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    Fracture toughness reliability in polycarbonate: notch sharpening effects  Open access

     Salazar López, Alicia; Rodríguez Pérez, Jesús; Martinez Benasat, Antonio
    Indian Journal of Materials Science
    Date of publication: 2014-01-06
    Journal article

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    The effect of the notch sharpening on the fracture toughness obtained under linear elastic fracture mechanics has been analyzed in an amorphous polycarbonate. The samples for fracture characterization were sharpened via the traditional contact steel razor blade technique and the noncontact femtosecond laser ablation technique. The values of the fracture toughness of the specimens sharpened through femtosecond laser ablation were lower than those measured on samples sharpened using a steel razor blade. Moreover, the former was in plane strain state, but the latter did not verify the size criterion. The damage produced ahead of the crack tip through plastic deformation in the steel razor blade sharpened samples over the lack of damage in the femtolaser sharpened specimens explains the differences in the fracture toughness. It has been proven that there is a relationship between the plastic deformation at the crack front and the stress state. This has been assessed through the application of a fracture criterion for dissipative systems with small scale yielding.

    The effect of the notch sharpening on the fracture toughness obtained under linear elastic fracture mechanics has been analyzed in an amorphous polycarbonate. The samples for fracture characterization were sharpened via the traditional contact steel razor blade technique and the noncontact femtosecond laser ablation technique. The values of the fracture toughness of the specimens sharpened through femtosecond laser ablation were lower than those measured on samples sharpened using a steel razor blade. Moreover, the former was in plane strain state, but the latter did not verify the size criterion. The damage produced ahead of the crack tip through plastic deformation in the steel razor blade sharpened samples over the lack of damage in the femtolaser sharpened specimens explains the differences in the fracture toughness. It has been proven that there is a relationship between the plastic deformation at the crack front and the stress state. This has been assessed through the application of a fracture criterion for dissipative systems with small scale yielding

  • Influence of the notch sharpening on the impact fracture toughness of ethylene-propylene block copolymers

     Martinez Benasat, Antonio; Arencón Osuna, David; Rodríguez Pérez, Jesús; Salazar López, Alicia
    Polymer testing
    Date of publication: 2014-06-01
    Journal article

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    The impact fracture toughness of several ethylene-propylene block copolymers has been evaluated using the traditional contact notch sharpening technique of tapping and a new non-contact technique based on femtolaser ablation. The fracture toughness values obtained with the specimens notched by the femtolaser ablation technique were always lower than the tapped specimens. The impact fracture toughness values of these block copolymers does not depend only on the ethylene content, but also the molecular weight has a remarkable influence. © 2014 Elsevier Ltd. All rights reserved.

    The impact fracture toughness of several ethylene-propylene block copolymers has been evaluated using the traditional contact notch sharpening technique of tapping and a new non-contact technique based on femtolaser ablation. The fracture toughness values obtained with the specimens notched by the femtolaser ablation technique were always lower than the tapped specimens. The impact fracture toughness values of these block copolymers does not depend only on the ethylene content, but also the molecular weight has a remarkable influence. © 2014 Elsevier Ltd. All rights reserved.

  • Fractura de films poliméricos

     Martinez Benasat, Antonio; Arencón Osuna, David; Illescas Fernandez, Silvia
    Encuentro del Grupo Español de Fractura
    Presentation's date: 2014-04-03
    Presentation of work at congresses

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  • Nanocompuestos exfoliados de butilen tereftalato cíclico/arcilla obtenidos por polimerización in-situ

     Abt, Tobias Martin; Sanchez Soto, Miguel Angel; Martinez Benasat, Antonio; Illescas Fernandez, Silvia; Arencón Osuna, David
    Congreso Nacional de Materiales
    Presentation's date: 2014-06-18
    Presentation of work at congresses

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  • On the effect of the different notching techniques on the fracture toughness of PETG

     Martinez Benasat, Antonio; León, Noel; Arencón Osuna, David; Rodríguez Pérez, Jesús; Salazar López, Alicia
    Polymer testing
    Date of publication: 2013-10
    Journal article

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    The fracture toughness of poly (ethylene terephthalate) modified glycol (PETG) has been evaluated using notch sharpening techniques which could be grouped into contact and non-contact procedures. Razor blade tapping, razor blade sliding, razor pressing and broaching are part of the first group, while the femtolaser technique belongs to the second one. Not all the contact procedures generated valid sharp cracks for fracture parameter assessment; indeed none of the samples sharpened via razor sliding generated acceptable sharp cracks. The results revealed that the non-contact femtolaser technique produced the sharpest cracks in this polymer, with crack tip radii of only 0.5 µm, leading to the lowest fracture toughness values. On the contrary, the traditional notch sharpening technique based on razor tapping, recommended in ISO, ESIS and ASTM protocols and standards, generated larger crack tip radii than those introduced via femtolaser and, consequently, resulted in higher fracture toughness values. Both broaching and pressing methods created specimens with smaller crack tip radii compared to those obtained by razor tapping, and hence resulting in intermediate fracture toughness values

    The fracture toughness of poly (ethylene terephthalate) modified glycol (PETG) has been evaluated using notch sharpening techniques which could be grouped into contact and non-contact procedures. Razor blade tapping, razor blade sliding, razor pressing and broaching are part of the first group, while the femtolaser technique belongs to the second one. Not all the contact procedures generated valid sharp cracks for fracture parameter assessment; indeed none of the samples sharpened via razor sliding generated acceptable sharp cracks. The results revealed that the non-contact femtolaser technique produced the sharpest cracks in this polymer, with crack tip radii of only 0.5 μm, leading to the lowest fracture toughness values. On the contrary, the traditional notch sharpening technique based on razor tapping, recommended in ISO, ESIS and ASTM protocols and standards, generated larger crack tip radii than those introduced via femtolaser and, consequently, resulted in higher fracture toughness values. Both broaching and pressing methods created specimens with smaller crack tip radii compared to those obtained by razor tapping, and hence resulting in intermediate fracture toughness values.

  • Influence of the injection-molding parameters on the cellular structure and thermo-mechanical properties of ethylene-propylene block copolymer foams

     Gómez Gómez, Jaime Francisco; Arencón Osuna, David; Sanchez Soto, Miguel Angel; Martinez Benasat, Antonio
    Advances in polymer technology
    Date of publication: 2013-03
    Journal article

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    Microcellular injection-molding technology is capable of producing lightweight polymeric products. The foam morphology is determined by the injection-molding parameters, and it has been observed that depending on the parameter variations, the cell structure may exhibit substantial morphological differences through the entire section along the melt flow direction of the injected part. The effects of varying injection-molding parameters on foam morphology and thermal mechanical properties of a multiphase ethylene-propylene block copolymer (EPBC) were tested on 5-mm plaque specimens using a constant temperature profile. It has been found that injection speed does not have a significant effect on the thermal-mechanical properties of the foam, whereas shot volume and mold temperature do have a significant influence. Low shot volume produces uniform density cellular structures and larger cores, whereas lower mold temperatures help maintain small cell sizes. Furthermore, the effect of the copolymer’s crystalline phase on foam morphology has been observed. This study identifies the achievable foam morphologies and the thermal-mechanical performance of cellular molded EPBC parts.

  • Influence of the injection moulding parameters on the microstructure and thermal properties of microcellular polyethylene terephthalate glycol foams

     Gómez Gómez, Jaime Francisco; Arencón Osuna, David; Sanchez Soto, Miguel Angel; Martinez Benasat, Antonio
    Journal of cellular plastics
    Date of publication: 2013
    Journal article

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    Microcellular injection moulding is capable of producing lightweight polymeric products. The present study analyses the influence of several representative injection moulding parameters on the foam’s morphology, apparent density and thermo-mechanical properties of PETG, poly(ethylene terephthalate-co-1,4-cyclohexylene-dimethylene terephthalate) specimens. A strong variation of the cell morphology along the melt flow direction has been found, as well as a dependence on the shot volume. The most homogeneous microcellular structure is achieved when low shot volume, intermediate injection speed and low mould temperature are employed. The skin–core structure of the injected parts, determined the thermo-mechanical features of the specimen, which are ruled by the skin layer.

  • Experimental characterization and modelling of large-strain viscoelastic behavior of a thermoplastic polyurethane elastomer

     Bartolome, L.; Aginagalde, A.; Martinez Benasat, Antonio; Urchegi, M.A.; Tato, W.
    Rubber chemistry and technology
    Date of publication: 2013-01-14
    Journal article

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    hermoplastic polyurethane elastomers (TPUs) are a kind of elastomer that can be processed as thermoplastics. These elastomers exhibit a highly nonlinear behavior characterized by hyper-elastic deformability. Furthermore, the mechanical behavior of these elastomers is time-dependent, that is, they exhibit a viscoelastic behavior. We describe the material response of a TPU under moderate strains (epsilon < 1) by using an overlay visco-hyperelastic model assuming separation of time dependence from nonlinear stress-strain behavior. To achieve this goal, cyclic loading-unloading experimental tests are carried out for two homogeneous deformation states, uniaxial tension and pure shear, and the strain-stress data are then analyzed to fit a hyperelastic model. Conversely, a viscoelastic model is obtained from relaxation tests. Finally, the visco-hyperelastic model is implemented in a finite element calculation tool (ABAQUS), and the numerical results show a reasonable correlation with experimental data. As a result, a overlay visco-hyperelastic model depending on maximum strain is proposed.

  • The role of notch sharpening on the J-fracture toughness of thermoplastic polymers

     Salazar López, Alicia; Rodríguez Pérez, Jesús; Martinez Benasat, Antonio
    Engineering fracture mechanics
    Date of publication: 2013-04-02
    Journal article

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    The effect of the notch sharpening on the fracture toughness obtained under Elastic–Plastic Fracture Mechanics (EPFMs) approach has been analyzed in two different types of thermoplastic polymers, a semicrystalline multi-phase ethylene–propylene block copolymer and an amorphous polycarbonate. The samples for fracture characterization were sharpened using a steel razor blade and the femtosecond laser ablation technique. Both notching techniques gave rise to the very same size of crack tip radii, 1–2 μm. For all the materials under study, the fracture toughness values of the specimens sharpened through femtosecond laser ablation were lower than those measured on samples sharpened using a steel razor blade. The largest differences were achieved for the amorphous polycarbonate. The damage produced ahead of the crack tip through plastic deformation in the steel razor blade sharpened samples over against the lack of damage in the femtolaser sharpened specimens explains the disparity in the fracture values. Besides, the stress state ahead of the crack tip is closely related to the plastic deformation zone to specimen thickness ratio. The fracture toughness values determined from the femtolaser sharpened samples were all in plane strain conditions while the values of the fracture toughness obtained from the steel razor blade sharpened specimens were not.

  • Efecto de la agudización de la entalla en la determinación de los parámetros de la Mecánica de la Fractura de polímeros y compuestos con fibra corta

     Martinez Benasat, Antonio; Arencón Osuna, David; Rodríguez Pérez, Jesús; Salazar López, Alicia; Castillo, Germán
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  • Combined effects of sc-CO2 and graphene nanoparticles on the crystallinity of bisphenol A polycarbonate

     Gedler, Gabriel; de Sousa Pais Antunes, Marcelo; de Redondo Realinho, Vera Cristina; Martinez Benasat, Antonio; Velasco Perero, Jose Ignacio
    International Symposium Frontiers in Polymer Science
    Presentation's date: 2013-05-23
    Presentation of work at congresses

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    There is still lack of information regarding changes in the microstructure of polycarbonate (PC) due to the addition of secondary phases and processing. In this work, PC composites with graphene were expanded using supercritical CO2 (sc-CO2). Raman spectroscopy, XRD and DSC demonstrated that the presence of graphene and CO2 induced PC¿s crystallization during saturation. Double melting behavior indicated the presence of crystals with different thermal stabilities. Saturation temperature, time and CO2 pressure had a direct effect on PC's melting temperature, indicating that processing parameters may be regulated to achieve different crystalline microstructures. Raman spectroscopy enabled to correlate changes in PC¿s crystallinity with processing conditions, showing that graphene and sc-CO2 favored the formation of an ordered non-crystalline phase. This induced crystallization, combined with graphene, led to composites with specific moduli that were up to 15% higher than that of unfilled PC.

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    Caracterización mecánica, térmica y a fuego de aerogeles arcilla/polímero modificados con partículas  Open access

     Sanchez Soto, Miguel Angel; Wang, Liang; Martinez Benasat, Antonio; Velasco Perero, Jose Ignacio; Santana Pérez, Orlando Onofre; Maspoch Ruldua, Maria Lluïsa
    Congreso Nacional de Materiales Compuestos
    Presentation's date: 2013-07-03
    Presentation of work at congresses

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    Los aerogeles son una clase de materiales que se caracteriza por su extrema ligereza y alto contenido de aire. En este trabajo se han preparado diferentes aerogeles polímero/arcilla (PVOH/Na+-MMT) mediante un proceso simple de congelación y liofilización. Mediante esta técnica se han preparado aerogeles modificados conteniendo diferentes agentes ignifugantes en forma de partículas. La adición de dichos agentes causó un ligero incremento de la densidad aparente. Las propiedades mecánicas en compresión tanto a baja como a alta velocidad en general se vieron ligeramente reducidas debido a una menor unión entre el polímero y la arcilla. La excepción fue la muestra modificada con Al(OH)3 que incrementó la rigidez de los compuestos y la tensión a máxima deformación. En cuanto a las propiedades térmicas, la presencia de polifosfato de amonio (APP) o de silica gel (SG) redujo notablemente la velocidad de descomposición de los aerogeles en el rango de temperaturas entre 250ºC y 650ºC, sin embargo, la temperatura de inicio de descomposición no se vio sensiblemente alterada. El comportamiento a fuego se analizó mediante calorimetría de cono y los resultados han indicado que tanto la presencia de Al(OH)3 como de APP retardan la combustión del sistema y reducen la tasa de liberación de calor.

    Los aerogeles son una clase de materiales que se caracteriza por su extrema ligereza y alto contenido de aire. En este trabajo se han preparado diferentes aerogeles polímero/arcilla (PVOH/Na+-MMT) mediante un proceso simple de congelación y liofilización. Mediante esta técnica se han preparado aerogeles modificados conteniendo diferentes agentes ignifugantes en forma de partículas. La adición de dichos agentes causó un ligero incremento de la densidad aparente. Las propiedades mecánicas en compresión tanto a baja como a alta velocidad en general se vieron ligeramente reducidas debido a una menor unión entre el polímero y la arcilla. La excepción fue la muestra modificada con Al(OH)3 que incrementó la rigidez de los compuestos y la tensión a máxima deformación. En cuanto a las propiedades térmicas, la presencia de polifosfato de amonio (APP) o de silica gel (SG) redujo notablemente la velocidad de descomposición de los aerogeles en el rango de temperaturas entre 250ºC y 650ºC, sin embargo, la temperatura de inicio de descomposición no se vio sensiblemente alterada. El comportamiento a fuego se analizó mediante calorimetría de cono y los resultados han indicado que tanto la presencia de Al(OH)3 como de APP retardan la combustión del sistema y reducen la tasa de liberación de calor.

  • Influencia de la agudización de la entalla sobre los parámetros de la fractura de polímeros

     Martinez Benasat, Antonio; León, Noel; Arencón Osuna, David; Rodríguez Pérez, Jesús; Salazar López, Alicia
    Encuentro del Grupo Español de Fractura
    Presentation's date: 2013-03-14
    Presentation of work at congresses

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  • Problemas experimentales en la caracterización en fractura de materiales poliméricos

     Rodríguez Pérez, Jesús; Salazar López, Alicia; Martinez Benasat, Antonio
    Encuentro del Grupo Español de Fractura
    Presentation's date: 2013-03-15
    Presentation of work at congresses

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  • Determinación de las curvas tensión-deformación verdaderas en polímeros

     Maspoch Ruldua, Maria Lluïsa; Loaeza, David; Martinez Benasat, Antonio; Arencón Osuna, David; de Sousa Pais Antunes, Marcelo; Velasco Perero, Jose Ignacio
    Encuentro del Grupo Español de Fractura
    Presentation's date: 2013-03-14
    Presentation of work at congresses

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  • Films of native and modified starch reinforced with fiber: influence of some extrusion variabels using response surface methodology

     Galicia Garcia, Tomás; Martínez Bustos, F; Jiménez Arévalo, Omar; Arencón Osuna, David; Gámez Pérez, José; Martinez Benasat, Antonio
    Journal of applied polymer science
    Date of publication: 2012-10-25
    Journal article

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    Corn starch (native and phosphorylated) and potato films containing glycerol as plasticizer, and bagasse sugar cane as fiber, were produced by extrusion-calendering process, and characterized for the mechanical properties (tensile stress at rupture rr, elongation at break eb, and Young’s modulus E), water disintegration index (WDI), water absorption capacity (WAC), and luminosity. The evaluated processing variables were: feed moisture, fiber content, and type of starch. The response surface methodology was applied to analyze, and the model of significance was justified by a variance analysis (F-test). The inclusion of fiber provides a mechanical reinforcement to the starch matrix favoring the elongation at break (eb) in thickness films (280–350 lm). Samples formulated with potato starch within the values of feed moisture 18.25, 20.5, and 5 wt % of fiber content, showed an increment in values of tensile stress at rupture (3.80–4.4 MPa) and Young’s modulus (78.47–68.04 MPa). Corn starch films with high fiber content (10%) and low feed moisture (18.25%) values showed a decrement in elongation at break (12.93%). WAC and WDI were low with minimum and intermediate levels of feed moisture and fiber content (0–5%). Luminosity values were an indicative that do not exist degradation in film materials due to condition extrusion process used.

  • Effect of the strain rate and drawing temperature on the mechanical behavior of EVOH and EVOH composites

     Franco Urquiza, Edgar; Gámez Pérez, José; Velázquez Infante, Julio César; Santana Pérez, Orlando Onofre; Martinez Benasat, Antonio; Maspoch Ruldua, Maria Lluïsa
    Advances in polymer technology
    Date of publication: 2012-02-27
    Journal article

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    The effect of the strain rate and draw temperature on the mechanical behavior of ethylene vinyl alcohol (EVOH) and EVOH composites was analyzed. When EVOH is stretched at moderate strain rates, evidence of strain-induced crystallization and recrystallization was observed. Higher strain rates produced less structural variation because the homogeneous flow of the chains and the crystalline perfection are restricted due to the rapid drawing. In reference to the drawing temperature, EVOH showed a diffusive yielding, and the mechanical parameters were reduced due to the softening of the crystalline region. For EVOH composites, the filler hinders the molecular mobility, causing an increase in the strength and restricting the plastic flow. However, the higher temperature, higher molecular mobility, and ductility are not so affected by the filler content

    The effect of the strain rate and draw temperature on the mechanical behavior of ethylene vinyl alcohol (EVOH) and EVOH composites was analyzed. When EVOH is stretched at moderate strain rates, evidence of strain-induced crystallization and recrystallization was observed. Higher strain rates produced less structural variation because the homogeneous flow of the chains and the crystalline perfection are restricted due to the rapid drawing. In reference to the drawing temperature, EVOH showed a diffusive yielding, and the mechanical parameters were reduced due to the softening of the crystalline region. For EVOH composites, the filler hinders the molecular mobility, causing an increase in the strength and restricting the plastic flow. However, the higher temperature, higher molecular mobility, and ductility are not so affected by the filler content.

  • Flexed-plate low energy impact of an epoxy-carbon laminate

     Martinez Benasat, Antonio; Xiang, Gao; Arencón Osuna, David
    Polymers and polymer composites
    Date of publication: 2012-07-01
    Journal article

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  • Low energy impact indentation of a modified polyethylene terephthalate by instrumented falling weight

     Martinez Benasat, Antonio; Arencón Osuna, David; Navas, Javier; Velasco Perero, Jose Ignacio
    Journal of applied polymer science
    Date of publication: 2012-04-27
    Journal article

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  • Study of the fracture behaviour of flexible polypropylene foams using the Essential Work of Fracture (EWF)

     Arencón Osuna, David; de Sousa Pais Antunes, Marcelo; Martinez Benasat, Antonio; Velasco Perero, Jose Ignacio
    Polymer testing
    Date of publication: 2012-04-01
    Journal article

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  • Estudio de mezclas de poliestireno y microesferas de vidrio: Comportamiento a impacto y predicción de inicio de fallo

     Sanchez Soto, Miguel Angel; Martinez Benasat, Antonio; Lladó, D; Briz, A; López-Vera, D
    Encuentro del Grupo Español de Fractura
    Presentation of work at congresses

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  • Indentación por impacto de baja energía

     Jiménez, O; Sanchez Soto, Miguel Angel; Gámez, R; Martinez Benasat, Antonio
    Encuentro del Grupo Español de Fractura
    Presentation of work at congresses

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  • High strain rate behaviour of polypropylene microfoams

     Gómez del Río, Teresa; Garrido, Miguel Ángel; Rodríguez Pérez, Jesús; Arencón Osuna, David; Martinez Benasat, Antonio
    International Conference on the Mechanical and Physical Behaviour of Materials under Dynamic Loading
    Presentation's date: 2012-09-05
    Presentation of work at congresses

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  • Influence of the injection moulding parameters on the cellular structure and thermo mechanical properties of ethylene-propylene block copolymer and PETG foams

     Arencón Osuna, David; Sanchez Soto, Miguel Angel; Martinez Benasat, Antonio; Gómez Gómez, Jaime Francisco; Rodríguez Pérez, Jesús; Salazar López, Alicia
    International Conference on Foam Materials & Technology
    Presentation's date: 2012-09-13
    Presentation of work at congresses

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    Microcellular injection moulding technology is capable of producing lightweight polymeric products. Microcellular foams are characterised by cell densities in the order of 109-1015 cells per cm3 and cell sizes between 10-100 μm in diameter. The foam morphology is determined by the injection moulding parameters, and it has been observed that depending on the parameters variations, cell structure may exhibit substantial morphological differences through the entire section, along the melt flow direction of the injected part. Using a constant temperature profile and blowing agent dosage rate, variations of 3 key injection moulding parameters (mould temperature, injection speed and shot volume) were studied to analyse the effect on foam morphology and thermal mechanical properties of single ethylene-propylene block copolymer (EPBC) and poly(ethylene glycol-co-cyclohexane- 1,4- dimethanol therephthalate) (PETG) specimens.

  • Comportamiento a fractura de láminas de espuma de polipropileno producidas mediante dos métodos diferentes de espumación

     Arencón Osuna, David; de Sousa Pais Antunes, Marcelo; Martinez Benasat, Antonio; Velasco Perero, Jose Ignacio
    Encuentro del Grupo Español de Fractura
    Presentation's date: 2012-03-22
    Presentation of work at congresses

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  • Efecto de la agudización de la entalla en la tenacidad de fractura medida en condiciones cuasiestáticas del policarbonato

     Salazar López, Alicia; Rodríguez Pérez, Jesús; Martinez Benasat, Antonio
    Encuentro del Grupo Español de Fractura
    Presentation's date: 2012-03-22
    Presentation of work at congresses

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  • Impact behaviour of carbon fibre reinforced epoxy and non-isothermal cyclic butylene terephthalate composites manufactured by vacuum infusion

     Agirregomezkorta, A.; Martinez Benasat, Antonio; Sanchez Soto, Miguel Angel; Aretxaga, G.; Sarrionandia, Mariasun; Aurrekoetxea Narbarte, Jon
    Composites Part B: Engineering
    Date of publication: 2011-07
    Journal article

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    Carbon fibre reinforced cyclic butylene terephthalate (CF-pCBT) composites non-isothermally processed by vacuum infusion starting from a one-component system have been successfully manufactured. Both the micro-structure and low-energy impact properties of the CF-pCBT have been investigated and compared with an epoxy system (CF-epoxy). The CF-pCBT composite presents higher solidification shrinkage than the CF-epoxy one, and its void content doubles that of the CF-epoxy. The CF-epoxy composite’s critical delamination threshold energy is slightly higher than that of the CF-pCBT, whereas the CF-pCBT composite absorbs twice as much energy before being penetrated. The lower interlaminar shear strength of the CF-pCBT composite is suggested to be the origin of its higher energy absorbing capability and less brittle behaviour.

  • Influence of nanoclay concentration on the CO2 diffusion and physical properties of PMMA montmorillonite microcellular foams

     de Redondo Realinho, Vera Cristina; de Sousa Pais Antunes, Marcelo; Martinez Benasat, Antonio; Velasco Perero, Jose Ignacio
    Industrial & engineering chemistry research
    Date of publication: 2011-11-08
    Journal article

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  • Microcellular Foaming of Layered Double Hydroxide-Polymer Nanocomposites

     Martinez Benasat, Antonio; de Redondo Realinho, Vera Cristina; de Sousa Pais Antunes, Marcelo; Maspoch Ruldua, Maria Lluïsa; Velasco Perero, Jose Ignacio
    Industrial & engineering chemistry research
    Date of publication: 2011
    Journal article

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    Microcellular foams of polystyrene (PS), poly(styrene-co-acrylonitrile) (SAN), and poly(methyl methacrylate) (PMMA) having organically modified layered double hydroxides (LDH) were prepared using a high-pressure CO2 dissolution foaming process and characterized both structurally and thermo-mechanically. The saturation concentration of CO2 was found to increase with the incorporation of LDH nanoparticles into the PMMA, while the opposite effect was observed in the PS and SAN nanocomposites with respect to the pure polymers. The CO2 desorption diffusion coefficient substantially decreased in the nanocomposites comparatively to the respective pure polymers. The incorporation of hydrotalcite (HT) into the polymers and subsequent foaming resulted in foams with finer and more isotropic cellular structures, related to a cell nucleation effect promoted by the particles. No significant differences were found among the several foamed nanocomposites. Both PS and SAN nanocomposite foams displayed higher glass transition temperatures than the respective unfilled ones, related to a higher amount of residual CO2 in the last, favoring plasticization. The contrary effect was observed inPMMA, attributed to a combined plasticizing effect promoted by the higher affinity of PMMA for CO2 and greater interaction with the organically modified HT platelets. Although no significant differences were found among the several nanocomposite foams and respective unfilled counterparts, the incorporation of HT limited the reduction observed in the specific storage moduli with foaming, related to a finer cellular structure induced by the HT particles.

  • Low energy impact indentation of an epoxy-carbon fiber laminate

     Martinez Benasat, Antonio; Xiang, Gao; Arencón Osuna, David; Velasco Perero, Jose Ignacio
    Polymers and polymer composites
    Date of publication: 2011-08-01
    Journal article

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  • Fracture behaviour of flexible polyethylene foams for potential use in damping applications

     Velasco Perero, Jose Ignacio; de Sousa Pais Antunes, Marcelo; Arencón Osuna, David; Martinez Benasat, Antonio
    Applied mechanics and materials
    Date of publication: 2011-09
    Journal article

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    The application of the essential work of fracture (EWF) methodology for the fracture behavior characterization of closed-cell low density polyethylene flexible foams is discussed in the present paper. The thickness of the foamed sheet and the relative orientation of the initial crack were the main parameters studied. The interpretation of the results is carried out on the basis of the material microstructure and the applicability of the testing method.

  • Simultaneous EWF, JIC and CTOD assessed on ductile polymer films

     Martinez Benasat, Antonio; Gámez Pérez, José; Delgado, A; Maspoch Ruldua, Maria Lluïsa
    International Conference on Fracture of Polymers, Composites and Adhesives
    Presentation's date: 2011-09-13
    Presentation of work at congresses

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    Determinación de KIC en compuestos de fibra corta a 1 m/s  Open access

     Martinez Benasat, Antonio; Arencón Osuna, David; Franco Urquiza, Edgar Adrian; de Sousa Pais Antunes, Marcelo; de Redondo Realinho, Vera Cristina
    Congreso Nacional de Materiales Compuestos
    Presentation's date: 2011-07-07
    Presentation of work at congresses

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  • CO2 desorption behaviour in poly(methyl methacrylate)-organoclay nanocomposites during supercritical CO2 dissolution microcellular foaming

     de Redondo Realinho, Vera Cristina; de Sousa Pais Antunes, Marcelo; Martinez Benasat, Antonio; Velasco Perero, Jose Ignacio
    International Conference on Diffusion in Solids and Liquids
    Presentation's date: 2011-06-29
    Presentation of work at congresses

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  • Compuestos de PLA/o-MMT: caracterización morfológica y mecánica

     Velázquez-Infante, Julio; Franco Urquiza, Edgar Adrian; Santana Pérez, Orlando Onofre; Martinez Benasat, Antonio; Maspoch Ruldua, Maria Lluïsa; Gamez Pérez, Jose; Carrasco, F
    Congreso Nacional de Materiales Compuestos
    Presentation's date: 2011-07-06
    Presentation of work at congresses

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    Fractura postcedencia de polímeros  Open access

     Maspoch Ruldua, Maria Lluïsa; Franco Urquiza, Edgar Adrián; Santana Pérez, Orlando Onofre; Gamez Pérez, Jose; Sanchez Soto, Miguel Angel; Velasco Perero, Jose Ignacio; Martinez Benasat, Antonio
    Encuentro del Grupo Español de Fractura
    Presentation's date: 2011-04-08
    Presentation of work at congresses

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  • The role of notch sharpening on the J-testing of thermoplastic polymers

     Salazar López, Alicia; Martinez Benasat, Antonio; Rodríguez Pérez, Jesús
    International Conference on Fracture of Polymers, Composites and Adhesives
    Presentation's date: 2011-09-12
    Presentation of work at congresses

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  • Preparación y caracterización termo-mecánica de espumas de polipropileno reciclado reforzado con fibras celulósicas

     de Sousa Pais Antunes, Marcelo; Ardanuy Raso, Monica; Martinez Benasat, Antonio; Velasco Perero, Jose Ignacio
    Congreso Nacional de Materiales Compuestos
    Presentation's date: 2011-07-06
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    Determinación de la tenacidad de fractura umbral de polipropilenos en la región de transición dúctil-frágil  Open access

     Salazar López, Alicia; Rodríguez Pérez, Jesús; Martinez Benasat, Antonio; Frontini, Patricia
    Encuentro del Grupo Español de Fractura
    Presentation's date: 2011-04-07
    Presentation of work at congresses

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  • Relevance of the femtolaser notch sharpening on the impact fracture of polycarbonate

     Arencón Osuna, David; Martinez Benasat, Antonio; Moreno, Pablo; Garcia Serrano, Ana
    EUROTEC
    Presentation's date: 2011-11-14
    Presentation of work at congresses

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  • Heat Transfer of Mineral-Filled Polypropylene Foams

     de Sousa Pais Antunes, Marcelo; de Redondo Realinho, Vera Cristina; Martinez Benasat, Antonio; Solórzano Quijano, Eusebio; Rodríguez Pérez, Miguel Ángel; Velasco Perero, Jose Ignacio
    Defect and diffusion forum
    Date of publication: 2010
    Journal article

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    The thermal conductivity of unfilled polypropylene foams produced using different foaming processes has previously been demonstrated to be mainly affected by the foam’s bulk density [1]. The influence of adding inorganic particles is now studied, with the thermal conductivity of the mineral-filled PP foams being determined using the Transient Plane Source Method (TPS). To this end, two different fillers were used. The incorporation of high amounts (50 and 70 wt.%) of magnesium hydroxide resulted in considerably higher thermally conductive foamed materials, with interesting thermal anisotropies being observed for the higher expansion ratio foams. On the contrary, adding montmorillonite (MMT) nanoparticles did not considerably alter the thermal conductivity of the foams, their value being mainly affected by the relative density.

  • Fracture behaviour of thermosetting polymers for ophtalmic lenses

     Martinez Benasat, Antonio; Artús, Pau; Dürsteter, Juan Carlos; Arencón Osuna, David
    Engineering failure analysis
    Date of publication: 2010-01-01
    Journal article

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  • Influence of the notch sharpening on the fracture toughness of bulk ethylene-propylene block copolymers

     Salazar López, Alicia; Rodríguez Pérez, Jesús; Segovia, Angelica; Martinez Benasat, Antonio
    Polymer testing
    Date of publication: 2010-03-02
    Journal article

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    The effect of the notch sharpening procedure on the fracture toughness computed under linear-elastic and elastic-plastic conditions (at low and high loading rates, respectively) of a bulk ethylene–propylene block copolymer has been investigated. The specimens utilized for fracture characterization were sharpened using a steel razor blade and the femtosecond laser ablation technique. The crack growth initiation parameter, JIC, determined with the help of the elastic-plastic fracture approach, and the fracture toughness, KIC, obtained with specimens verifying linear-elastic fracture mechanics assumptions, of the steel razor blade sharpened samples were higher than that of the femtolaser sharpened specimens. The plastic deformation occurring ahead of the crack tip during the sharpening method seems to be the reason for the dissimilarity of the fracture values. Moreover, the strain hardening suffered by the material close to the notch tip reduces the stable crack growth resistance evaluated under elastic-plastic conditions.

  • Relevance of the femtolaser notch sharpening to the fracture of ethylene-propylene copolymers

     Salazar López, Alicia; Rodríguez Pérez, Jesús; Segovia, Angelica; Martinez Benasat, Antonio
    European polymer journal
    Date of publication: 2010-02-17
    Journal article

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    The effect of the notch sharpening on the fracture toughness measured under Linear Elastic Fracture Mechanics (LEFM), Elastic–Plastic Fracture Mechanics (EPFM) and Post-Yielding Fracture Mechanics (PYFM) approaches has been evaluated. Bulk and film specimens of an ethylene–propylene block copolymer have been analyzed. The samples for fracture characterization were sharpened using a steel razor blade and the femtosecond laser ablation technique. Both notching techniques give rise to crack tip radii of the very same size. The fracture toughness of the specimens sharpened via femtolaser were 10%, 75% and 90% lower than that of the specimens sharpened via razor blade when determined with the help of LEFM, the EPFM approach as the multiple specimen method, and by the Essential Work of Fracture, respectively. Both in the bulk samples as in the films, the presence of plastic deformation, either large or small, occurring ahead of the crack tip during the sharpening seems to be the reason for the difference in the fracture values.

  • Aplicación de la mecánica de la fractura post-cedencia a polímeros

     Maspoch Ruldua, Maria Lluïsa; Franco Urquiza, Edgar Adrian; Gamez Pérez, Jose; Sanchez Soto, Miguel Angel; Velasco Perero, Jose Ignacio; Santana Pérez, Orlando Onofre; Martinez Benasat, Antonio
    Revista latinoamericana de metalurgia y materiales
    Date of publication: 2010-07-30
    Journal article

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    La técnica del trabajo esencial de fractura (EWF) se ha utilizado en la caracterización a fractura de materiales que desarrollan una amplia ductilidad y donde ocurre una completa cedencia antes del inicio de la propagación de la grieta. De esta manera, la técnica EWF caracteriza la fractura post-cedencia determinando dos parámetros: el trabajo esencial específico de fractura (we), relacionado con la superficie donde ocurre el proceso real de fractura, y el trabajo no esencial específico de fractura (wp), relacionado con el trabajo plástico realizado en la zona exterior de la zona de fractura. La técnica EWF ha sido utilizada satisfactoriamente, especialmente en polímeros, permitiendo el estudio de la influencia de distintas variables sobre el comportamiento a fractura. Su elevada sensibilidad así como su fácil aplicabilidad le confieren amplias ventajas sobre otras técnicas tales como la integral J. En este trabajo se describen los fundamentos de la técnica EWF y se recopilan algunos ejemplos de su aplicación, presentando un breve resumen de las aportaciones más relevantes realizadas por nuestro grupo de investigación sobre la técnica del EWF.

  • Comportamiento a fractura de distintos grados de copolímeros de propileno-etileno

     SEGOVIA UREÑA, NORMA ANGÉLICA
    Defense's date: 2010-07-27
    Department of Materials Science and Metallurgy, Universitat Politècnica de Catalunya
    Theses

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  • Influence of processing on the ethylene-vinyl alcohol (EVOH) properties: Application of the successive self-nucleation and annealing (SSA) technique

     Franco Urquiza, Edgar Adrian; Santana Pérez, Orlando Onofre; Gamez Pérez, Jose; Martinez Benasat, Antonio; Maspoch Ruldua, Maria Lluïsa
    Express polymer letters
    Date of publication: 2010-03
    Journal article

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    Films of EVOH copolymers, processed three times by twin-screw extrusion were prepared using a cast-film line. The variation on the melt flow rate (MFR) and rheological behaviour of the films were determined, as well as the thermal properties assessed by differential scanning calorimetry (DSC) and dynamic-mechanical thermal analysis (DMTA). As the results showed that the reprocessing induced an increase in the viscosity and orientation of the films, it was suggested that structural modifications from chain-extension or cross-linking reactions promoted by hydroxyl and residual acetoxyl groups, could be occurring. The successive self-nucleation and annealing (SSA) technique was applied, evidencing the structural modifications on the EVOH copolymer.

  • The role of notching damage on the fracture parameters of ethylene propylene block copolymers

     Salazar López, Alicia; Segovia, Angelica; Martinez Benasat, Antonio; Rodríguez Pérez, Jesús
    Polymer testing
    Date of publication: 2010-03-26
    Journal article

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    The influence of the notching procedure on the fracture toughness measured via Elastic- Plastic Fracture Mechanics has been analyzed on four different ethylene-propylene block copolymers with two distinct dimensions, paying special attention to the morphology of the area surrounding the crack tip front. Two sharpening techniques were evaluated: the traditional steel razor blade and the femtolaser ablation process. The fracture toughness of the razor blade sharpened samples was always higher than that of the femtolaser sharpened specimens. Also, the fracture toughness of the razor blade samples was dependent on the thickness of the samples, whereas the fracture toughness of the femtolaser sharpened specimens was not influenced by the dimensions of the test specimens. The microscopic analysis of non-tested samples showed that the crack tip radii were similar for both type of sharpened samples but the damage and its extension ahead of the crack tip was dependent on the notching technique, the copolymer type and the dimensions of the analyzed specimen. The femtolaser sharpened samples presented a very tinyheat affected zone ahead of the crack tip, the size of which was independent of the copolymer type and the dimensions of the test specimen. On the other hand, the steel razor blade sharpened samples showed an area surrounding the crack tip formed by plastic deformation, the length of which increased for the smaller size of sample and for higher ethylene content in the copolymer.

  • Essential work of fracture analysis of the tearing of a ductile polymer film

     Martinez Benasat, Antonio; Segovia, Angelica; Gamez Pérez, Jose; Maspoch Ruldua, Maria Lluïsa
    Engineering fracture mechanics
    Date of publication: 2010-09
    Journal article

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    The fracture behaviour of a 0.5 mm thick ethylene-propylene block copolymer, previously evaluated using the essential work of fracture method, has been analyzed again in more detail, using different plots, allowing the determination of the crack initiation displacement and stress. In such plots is evidenced that the especific essential work of fracture, we, corresponds to the energy just up to crack initiation value that can be related with Јo. Also, it has been found a novel relationship between the plastic term ßwp and the crack initiation stress, σi.