Inspeção de materiais compósitos utilizando ondas acústicas guiadas

• Ano de defesa: 2015
• Autor(a) principal: Granja, Silvio Cesar Garcia [UNESP]
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual Paulista (Unesp)
• Palavras-chave em Português: Anisotropia; Matéria - Propriedades; Ultrassom; Processamento de imagens; Image processing
• Link de acesso: http://hdl.handle.net/11449/126546; http://www.athena.biblioteca.unesp.br/exlibris/bd/cathedra/13-08-2015/000844171.pdf

In this thesis, a detailed study of ultrasonic non-destructive evaluation in plain woven fabric composite plates is performed. A review of analytical and experimental methods for the de- termination of the characteristic equations of the propagation modes and methods for obtain- ing numerical solutions of the elastic constants of the composite and dispersion curves of anisotropic material plates were performed. Some descriptions of textile composites are pre- sented, specifically the 2D orthogonal plain woven fabric carbon-fiber epoxy. Phase and group velocity dispersion curves, skew angle and focusing factor were obtained by numerical simula- tion for the symmetric and antisimetric modes of wave propagation using a multi-layer model with [0/90/45/90/0/90/-45/90/0]. Each layer is made of carbon fibers in the 2D orthogonal plain weave fabric format (T300) in an epoxy matrix (F155). The transfer matrix method was used to model the multilayer composite, resulting in the determination of the propagation modes from their phase/group velocities as a function of frequency and propagation direction in the lami- nate. Experimental approaches were made to validate the theoretical predictions. Two broad- band transducers coupled to acrylic wedges were used with different angles for speed selection, operating in transmission-reception system; scans of the plates with two types of laser vibrom- eters were also used to measure wave propagation. The results were analyzed by comparing the phase velocities, the wave curves and elastic focusing patterns of the A0 and S0 modes, showing agreement with the prediction of the multilayer analytical model. The inspection of two plates was conducted with linear arrays of piezoelectric transducers and synthetic aperture imaging techniques. The ultrasonic images of textile composite plates take into account the propagation mode, the dispersion compensation of the wave packet and ...