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.