullet damage.