Delamination localisation and length estimation in composite laminate beam by VSHM and pattern recognition methods

The focus of this work is to investigate the delamination damage in laminate composite beams, to fix a Vibration-based structural health monitoring (VSHM) method for the laminate structures. The analysis is concentrated on the vibration characteristics of the samples and, in particular, the attention is addressed on the first several natural frequencies of a composite laminate beam with a delamination damage. The core of this work is an experimental investigation on the vibration response of a composite laminate beam and its changes caused by delaminations with different sizes and in different locations of the beam. The study is divided in 3 sections: delamination detection, delamination localization, and delamination estimate. The aim is to determine how the first six harmonics frequencies change due to the delamination, and the results show that they can be successfully used to investigate the presence, the location and the dimensions of the delamination in a composite beam. A Pattern Recognition analysis is used to locate the damage, while the detection and the evaluation are done using the changes in the harmonic frequencies. A finite element analysis is performed, and the variations of the natural frequencies due to delamination are in good agreement with the experimental results.