Damage localisation in pultruded materials based on experimental model analysis

The object of the work is a simply supported beam made of pultruded material, i.e. resin and fibre of glass, on which dynamic tests are carried out by exciting the structure with a hammer and recording the displacements by means of sensors. After the distances between the accelerometers and the impact positions of the hammer have been determined, the test is carried out. Once all the information has been acquired, data processing is performed, obtaining frequencies and modal shapes for the first four modes of vibrating. Modal shapes are in turn analysed using the Treed Gaussian Process (TGP) to identify and locate the crack.The TGP is a statistical method based on the regression of Gaussian processes. Gaussian Processes (GP) are the extension from the distribution of scalar values to functions; in other words, through Gaussian Processes a function is obtained in which every point represents a probability function. The TGPs use Gaussian Processes, but interpolation is not done on the whole domain; the latter is divided into two parts, obtaining two interpolating functions. At the next step each individual part of the domain could be divided into two other parts and so on. The points that divide the domain are points in which there is a local variation of the function. In this case, will be due to the presence of a crack.Parallel to the experimental data, four models of cracked beams are created by means of FEM on which dynamic parameters and modal shapes are determined. This is done as a support, to compare the results with the experimental ones. The FEM models differ according to the size of the crack: 1, 10, 25 and 50 millimetres. The position of the crack is inserted at the position of 3.65 m from the origin of the beam; this choice is completely arbitrary. Once the modal analysis is performed, the first four modal shapes are analyzed through Treed Gaussian Process. To locate the crack, on FEM models, the "curvature method" is also applied: it identifies the position of the crack making a difference between the curvatures of the cracked and intact model.The objective of the work is to understand whether a TGP analysis can detect a possible crack position on the real beam.