Resumo:
Laminated composite structures suffers from delamination, the detachment of the layers due
to the rupture of the fiber-matrix interface, as their principal mode of failure. Differently
from other damages, such as cracks, delaminations are often not visible on the surface
causing a late detection and leading to sudden failures. To ensure that laminated composite
structures operate flawlessly, precise monitoring methods are required. The present study
proposes a damage index to identify delaminations in a laminated composite beam, yet,
the development is based on a well-defined methodology. The proposed damage index is
composed of a weighted sum of Discrete Wavelet Transform detail coefficients, obtained
by applying the transform to the mode shapes of the structure. Numerical models of the
beams with a stiffness reduction in limited areas to simulate damage, provided data for
tuning the coefficients of the damage index by performing a mixture design analysis and a
multiobjective optimization. After substantial results for identifying damage in numerical
cases, the damage index efficiency was tested with real carbon fiber-reinforced polymer
beams. The experimental specimens were manufactured with delaminations induced by
embedding non-sticking films between the layers. Again, substantial results in identifying
damaged were achieved. The damage index proved to be efficient to locate damage in
almost all positions along the beam. It is important to emphasize that the proposed
damage index is a no-baseline method, a method that does not require information of the
pristine structure. Finally, this study performs a deep statistical analysis on the effects of
damage characteristics, such as position and severity, in a damage identifying technique.
The results of the analysis serves as basis for developing more sophisticated and optimized
damage identifying methods.
