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In this work some theoretical aspects of constitutive equations for thixotropic fluids and restrictions on their functional forms are formally discussed. In the current study a formal emphasis has been given to the structural nature of this substances. The behavior of thixotropic fluids is analyzed in terms of simple isothermal laminar shear flow.

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The present work describes an investigation into a vibro-acoustic method to check the existence of superficial flaws in composite sandwich structures, based in a technique inspired in the well known Tap Test. In this case, however, a non-impulsive excitation is provided by an especial transducer and the acoustic response is captured with a microphone. A deconvolution technique is used in order to assess the system's impulse response and generate a “failure” map after post-processing the results. Post-processed parameters evaluated are: Loudness, Sharpness and a discrepancy indicator for the transfer function (named TFDI). Results suggest that Loudness and TFDI potentially indicate the existence of a damaged core and the lack of adhesive tape.