Examinando por Materia "Mechanical performance"
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Ítem The influence of electrospinning parameters and solvent selection on the morphology and diameter of polyimide nanofibers(Elsevier Ltd, 2018-03-01) Lasprilla-Botero; J.; Álvarez-Láinez; M.; Lagaron; J.M.; Universidad EAFIT. Departamento de Ingeniería de Diseño; Ingeniería de Diseño (GRID)Polyimide (PI) fibers display excellent thermal and mechanical performance; they have been recently investigated to fabricate hydrophobic membranes (mats) for high-performance applications. We studied the effect of electrospinning processing parameters and solvent selection on the morphology and the diameter of PI fibers. 11 different solvents and 22 solvent systems able to dissolve PI were located in a Teas graph with the aim of building the solubility-electrospinnability map for this material. PI solutions prepared with various solvents were electrospun at different electrospinning process parameters according to a 34–1 fractional factorial design of experiments. Polymer concentration and applied voltage were the most significant factors to create thin and uniform fibers. More homogeneous fibers and reproducible electrospinning process were obtained by using polymer concentrations above 15 wt%. However, all solutions showed different morphological evolution according to the solvents used. Based on the solubility–spinnability region settled for this PI, non-woven mats were obtained with rough surface fiber morphology and high water contact angle, suitable for applications such as hydrophobic membranes for oil-water separation. © 2017 Elsevier LtdÍtem PTFE as a toughness modifier of high-performance PEI/PBT blends: Morphology control during melt processing(John Wiley and Sons Ltd, 2021-02-01) Vásquez-Rendón M.; Álvarez-Láinez M.L.; Universidad EAFIT. Departamento de Ingeniería de Diseño; Ingeniería de Diseño (GRID)High-performance PEI/PBT blends are brittle because of phase distribution and blends densification. New morphologies developed by adding PTFE to PEI matrix during melt processing favor the toughness improvement of PEI/PBT blends. Ternary PEI/PBT/PTFE processability is not compromised by PTFE addition, and miscibility study by modulated differential scanning calorimetry and harmonic mean method shows that PTFE does not interfere with PEI and PBT interaction. Dual-phase and spore-like morphologies are formed for both PEI/PBT and PEI/PBT/PTFE blends, and they strongly influenced their mechanical performance. Although tensile strength of ternary blends does not decrease by PTFE addition, elongation at break deteriorates for blends with PEI concentrations <70 wt%. Nevertheless, blends with 80 wt% increase their ductility, and a synergic effect is observed in impact resistance results. PTFE acts as an impact modifier of PEI/PBT blends due to its distribution in the PEI matrix as debonded spheres and nanoparticles well-embedded in PEI matrix. © 2020 John Wiley & Sons LtdÍtem Structural diagnosis of rail vehicles and method for redesign(Polish Society of Technical Diagnostics, 2014-01-01) Aristizabal, M.; Barbosa, J.L.; Betancur, G.R.; Castañeda, L.F.; Zóltowski, B.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Estudios en Mantenimiento (GEMI)Structures of rail vehicles are designed for a useful structural life of 30 years. However, structural problems which reduce the mechanical performance of the structure might appear due to normal operation conditions, in some cases, make it unsuitable for a safe operation. This document presents the structural diagnosis of a metro system and the method for the redesign of structural elements of rail vehicles that was derived from this diagnosis, so that the structural performance of both the element and the whole structure is improved. It is based on the European standards related with aluminium and railway applications, and considers the necessary aspects to produce a safe solution for the final design.