Influence of the size and amount of cork particles on the toughness of a structural adhesive

The inclusion of particles (nano or micro) is a method to improve the mechanical properties such as toughness of structural adhesives. Structural adhesives are known for their high strength and stiffness but also for their low ductility and toughness. There are many processes described in the literature to increase the toughness, being one of the most common the use of rubber particles. In the present study, natural micro particles of cork are used with the objective to increase the toughness of a brittle epoxy adhesive. The idea is for the cork particles to act like as a crack stopper leading to more energy absorption. The influence of the cork particle size and amount were studied. Particles of cork ranging from 38 to 250 µm were mixed in the epoxy adhesive Araldite 2020 from Huntsman. The amount of cork in the adhesive was varied between 1 and 5% in weight. Surface treatment (low pressure plasma) was applied to the cork powder to assess the effect of the interaction adhesive-cork with several degrees of adhesion

Advanced g-mps-pmma bone cements: Influence of graphene silanisation on fatigue performance, thermal properties and biocompatibility

The incorporation of well-dispersed graphene (G) powder to polymethyl methacrylate(PMMA) bone cement has been demonstrated as a promising solution to improving its mechanicalperformance. However, two crucial aspects limit the effectiveness of G as a reinforcing agent: (1)the poor dispersion and (2) the lack of strong interfacial bonds between G and the matrix of thebone cement. This work reports a successful functionalisation route to promote the homogenousdispersion of G via silanisation using 3-methacryloxypropyltrimethoxy silane (MPS). Furthermore,the effects of the silanisation on the mechanical, thermal and biocompatibility properties of bonecements are presented. In comparison with unsilanised G, the incorporation of silanised G (G_MPS1and G_MPS2) increased the bending strength by 17%, bending modulus by 15% and deflection atfailure by 17%. The most impressive results were obtained for the mechanical properties underfatigue loading, where the incorporation of G_MPS doubled the Fatigue Performance Index (I) valueof unsilanised G-bone cement—meaning a 900% increase over the I value of the cement without G.Additionally, to ensure that the silanisation did not have a negative influence on other fundamentalproperties of bone cement, it was demonstrated that the thermal properties and biocompatibilitywere not negatively impacted—allowing its potential clinical progression

Biomechanical Test of a New Endoprosthesis for Cylindrical Medullary Canals in Dogs

Exo-endoprosthesis is a limb salvage procedure for animals, although only expensive metal devices have been described. Now-a-days, new materials for this type of implant could be considered due to novel and affordable manufacturing techniques. However, a factor of safety (FoS) should be considered. There are kinetic and kinematic studies of canine natural gaits, which can be used to establish an FoS for mechanical tests for new non-metallic devices. Polyetheretherketone (PEEK) is used in different specialties in human medicine. Its mechanical properties (and its close mechanical stiffness to that of bone) make this polymer an alternative to metals in veterinary traumatology. PEEK could also be used in 3D printing. The suitability of a novel inner part of an exo-endoprosthesis manufactured by fuse deposition modeling (FDM) was presented in this study for long canine bones. Mechanical characterization of 3D-printed PEEK material and ex vivo mechanical tests of a customized endoprosthesis were performed to address it. Young's modulus of 3D-printed PEEK suffered a reduction of 30% in relation to bulk PEEK. Customized 3D-printed PEEK endoprostheses had promising outcomes for the tibiae of 20 kg dogs. Pure compression tests of the non-inserted endoprostheses showed a maximum force of 936 +/- 199 N. In the bending tests of non-inserted endoprostheses, the PEEK part remained intact. Quasistatic mechanical tests of bone-inserted endoprostheses (compression-bending and pure compression tests) reached a maximum force of 785 +/- 101 N and 1,642 +/- 447 N, respectively. In fatigue tests, the samples reached 500,000 cycles without failure or detriment to their quasistatic results. These outcomes surpass the natural weight-bearing of dogs, even during a galloping pace. In conclusion, the 3D-printed PEEK part of the endoprosthesis for an exo-endoprosthesis can withstand loading, even during a galloping pace.Depto. de Medicina y Cirugía AnimalFac. de VeterinariaTRUEComunidad de Madridpu

Influencia de las características superficiales de un sustrato en la resistencia de una unión adhesiva

Uno de los objetivos que se plantean cuando se realiza una unión adhesiva es que su resistencia sea lo más elevada posible para los esfuerzos a los que va a estar solicitada. Además de las propias características del adhesivo empleado, está la resistencia que se genera en la interfase. En trabajos anteriores se ha caracterizado la topografía de la superficie del sustrato. En este trabajo se han realizado ensayos de resistencia de la unión adhesiva sometida a ensayos de tracción pura, buscando la relación con las características de las superficies tratadas con diferentes tratamientos mecánicos y químicos. Se ha comprobado que el valor de la rugosidad influye en la resistencia, pero condicionado por el tratamiento aplicado

los medios electrónicos en la modalidad contractual de licitación pública: una comparación entre el derecho colombiano y chileno

Los procesos de contratación entre el Estado y los particulares han sido revestidos a lo largo de la historia de múltiples formalismos que se han traducido en reducida participación del sector privado en la contratación, así como en incentivos para las prácticas corruptas. La Licitación Pública, pese a ser la norma por excelencia para seleccionar los oferentes mediante una evaluación objetiva no es la comúnmente aplicada, y parte de esa problemática es debida al mal uso de las Tecnologías de la Información y Comunicación a los procesos.En este documento se analiza cómo ha sido la evolución histórica de los procesos de licitación pública en Colombia y Chile y la participación de los medios electrónicos como mecanismos que permiten una mayor transparencia, así como las limitaciones actuales que no han sido subsanadas pese a un cambio de normatividad constante.Se resaltan además algunos aspectos relevantes que contiene la legislación colombiana asimilados al sistema electrónico chileno www.chilecompra.cl, que desde hace diez años inició con una plataforma de contratación por vía digital, con fuerte influencia del mercado globalizado y aperturista de la nación del cono sur, con características relativamente aplicables a la Colombia del siglo XXI

Mechanical properties and fire-resistance of composites with marble particles

The main aim of this work is to manufacture a composite material based on a natural material (marble) with acceptable mechanical properties and fire resistance, for being used in habitat industry as floor or wall in buildings. Marble used as raw material is the waste powder of quarry or plate manufacturing. To achieve this objective, polyester matrix composites with 50 wt.% of marble and 3 wt.% of glass fiber (short fiber or mesh) were prepared. The novelty of this study is the high percentage of ceramic material added to a polymer matrix composite and the fire resistance study. Samples were characterized mechanically through flexural test, Charpy impact test, compression test and wear resistance by pin-on-disk test. Fracture surfaces were analyzed by scanning electron microscope (SEM), and wear tracks were studied by SEM and 3D optical profilometer. Besides, samples were subjected to fire test using a Bunsen burner at 900 °C for 20 min. Sample temperature at the opposite-to-fire test side was measured with an infrared thermometer. Results show that marble improves mechanical properties of polyester and the effect of the glass fiber depends on its morphology (fiber or mesh). Fire resistance is high, and the fire goes out when the flame is turned off. Furthermore, the mesh maintains the integrity of the sample.This research received funding from the SUDOE project SOE1/P1/E307

Evaluation of seminal characteristics of Pelibuey and East Friesian rams at two different times of the year

Objective: To determine the changes in seminal quality of Pelibuey and East Friesian rams during the non-breeding (long days; March-June) and breeding seasons (short days; September-December) at 19° north latitude. Design/methodology/approach: To determine changes in seminal quality over time, seminal parameters of rams, collected with an artificial vagina were evaluated over 32 weeks. An analysis of variance was performed with a completely randomized design in a 2 x 2 factorial arrangement (breed and season). Results: No differences were found within breeds or between breeds in the same season in the evaluated seminal parameters; however, differences were reported between seasons in the live weight parameters, lower in the non-reproductive season, in addition to an increased scrotal circumference and mass motility during the reproductive season. Study limitations/implications: Semen parameters estimation, in field trials, is subjective compared to computerized semen evaluation systems, it is therefore desirable to have extensive experience in semen evaluation at the field level before starting the study. To confirm the results obtained in this study, a new experiment with a larger number of experimental units is suggested. Findings/conclusions: It is concluded that in the environmental and management conditions, where the seminal evaluation took place, no differences were found between breeds, suggesting that the Pelibuey and East Friesian breeds at 19° north latitude do not decrease their seminal parameters during the non-breeding season compared to the breeding season. This suggest that these two sheep breeds are able to reproduce, in such conditions, all year round

Influence of acrylic adhesive viscosity and surface roughness on the properties of adhesive joint

In adhesion, the wetting process depends on three fundamental factors: the surface topography of the adherend, the viscosity of the adhesive, and the surface energy of both. The aim of this paper is to study the influence of viscosity and surface roughness on the wetting and their effect on the bond strength. For this purpose, an acrylic adhesive with different viscosities was synthesized and some properties, such as viscosity and surface tension, were studied before adhesive curing took place. Furthermore, the contact angle and the lap-shear strength were analyzed using aluminum adherends with two different roughnesses. Scanning electron microscopy was used to determine the effect of the viscosity and the roughness on the joint interface. The results showed that the adhesive exhibits an optimal value of viscosity. Below this value, at low viscosities, the low neoprene content produces poor bond strength due to the reduced toughness of the adhesive. Additionally, it also produces a high shrinkage during curing, which leads to the apparition of residual stresses that weakens the interfacial strength. However, once the optimum value, an increase in the viscosity produces a negative effect on the joint strength as a result of an important decrease in the wettability

Diagnóstico global de fallas en vigas de aluminio usando niveles de presión sonora

El uso de medios acústicos para diagnosticar fallas data de la antigüedad, dado que con un golpe en la estructura se podía detectar por su sonido si la pieza era defectuosa. En un trabajo previo hemos mostrado como es posible realizar diagnostico global no destructivo de fallas en vigas de aleación de aluminio EN AW 7075 clasificando con una red neuronal las Funciones de Respuesta en Frecuencia obtenidas con de un ensayo de vibración. En ese trabajo las fallas están simuladas mediante la unión de dos vigas de aluminio que están pegadas con epoxi, donde la superficie que se solapa está totalmente adherida para simular la viga en perfectas condiciones o está solo parcialmente adherida con un 25%, 50% o un 75% para simular diferente tamaño de daño. Los resultados fueron altamente positivos con una red neuronal backpropagation que clasifica según el tamaño de daño. El problema es que la metodología de Funciones de Respuesta en Frecuencia requiere para sus mediciones sensores que tienen un aporte significativo en el peso de la estructura a ensayar. Las mediciones se realizaron a través del uso de un soporte universal de cuerdas y un sensor de presión de tipo micrófono para medir los niveles de presión sonora y clasificar las vigas según el tamaño del daño usando una red neuronal cuya entrada serán valores de niveles de presión sonora para un rango de frecuencias determinado. Con esta metodología se elimina la influencia del aporte del peso del sensor en la estructura y de esa forma se evita modificar la dinámica de la estructura a medir para diagnosticar posibles fallas.Fil: Zapico, Adriana Maria. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Computación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Molisani Yolitti, Leonardo. Universidad Nacional de Rio Cuarto. Facultad de Ingeniería. Departamento de Mecanica. Grupo de Acustica y Vibraciones; ArgentinaFil: O'brien, Ronald Julián. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Rio Cuarto. Facultad de Ingeniería. Departamento de Mecanica. Grupo de Acustica y Vibraciones; ArgentinaFil: Del Real Romero, Juan Carlos. Universidad Pontificia Comillas de Madrid; EspañaFil: Ballesteros, Yamila. Universidad Pontificia Comillas de Madrid; EspañaFil: Ponso, Nicolás. Universidad Nacional de Rio Cuarto. Facultad de Ingeniería. Departamento de Mecanica. Grupo de Acustica y Vibraciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Dispositivo reductor de velocidad aplicable a vías de circulación

Dispositivo reductor de velocidad aplicable a vías de circulación; que comprende un cuerpo destinado a conformar un resalto en una vía de circulación con, al menos, un módulo (la) provisto de: - una estructura fija de soporte destinada a anclarse al pavimento; - una caja móvil; - un generador piezoeléctrico, montado en el interior de la caja móvil y - un circuito eléctrico; comprendiendo el generador piezoeléctrico una serie de piezoeléctricos dispuestos en voladizo sobre un perfil y conectados entre sí; provocando los movimientos de descenso y de ascenso de la caja móvil la flexión de los piezoeléctricos y la generación de una diferencia de potencial por parte de dichos piezoeléctricos.Solicitud: 201730572 (31.03.2017)Nº Pub. de Solicitud: ES2613752A1 (25.05.2017