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Doctor of Philosophy / Department of Mechanical and Nuclear Engineering / Youqi Wang / Textile fabrics and textile composite materials demonstrate exceptional mechanical properties, including high stiffness, high strength to weight ratio, damage tolerance, chemical resistance, high temperature tolerance and low thermal expansion. Recent advances in weaving techniques have caused various textile fabrics to gain applications in high performance products, such as aircrafts frames, aircrafts engine blades, ballistic panels, helmets, aerospace components, racing car bodies, net-shape joints and blood vessels. Fabric mechanical properties are determined by fabric internal architectures and fabric micro-geometries are determined by the textile manufacturing process. As the need for high performance textile materials increases, textile preforms with improved thickness and more complex structures are designed and manufactured. Therefore, the study of textile fabrics requires a reliable and efficient CAD/CAM tool that models fabric micro-geometry through computer simulation and links the manufacturing process with fabric micro-geometry, mechanical properties and weavability. Dynamic Weaving Process Simulation is developed to simulate the entire textile process. It employs the digital element approach to simulate weaving actions, reed motion, boundary tension and fiber-to-fiber contact and friction. Dynamic Weaving Process Simulation models a Jacquard loom machine, in which the weaving process primarily consists of four steps: weft insertion, beating up, weaving and taking up. Dynamic Weaving Process Simulation simulates these steps according to the underlying loom kinematics and kinetics. First, a weft yarn moves to the fell position under displacement constraints, followed by a beating-up action performed by reed elements. Warp yarns then change positions according to the yarn interlacing pattern defined by a weaving matrix, and taking-up action is simulated to collect woven fabric for continuous weaving process simulation. A Jacquard loom machine individually controls each warp yarn for maximum flexibility of warp motion, managed by the weaving matrix in simulation. Constant boundary tension is implemented to simulate the spring at each warp end. In addition, process simulation adopts re-mesh function to store woven fabric and add new weft yarns for continuous weaving simulation. Dynamic Weaving Process Simulation fully models loom kinetics and kinematics involved in the weaving process. However, the step-by-step simulation of the 3D weaving process requires additional calculation time and computer resource. In order to promote simulation efficiency, enable finer yarn discretization and improve accuracy of fabric micro geometry, parallel computing is implemented in this research and efficiency promotion is presented in this dissertation. The Dynamic Weaving Process Simulation model links fabric micro-geometry with the manufacturing process, allowing determination of weavability of specific weaving pattern and process design. Effects of various weaving process parameters on fabric micro-geometry, fabric mechanical properties and weavability can be investigated with the simulation method.

The electro-kinetic characteristics of different material bioreactor columns for treating water and waste water are experimentally studied. Separate columns of unsaturated gravels (~6mm) and ball clay were assessed for electro-kinetic characteristics by dosing water at a hydraulic loading rate of 50ml/min and 10ml/min. Similarly locally available organic materials such as sawdust, Moringa oleifera sheets and textile clothe pieces were also empirically analyzed. Size effects of the bio-reactor columns were also studied. The effluent from textile clothe and gravel reactor respectively showed an increase in pH while a depreciation in pH in the effluent was observed in the Moringa Oleifera reactor and sawdust reactor. This may be due to leaching of acidic organic components for sawdust and Moringa Oleifera . In gravels effluent pH depreciated with increase in flow rate but the general trend of the effluent pH curve showed an initial improvement before it slowed down to an asymptote for a specific constant dosage and height. A multi-parameter stochastic linear model for change in pH as a function of column height, dosage rate, time for specific volume discharge and change in electrical conductivity between influent and effluent was derived. A general stochastic model was also developed to characterize pH change in any bioreactor irrespective of the material media. Thirty centimeters of gravel exhibited an increase in conductivity with increase in flow rate while conductivity dipped with increasing flow rate when the gravel column height was halved. The measure of organic compounds in water decreased with increasing percolation rate through gravel. The chemical oxygen demand ratio within the gravel improved to unity showing increased containment of organic compounds with time. Organic textile clothes reactor also illustrated increased conductivity with increasing flow but conductivity dipped with increase in column height. For Moringa Oleifera reactors, a dosage of water at 10ml/min showed a significant improvement in conductivity with increase in column height. An initial depreciation in temperature curve was observed within clay and gravel reactor. With increase in depth there was an increase in temperature within the gravel as the saturation by water improved. In sawdust reactors this was not the trend. A birth process model is proposed to simulated temperature within a bioreactor as a function of time irrespective of any specific material used as bioreactor media.

Understanding the interactions of polymer interfaces is essential to improve polymer-based designs, as the properties of the interface are often different than those of the bulk material. This thesis explores the interfacial interactions of polymer interfaces for two classes of materials, additive manufacturing materials and fiber-reinforced composites. Additive manufacturing (AM) refers to a number of processes which rely on data generated from computer-aided design (CAD) programs to construct components by adding material in a layer-by-layer fashion. AM continues to generate a substantial amount of interest to produce fully functional products while reducing tooling costs associated with traditional manufacturing techniques such as casting and welding. Recent advancements in the field have led to the production of multi-material printing that has the potential to create products with enhanced mechanical properties and additional functionality. This thesis attempts to characterize the fracture resistance of AM materials produced by the PolyJet process. Test standards established for mode I fracture testing of adhesive joints are adapted to evaluate the fracture resistance and interface between two printed acrylic-based photopolymers. Significant differences in fracture energy and loci of failure between the selected test configurations were observed depending on the print orientation. Failures were nominally seen to occur at the interface, alternating from one adherend interface to another in a random fashion. Results demonstrated a decreasing trend in fracture energy at slower crack propagation rates, indicating that such dependency is associated with the fracture resistance of the interface. T-peel tests conducted on specimens prepared with both constant and graded interlayers revealed enhanced peel resistance with gradient interlayers, suggesting design opportunities of enhanced fracture toughness by implementing intricate material patterns at the interface of the two photopolymers. Fiber reinforced composite (FRCs) materials have become increasingly desirable in a number of industrial applications where weight reduction is critical for increased payloads and higher performance. When manufacturing structures from these materials, the presence of friction in the composite forming process is seen to have a major effect on the finished quality. Friction between the plies, or between the composite laminate and forming tool, can be undesirable as shape distortions such as wrinkles can appear and compromise the structural integrity of the finished product. To evaluate these frictional processes, a standard rheometer is used to evaluate tool-ply friction on dry textile fabrics and graphite/epoxy prepregs over a range of temperatures, pressures, and sliding velocities. The results provide some general insights into the frictional response of composite prepregs as a function of the manufacturing environment. The materials tested are shown to have different mechanisms that govern the frictional processes. In particular, the results of friction testing on the prepreg indicate that friction comes from a contribution of both Coulomb and viscous-related mechanisms, the latter which become especially at higher temperatures. / Master of Science

[ES] En este trabajo de Tesis se han llevado a cabo cuatro líneas de investigación a fin de analizar el comportamiento acústico de nuevas soluciones basadas en tejidos textiles procedentes de la industria textil, a partir de modificaciones o combinaciones estructurales de los mismos. En esta Tesis se ha estudiado la estructura de la fibra textil a partir del análisis de los parámetros macroestructurales de la fibra, como la finura, la longitud, y la sección transversal. Además, se ha investigado el grado de influencia de estos parámetros sobre la absorción acústica. Se pudo evidenciar que la finura de la fibra tiene una influencia significativa en la absorción acústica en comparación con la longitud de fibra. Además, las fibras huecas tienen un mejor comportamiento acústico, comparado con las fibras sólidas. Una vez analizada la estructura y la composición de la fibra, se adhirieron microcápsulas en la superficie de los tejidos textiles a fin de aumentar la absorción acústica de éstos. Para ello, se han considerado distintas posibilidades de diseño según el tipo de tejido base usado, la homogeneidad de los tejidos de base dopada y la concentración de microcápsulas. Además, se ha utilizado un modelo de membrana con la finalidad de predecir el comportamiento acústico de tejidos textiles dopados con microcápsulas. En este estudio se pudo comprobar que la absorción acústica está influenciada por el dopaje de los tejidos con MCCs. Seguidamente, se combinaron tejidos textiles con con otros materiales con el objetivo de disponer de absorción selectiva o de aumentar la absorción acústica en el rango de frecuencias de trabajo. Asimismo, se ha pretendido observar el efecto acústico de espumas tradicionales perforadas mediante diferentes tecnologías. Además, se han utilizado modelos de doble porosidad y métodos numéricos con la finalidad de validar los resultados obtenidos experimentalmente. Se pudo comprobar que la absorción acústica del sistema tejido-espuma perforada depende ligeramente del textil usado. Además, se obtuvo gran concordancia entre los valores predichos y experimentales. Finalmente, se ha analizado la influencia de la estructura del tejido. Se ha investigado el efecto acústico producido por los parámetros geométricos, utilizados en el diseño de tejidos plegados, como la longitud del pliegue, el número de pliegues, la distancia entre pliegues consecutivos o la altura del pliegue. Se ha pretendido, mediante cambios en la estructura del tejido textil, obtener valores de absorción típicos de un material acústico. Además, se ha utilizado un modelo de membrana permeable plegada con el fin de predecir el coeficiente de absorción acústica en campo difuso. En este estudio se pudo comprobar que los tejidos plegados presentan un mayor coeficiente de absorción acústica en medias y altas frecuencias, tanto en incidencia normal como en incidencia aleatoria. Además, a menor número de pliegues, se consiguen valores más elevados de absorción acústica en todo el margen frecuencial. / [CA] En aquest treball de Tesi s'han dut a terme quatre línies de recerca per tal d'analitzar el comportament acústic de noves solucions basades en teixits tèxtils procedents de la indústria tèxtil, a partir de modificacions o combinacions estructurals dels mateixos. En aquesta Tesi s'ha estudiat l'estructura de la fibra tèxtil a partir de l'anàlisi dels paràmetres macroestructurals de la fibra, com la finor, la longitud, i la secció transversal. A més a més, s'ha investigat el grau d'influència d'aquests paràmetres sobre l'absorció acústica. Es va poder evidenciar que la finor de la fibra té una influència significativa en l'absorció acústica en comparació amb la longitud de fibra. A més, les fibres buides tenen un millor comportament acústic, comparat amb les fibres sòlides. Una volta analitzada l'estructura i la composició de la fibra, es van adherir microcàpsules en la superfície dels teixits tèxtils a fi d'augmentar l'absorció acústica d'aquests. Per a això, s'han considerat diferents possibilitats de disseny segons el tipus de teixit bàsic emprat, l'homogeneïtat dels teixits de base dopada i la concentració de microcàpsules. A més a més, s'ha utilitzat un model de membrana amb la finalitat de predir el comportament acústic de teixits tèxtils dopats amb microcàpsules. En aquest estudi es va comprovar que l'absorció acústica està influenciada pel dopatge dels teixits amb MCCs. Seguidament, es van combinar teixits tèxtils amb amb altres materials amb l'objectiu de disposar d'absorció selectiva o d'augmentar l'absorció acústica en el rang de freqüències de treball. Així mateix, s'ha pretès observar l'efecte acústic d'espumes tradicionals perforades mitjançant diferents tecnologies. A més a més, s'han utilitzat models de doble porositat i mètodes numèrics amb la finalitat de validar els resultats obtinguts experimentalment. Es va comprovar que l'absorció acústica de sistema teixit-espuma perforada depèn lleugerament del tèxtil usat. A més, es va obtenir gran concordança entre els valors predits i experimentals. Finalment, s'ha analitzat la influència de l'estructura del teixit. S'ha investigat l'efecte acústic produït pels paràmetres geomètrics, utilitzats en el disseny de teixits plegats, com la longitud del plec, el nombre de plecs, la distància entre plecs consecutius o l'alçada del plec. S'ha pretès, mitjançant canvis en l'estructura del teixit tèxtil, obtenir valors d'absorció típics d'un material acústic. A més a més, s'ha utilitzat un model de membrana permeable plegada per tal de predir el coeficient d'absorció acústica en camp difús. En aquest estudi es va poder comprovar que els teixits plegats presenten un major coeficient d'absorció acústica en mitges i altes freqüències, tant en incidència normal com en incidència aleatòria. A més, a menor nombre de plecs, s'aconsegueixen valors més elevats d'absorció acústica en tot el marge freqüencial. / [EN] In this thesis work, four lines of research have been carried out in order to analyse the acoustic behaviour of new solutions based on textile fabrics from the textile industry. In this Thesis, the structure of the textile fibre has been studied from the analysis of the macrostructural parameters of the fibre, such as fineness, length, and cross section. Furthermore, the degree of influence of these parameters on acoustic absorption has been investigated. It could be shown that the fineness of the fibre has a significant influence on the acoustic absorption compared to the length of the fibre. In addition, hollow fibres have a better acoustic behaviour, compared to solid fibres. Once the structure and composition of the fibre had been analysed, microcapsules were adhered to the surface of the textile fabrics to increase their acoustic absorption. For this, different design possibilities have been considered according to the type of base fabric used, the homogeneity of the doped base fabrics and the concentration of microcapsules. In addition, a membrane model has been used to predict the acoustic behaviour of textile fabrics doped with microcapsules. In this study it was found that acoustic absorption is influenced by fabric doping with MCCs. Then, textile fabrics were combined with other materials in order to have selective absorption or to increase acoustic absorption in the range of working frequencies. In the same way, it has been tried to observe the acoustic effect of traditional foams perforated with different technologies. In addition, double porosity models and numerical methods have been used to validate the results obtained experimentally. It was found that the acoustic absorption of the perforated fabric-foam system depends slightly on the textile used. In addition, great agreement was obtained between the predicted and experimental values. Finally, the influence of the fabric structure has been analysed. The acoustic effect produced by the geometric parameters used in the design of folded fabrics, such as the length of the fold, the number of folds, the distance between consecutive folds or the height of the fold has been investigated. It has been tried to obtain typical absorption values of an acoustic material through changes in the structure of the textile fabric. Furthermore, a folded permeable membrane model has been used to predict the acoustic absorption coefficient in diffuse field. In this study, it was found that folded fabrics have a higher acoustic absorption coefficient in medium and high frequencies, both in normal incidence and in random incidence. Furthermore, the fewer the folds, the higher the acoustic absorption values are achieved throughout the frequency range. / Atiénzar Navarro, R. (2021). Estudio, modelado y caracterización acústica de nuevas soluciones en base a tejidos textiles [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/166795