Characterization of microcellular plastics for weight reduction in automotive interior parts

The present PhD thesis is framed within the Industrial Doctorate Plan promoted by the Generalitat de Catalunya and has been developed in cooperation between the Universitat Politècnica de Catalunya-BarcelonaTech, the Centre Català del Plàstic, SEAT SA and Volkswagen AG. The research project has as main objective the characterization of microcellular plastics obtained by injection molding, motivated by a concern to reduce weight, cost and carbon footprint in automotive plastic parts. First, cylindrical bars and square plates made of Acrylonitrile-Butadiene-Styrene (ABS) and 20% Glass Fiber reinforced-Polypropylene (PP 20GF) were injection molded and foamed through the MuCell® technology. Shot volume was found as the most influencing parameter on cell structure and tensile and flexural properties. The effect of mold temperature and injection speed was secondary and not statistically significant for the mechanical performance. Tensile and flexural properties decreased almost linearly with the apparent density, whereas impact resistance was strongly reduced during foaming. Glass fibers contributed to partially overcome the loss of properties due to the reduction in density. Cells act as crack arrestors by blunting the crack tip. However, once the crack is propagating, cells acting as stress concentrators lead to a decrease in fracture toughness. Because of the low amount of blowing agent injected during the foaming process, no significant changes in the thermal properties were determined as compared to that of the solid counterpart. Simulation of the microcellular injection molding process with Moldex 3D® software and prediction models of the mechanical properties based on the apparent density and morphological characteristics provided a good approach to the experimental results. On the other hand, the Core Back tool technology was also employed in this study. By pulling the core and increasing the final thickness of the part, the apparent density decreased but the bending stiffness was greatly enhanced. Finally, a new alternative foaming technology, called IQ Foam® and developed by Volkswagen AG, was used to produce rectangular plates and compare their properties to that of the obtained by MuCell® process. By using a minimum amount of blowing agent, foamed plastic parts through IQ Foam® obtained through this process exhibited thicker solid skins and lower cell densities, but consequently higher mechanical properties. Additional benefits such as cost-effectiveness, easy-to-use and machine-independence are also offered by this new emerging technology.La presente tesis doctoral se enmarca dentro del Plan de Doctorats Industrials convocado por la Generalitat de Catalunya y se ha desarrollado como colaboración entre la Universitat Politècnica de Catalunya-BarcelonaTech, el Centre Català del Plàstic, SEAT SA y Volkswagen AG. El proyecto de investigación tiene como principal objetivo la caracterización de plásticos microcelulares, motivado por el interés en reducir peso, coste e impacto ambiental en piezas de plástico de automoción. En primer lugar, se obtuvieron mediante moldeo por inyección barras cilíndricas y placas cuadradas fabricadas con Acrilonitrilo-Butadieno-Estireno (ABS) y Polipropileno reforzado con un 20% de fibra de vidrio (PP 20GF), espumadas con la tecnología MuCell®. El volumen de dosificación es el parámetro más influyente sobre la estructura celular y las propiedades a tracción y a flexión. El efecto de la temperatura de molde y velocidad de inyección, en cambio, es secundario y no introduce variaciones estadísticamente significativas sobre el rendimiento mecánico. Las propiedades a tracción y flexión se reducen de manera prácticamente lineal con la disminución de densidad, mientras que la resistencia a impacto decrece drásticamente debido a la espumación. El efecto reforzante de las fibras de vidrio contribuye a compensar parcialmente la caída de propiedades debido a la reducción de densidad. Las celdas tienden a enromar el frente de grieta, retrasando así el inicio de propagación. Sin embargo, una vez la grieta comienza a propagar, las celdas actúan como concentradores de tensión provocando una disminución en la tenacidad a fractura. El reducido contenido de agente espumante inyectado durante el proceso de espumación no es suficiente para producir cambios en las propiedades térmicas en comparación con las del material macizo. La simulación del proceso de inyección microcelular con el software Moldex 3D® y los modelos de predicción de propiedades mecánicas basados en la densidad y características morfológicas proporcionaron valores cercanos a los obtenidos experimentalmente. Por otro lado, en este trabajo también se estudió el efecto de la tecnología de molde Core Back en combinación con el proceso de espumado mediante moldeo por inyección. A través del movimiento de la cavidad y el aumento del espesor final de la pieza inyectada, la densidad aparente se reduce al mismo tiempo que la rigidez a flexión se incrementa considerablemente. Finalmente, una nueva tecnología de espumación desarrollada por Volkswagen AG, llamada IQ Foam®, se utilizó para la inyección de placas rectangulares y la comparación de sus propiedades con las de placas análogas obtenidas mediante el proceso MuCell®. Mediante la utilización de un contenido mínimo de agente espumante, las placas espumadas con IQ Foam® exhibieron mayores espesores de piel y menores densidades celulares, y por tanto, propiedades mecánicas ligeramente superiores. Esta nueva tecnología ofrece también otras ventajas, como una menor inversión inicial, facilidad de operación y posibilidad de utilización en cualquier máquina de inyección convencional

Mejora del modelo de interacción dinámica pantógrafo-catenaria

[EN] The main objective of this Master’s Thesis is the development of a dynamical interaction simulation model between pantograph and catenary in high speed lines by means of the finite element method. The formulation of new elements has been carried out considering the existing methodology for calculating the initial configuration of the catenary and analyzing the dynamical performance in service, developed by the Department of Mechanical Engineering and Materials at the Universitat Politècnica de València. This work complements the aforementioned in order to consider more realistic static and dynamic effects due to other elements contained in the catenary system. Firstly, the formulation of the element used to model the messenger and contact wires has been modified so as to take into account lacks of continuity because of connections with other elements. On the other hand, the messenger wire suspension and the tensioning system have been modeled by means of springs, dampers and equivalent masses. Secondly, new pantographs models have been developed, including degrees of freedom of rotation of some components. Moreover, a catenary-several pantographs interaction simulating method has been programmed, on the basis of a rising distance of the pantographs to the height of the contact wire. Finally, the code developed in this project has been used in order to compare results obtained in a reference catenary simulation defined by an international group of research institutions, like the Vehicle Technology Research Centre of the Universitat Politècnica de València.[ES] El presente Trabajo Fin de Máster tiene como objetivo principal el desarrollo de un modelo de simulación de la interacción dinámica entre pantógrafo y catenaria en líneas de alta velocidad mediante el método de los elementos finitos. La formulación de nuevos elementos se ha llevado a cabo considerando la metodología para el cálculo de la configuración inicial de la catenaria y su posterior análisis del comportamiento dinámico en servicio desarrollada en el Departamento de Ingeniería Mecánica y Materiales de la Universitat Politècnica de València. El trabajo desarrollado complementa pues al anteriormente citado para representar efectos estáticos y dinámicos más realistas debidos a diversos elementos presentes en el sistema que forma la catenaria. En primer lugar, se ha modificado la formulación del elemento tipo cable, empleado para modelar el cable sustentador y de contacto, con el fin de considerar la no continuidad producida cuando éste se conecta con otros elementos. Por otro lado, se ha representado el soporte del cable sustentador y el sistema de compensación mecánica mediante un conjunto de resortes, amortiguadores y masas equivalentes. A continuación, se han desarrollado modelos de pantógrafos con grados de libertad adicionales que consideran la rotación de algunos componentes. Asimismo, se ha implementado una metodología para la simulación de la interacción entre la catenaria y más de un pantógrafo. Por último, el código implementado se ha utilizado para comparar los resultados obtenidos en la simulación de una catenaria de referencia definida por un conjunto internacional de grupos de investigación, entre los que se encuentra el Centro de Investigación de Tecnología de Vehículos de la Universitat Politècnica de València.[CA] El present Treball Fi de Máster té com a objectiu principal el desenvolupament d’un model de simulació de la interacció dinàmica entre pantògraf i catenària en línies d’alta velocitat mitjançant el mètode dels elements finits. La formulació de nous elements s’ha dut a terme considerant la metodologia per al càlcul de la configuració inicial de la catenària i el seu posterior anàlisi del comportament dinàmic en servei desenvolupat al Departament d’Enginyeria Mecànica i Materials de la Universitat Politècnica de València. El treball desenvolupat complementa a l’anteriorment esmentat per a representar efectes estàtics i dinàmics més realistes deguts a diversos elements presents al sistema que forma la catenària. Per una part, s’ha modificat la formulació de l’element tipus cable, empleat per a modelar el cable sustentador i de contacte, per a considerar la no continuïtat produïda quan aquest es connecta amb altres elements. Per altre costat, s’ha representat el suport del cable sustentador i el sistema de compensació mecànica mitjançant un conjunt de ressorts, amortidors i masses equivalents. A continuació, s’han desenvolupat models de pantògrafs amb graus de llibertat que consideren la rotació d’alguns components. Així mateix, s’ha implementat una metodologia per a la simulació de la interacció entre la catenària i més d’un pantògraf. Per últim, el codi obtingut s’ha utilitzat per a comparar els resultats obtinguts en la simulació d’una catenària de referencia definida per un conjunt internacional de grups d’investigació, entre els quals es troba el Centre d’Investigació de Tecnologia de Vehicles de la Universitat Politècnica de València.Gómez Monterde, J. (2013). Mejora del modelo de interacción dinámica pantógrafo-catenaria. http://hdl.handle.net/10251/39138Archivo delegad

Morphology and mechanical characterization of ABS foamed by microcellular injection molding

In the present work ABS was used to inject cylindrical test bars, obtaining solid and foamed specimens. By varying the gas content, two levels of weight reduction were achieved. Morphology analysis revealed the presence of solid skin-foamed core structure in foamed samples. SEM micrographs showed a nucleus zone having bigger cells and irregular cell distribution, surrounded by a microcellular area with finer cell structure. Foamed bars with 10% and 17% of weight reduction presented similar values of cell size, cell density and solid skin thickness. On the other hand, results provided by simulation software were consistent with the experimental analysis. Mechanical properties were determined through tensile tests. Tensile strength and elastic modulus gradually decreased with decreasing apparent density. Experimental results were related to relative density and morphology parameters, and prediction models were employed to compare the estimated values to the experimental data.Peer ReviewedPostprint (published version

Effect of microcellular foaming on the fracture behavior of ABS polymer

In this work, the properties of microcellular ABS were studied. Foamed samples exhibited a solid skin/foamed core struc- ture, with some elongated cells in the flow direction, while spherical cells were mostly observed in the transversal direction. The flex- ural modulus, flexural strength, and fracture toughness K Ic decreased with the density. However, the crack tip opening displacement (CTOD) was found to increase with the foaming ratio. The evolution of the mechanical properties and fracture toughness was well described by prediction models considering the skin/core morphology of these microcellular materials. Foaming increased the aniso- tropic behavior of the material, due to the cell elongation caused by the fountain flow during injectionPeer ReviewedPostprint (author's final draft

ARID2 deficiency promotes tumor progression and is associated with higher sensitivity to chemotherapy in lung cancer

The survival rate in lung cancer remains stubbornly low and there is an urgent need for the identification of new therapeutic targets. In the last decade, several members of the SWI/SNF chromatin remodeling complexes have been described altered in different tumor types. Nevertheless, the precise mechanisms of their impact on cancer progression, as well as the application of this knowledge to cancer patient management are largely unknown. In this study, we performed targeted sequencing of a cohort of lung cancer patients on genes involved in chromatin structure. In addition, we studied at the protein level the expression of these genes in cancer samples and performed functional experiments to identify the molecular mechanisms linking alterations of chromatin remodeling genes and tumor development. Remarkably, we found that 20% of lung cancer patients show ARID2 protein loss, partially explained by the presence of ARID2 mutations. In addition, we showed that ARID2 deficiency provokes profound chromatin structural changes altering cell transcriptional programs, which bolsters the proliferative and metastatic potential of the cells both in vitro and in vivo. Moreover, we demonstrated that ARID2 deficiency impairs DNA repair, enhancing the sensitivity of the cells to DNA-damaging agents. Our findings support that ARID2 is a bona fide tumor suppressor gene in lung cancer that may be exploited therapeutically.Financial Support: I. V. is supported by SAF2012-31627 and SAF2016-76758-R grants from the Spanish Ministerio de Economía y Competitividad (MINECO), by a Fundación Ramón Areces grant and by ERC2014-StG637904 grant from the European Research Council. I. V has been awardee of the Programa Ramón y Cajal (MINECO, Spain). T. M has been awardee of the Ayudas para la contratación de investigadores predoctorales (MINECO, Spain). B. M is awardee of the Ayudas para la formación de profesorado universitario (FPU, Ministerio de Educación y Formación Profesional, Spain). PC laboratory is supported by grant SAF-2015-63638R (MINECO/FEDER, UE); by Centro de Investigación Biomédica en Red de Cáncer (CIBERONC) and by Asociación Española Contra el Cáncer (AECC), grant GCB141423113. BC has been supported by a Retos Jóvenes Investigadores grant SAF2015-73364-JIN (AEI/FEDER, UE) and a grant from Fundación Francisco Cobos. P. S. is supported by the Francis Crick Institute, which receives its core funding from Cancer Research UK (FC001152), the UK Medical Research Council (FC001152). HUCA/IUOPA which is jointly financed by Servicio de Salud del Principado de Asturias, Instituto de Salud Carlos III and Fundación Bancaria Cajastur. This research was funded in part by the Wellcome Trust [FC001152]

Simulación dinámica de la interacción pantógrafo-catenaria mediante elementos finitos

Proyecto confidencialGómez Monterde, J. (2012). Simulación dinámica de la interacción pantógrafo-catenaria mediante elementos finitos. http://hdl.handle.net/10251/28300.Archivo delegad

Morphology and mechanical characterization of ABS foamed by microcellular injection moulding

In the present work ABS was used to inject cylindrical test bars, obtaining solid and foamed especimens. By varying the gas content, two levels of weight reduction were achieved. Morphology analysis revealed the presence of solid skin-foamed core structure in foamed samples. SEM micrographs showed a nucleus zone having bigger cells and irregular cell distribution surrounded by a microcellular area with finer cell structure. Foamed bars with 10% and 17% of weight reduction presented similar values of cell size, cell density and solid skin thickness. On the other hand, results provided by simulation software were consistent with the experimental analysis. Mechanical properties were determined throught tensile tests. Tensile strength and elastic modulus gradually decreased with decreasing apparent density. Experimental results were related to relative density and morphology parameters, and prediction models were employed to compare the estimated values to the experimental data.Postprint (published version

Morphology and mechanical characterization of ABS foamed by microcellular injection molding

In the present work ABS was used to inject cylindrical test bars, obtaining solid and foamed specimens. By varying the gas content, two levels of weight reduction were achieved. Morphology analysis revealed the presence of solid skin-foamed core structure in foamed samples. SEM micrographs showed a nucleus zone having bigger cells and irregular cell distribution, surrounded by a microcellular area with finer cell structure. Foamed bars with 10% and 17% of weight reduction presented similar values of cell size, cell density and solid skin thickness. On the other hand, results provided by simulation software were consistent with the experimental analysis. Mechanical properties were determined through tensile tests. Tensile strength and elastic modulus gradually decreased with decreasing apparent density. Experimental results were related to relative density and morphology parameters, and prediction models were employed to compare the estimated values to the experimental data.Peer Reviewe

Morphology and mechanical characterization of ABS foamed by microcellular injection moulding

In the present work ABS was used to inject cylindrical test bars, obtaining solid and foamed especimens. By varying the gas content, two levels of weight reduction were achieved. Morphology analysis revealed the presence of solid skin-foamed core structure in foamed samples. SEM micrographs showed a nucleus zone having bigger cells and irregular cell distribution surrounded by a microcellular area with finer cell structure. Foamed bars with 10% and 17% of weight reduction presented similar values of cell size, cell density and solid skin thickness. On the other hand, results provided by simulation software were consistent with the experimental analysis. Mechanical properties were determined throught tensile tests. Tensile strength and elastic modulus gradually decreased with decreasing apparent density. Experimental results were related to relative density and morphology parameters, and prediction models were employed to compare the estimated values to the experimental data

Effect of microcellular foaming on the fracture behavior of ABS polymer

In this work, the properties of microcellular ABS were studied. Foamed samples exhibited a solid skin/foamed core struc- ture, with some elongated cells in the flow direction, while spherical cells were mostly observed in the transversal direction. The flex- ural modulus, flexural strength, and fracture toughness K Ic decreased with the density. However, the crack tip opening displacement (CTOD) was found to increase with the foaming ratio. The evolution of the mechanical properties and fracture toughness was well described by prediction models considering the skin/core morphology of these microcellular materials. Foaming increased the aniso- tropic behavior of the material, due to the cell elongation caused by the fountain flow during injectionPeer Reviewe