The problem of detection of localised porosity through the thickness in composite materials has been considered following a coupled experimental and modelling approach. Samples with porous plies among otherwise safe materials have been manufactured using a precuring technique. A Finite-Difference model allowing the propagation of waves in a medium extracted from photomicrographs has been used for simulations concurrently to ultrasonic measurements on the manufactured samples. The simulation and experimental results turned out to agree on the main characteristics of the recorded signals, which gives confidence into the model. The characteristics of the presence of localised porosity have been found to be discontinuities of the frequency spectrum of the structural signal, and ruptures of the regular and monotonic decrease of the structural signal. The signature of localised porosity depends on the local rate of porosity. High rates yield echoes and an energy bump, low rates yield an energy decrease when averaging over different transducer positions. As for the frequency content, porosity in the bulk of the part yields a frequency disturbance, and porosity at the front of the material forbids the reaching of the resonant frequency after the front echo.
Ultrasonic non-destructive inspection of localised porosity in composite materials
Zerstörungsfreie Ultraschallprüfung lokaler Porositäten in Verbundwerkstoffen
2006
8 Seiten, 7 Bilder, 1 Tabelle, 5 Quellen
Conference paper
Storage medium
English
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