Flores-Bonano, Sugeily

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    Tortuosity index based on dynamic mechanical properties of polyimide foam for aerospace application
    (2014) Flores-Bonano, Sugeily; Suárez, O. Marcelo; College of Engineering; Silva Araya, Walter; Quintero, Pedro; Valentín, Ricky; Department of Mechanical Engineering; Colón, Omar
    The aerospace industry has focused on the development of high performance polyimide foams because these materials are known for their thermal and acoustic insulation properties. Tortuosity is defined as a parameter that describes such thermal and acoustic insulation capacity as related to its absorption capacity. The determination of a reliable tortuosity index is lacking on the aerospace industry, therefore a methodology is formulated via direct and indirect characterization methods of a fluidfilled porous media. Biot parameters that describe the interaction of the solid phase and the fluid phase are correlated with the tortuosity. In this investigation, a chemical, thermal, and mechanical characterization was performed to the PolyuMACTM polyimide foam. The tortuosity of this material is measured considering a pressure difference as the resistivity variable, rather than electrical resistivity or molecular diffusivity as proposed on previous models. The present analysis is focused on an empirical establishment of the tortuosity index considering the correlation among hydraulic and structural dimensionless parameters obtained through the Buckingham’s Pi theorem. The behavior of the polyimide was studied for samples of different lengths compressed at 30%, 60%, and 90% from its original length on the foaming direction. It was found that factors such as porosity, length of the sample, and viscosity of the fluid are relevant considerations on the insulation performance of the material. Regression analysis produced a significant statistical model fit to the data correlated from the dimensionless parameters for each dynamic compression series.
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    Tortuosity index based on dynamic mechanical properties of polyimide foam for aerospace applications
    (MDPI, 2019-06-07) Flores-Bonano, Sugeily; Vargas-Martinez, Juan C.; Suárez, O. Marcelo; Silva-Araya, Walter; College of Engineering; Department of Materials Science and Engineering
    The determination of a reliable tortuosity index is lacking in the aerospace industry. Therefore, a methodology is formulated via direct and indirect characterization methods of a fluid-filled porous media. Chemical, thermal, and mechanical characterization was performed to the PolyuMAC(TM) polyimide foam. Tortuosity was measured considering a pressure difference as the resistivity variable, rather than electrical resistivity or molecular diffusivity, as proposed on previous models. This is an empirical establishment of the tortuosity index considering the correlation among hydraulic and structural dimensionless parameters obtained through the Buckingham’s Pi theorem. The behavior of the polyimide was studied for samples of different lengths compressed at 30%, 60%, and 90% of its original length on the foaming direction. Results show that, porosity, sample length, and fluid viscosity are relevant for the insulation performance of the material. Regression analysis produced a significant statistical model fit to the data correlated from the dimensionless parameters for each dynamic compression series.