Browsing by Author "Freitas, M.J.M."
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- Combined numerical-experimental model for the identification of mechanical properties of laminated structuresPublication . Araújo, A.L.; Soares, C.M. Mota; Freitas, M.J.M.; Pedersen, P.; Herskovits, J.A combined numerical-experimental method for the identification of six elastic material modulus of generally thick composite plates is proposed in this paper. This technique can be used in composite plates made of different materials and with general stacking sequences. It makes use of experimental plate response data, corresponding numerical predictions and optimisation techniques. The plate response is a set of natural frequencies of flexural vibration. The numerical model is based on the finite element method using a higher-order displacement field. The model is applied to the identification of the elastic modulus of the plate specimen through optimisation techniques, using analytical sensitivities. The validity, efficiency and potentiality of the proposed technique is discussed through test cases.
- Damage localization in laminated composite plates using double pulse-electronic holographic interferometryPublication . Santos, J.V. Araújo; Lopes, Hernani; Vaz, M.A.P.; Soares, C.M. Mota; Freitas, M.J.M.One method for the damage localization of impact damage in laminated composite plates, based on their vibrational characteristics, is presented in this paper. This method uses double pulse-electronic holographic interferometry for mode shapes acquisition and the differences in curvatures. The rotations and curvatures are numerically obtained. The method is applied to a carbon fibre reinforced epoxy rectangular plate, free in space, subjected to two cases of impact damage. It is shown that the method based on curvatures allows for the localization of both cases of damage, which can be undetected by visual, X-ray or C-Scan inspections. The best localizations are achieved by selecting and applying the method to the most changed mode.
- Damage localization in laminated composite plates using mode shapes measured by pulsed TV holographyPublication . Santos, J.V. Araújo; Lopes, Hernani; Vaz, M.A.P.; Soares, C.M. Mota; Freitas, M.J.M.Three methods for the damage localization of impact damage in laminated composite plates, based on their vibrational characteristics, are presented in this paper. These methods use double pulse TV holography with acoustic excitation for mode shapes acquisition and the differences in translations, rotations and curvatures. The rotations and curvatures are obtained by numerical differentiation of mode shapes translations using a differentiation/smoothing technique. The methods are applied to a carbon fiber reinforced epoxy rectangular plate, free in space, subjected to two cases of impact damage. It is shown that the method based on curvatures allows the localization of both cases of damage, which can be undetected by visual, X-ray or C-scan inspections. The best localizations are achieved by selecting and applying the method to the most changed mode.