Fibre–Wood Laminate Biocomposites: Seawater Immersion Effects on Flexural and Low Energy Impact Properties

The present paper explores a new concept of a hybrid eco-composite by substituting the natural fibre plies with thin wood veneers. The new composite, named Fibre–Wood Laminate (FWL), is inspired by fibre–metal laminate materials. The studied FWL configuration consisted of a single thin pinewood veneer at each of the outer layers of a flax woven fabric reinforced bio-epoxy composite manufactured by infusion. Three-point bending results showed that wood veneer gives a highly anisotropic nature to the FWL. In the best case, with the grain of the wood at 0°, the stiffness and the strength increased by 28 and 41%, respectively, but reduced the strain-at-break by 27% compared to the flax fibre reinforced bio-epoxy (FFRB). The penetration and perforation energy thresholds and the peak force of the FWL obtained by falling weight impact tests were 32, 29, and 31% lower than those of the FFRB, respectively. This weakening was due to using single wood veneers, so the challenge for improving impact properties will be to explore thicker FWLs with different stacking sequences and orientations. The effect of immersing the FWL in seawater also showed considerable differences. The epoxy matrix filled the cellular structure of the wood veneers, creating a barrier effect and reducing the amount of water absorbed by the flax fibres.The research in this paper was supported by the Vice-Ministry of Universities and Research of the Basque Government (Grants No. IT1613-22 and IT1514-22)

Aprovechamiento de aguas residuales y residuos del pacifico colombiano para la generación eléctrica

The Colombian Pacific region has 36 municipalities corresponding to areas not interconnected to the National Interconnected System [1], and a population of 1,332,082 inhabitants [2]. The region's electricity supply is made partially from diesel plants with coverage of 6 to 8 hours a day, [3]. Currently, neither solid waste nor wastewater generated has adequate disposal, which generates great environmental and health impacts. The present study estimated the energy potentials that can be obtained from these wastes produced in the region. The calculated theoretical energy potential was 30 MWh / year and the technical energy potential was 20,589 kWh / year, considering an energy conversion efficiency of 50 % and an effective collection of 70%. These potentials cover 5.2% of the total energy demand in the region for 24 hours a day. To solve a total coverage, we can think about the implementation of hybrid systems of distributed generation using the current diesel plants with the supplement of clean energy sources (other biomass residues, water resources or photovoltaic solar systems).La región pacifica colombiana cuenta con 36 municipios correspondientes a zonas no interconectadas al Sistema Interconectado Nacional [1], y una población de 1.332.082 habitantes [2]. El suministro eléctrico de la región se hace de manera parcial a partir de plantas diésel con cubrimiento de 6 a 8 horas diarias, [3] Actualmente, ni los residuos sólidos ni las aguas residuales generadas tienen disposición adecuada, lo que genera impactos ambientales y de salubridad; el presente estudio estimó los potenciales energéticos que pueden obtenerse a partir de estos residuos producidos en la región. El potencial energético teórico calculado fue de 30 MWh/año y el potencial energético técnico, fue de 20.589 kWh/año, al considera una eficiencia de conversión energética de 50% y una recolección efectiva del 70%. Estos potenciales permiten cubrir el 5,2% de la demanda energética total de la región durante 24 horas al día. Para garantizar un cubrimiento total, se pueden pensar en la implementación de sistemas híbridos de generación distribuida usando las plantas diésel actuales con el suplemento de fuentes de energía limpias (otros residuos de biomasa, recursos hídricos o sistemas solares fotovoltaicos)

Design and manufacture of a self-supporting racing motorcycle seat made on carbon fiber

Este trabajo presenta el diseño, cálculo y fabricación del colín de moto de competición, que ha participado en la edición MotoStudent 2016, celebrada en octubre de 2016 en el circuito de Alcañiz, representando a la Universidad de Málaga. En esta ocasión se presentaban dos motos, una dentro de la categoría Petrol (motor de 4 tiempos y 250 cc) y otra en la categoría Electric. Se trata de una estructura autoportante que sustituye a la utilización del subchasis y colín tradicionales, con el objetivo de que la solución sea más ligera que el conjunto anterior. Como material se ha seleccionado un tejido de carbono sarga 2x2 de 3K y 200 g/m2 y resina epoxi Resoltech 1070/1074. El proceso de fabricación seleccionado ha sido el moldeo manual y posterior compactado con bolsa de vacío. Mediante la utilización de modelos micromecánicos y a partir del porcentaje de fibra, se han estimado las propiedades de la lámina elemental de material compuesto. Dichas propiedades han sido implementadas en el programa de elementos finitos Patran-Nastran para la optimización de la pieza. Una vez diseñado el colín, se ha fabricado un modelo de la pieza a partir del mecanizado de placas de madera MDF que ha servido para fabricar el molde de la pieza en fibra de vidrio. Los colines diseñados fueron homologados por la organización de la competición. El colin desarrollado es un 50% más ligero que la solución actual. El molde fabricado permite la obtención de varias piezas con la consiguiente reducción de costes.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Evaluation of impact severity reduction in a bi-material demonstrator based on recycled tires.

Actualmente, el elevado uso al que se ven sometidos los vehículos, unido a su importante volumen como producto de consumo, supone un gran problema medioambiental, ya que anualmente, entre otras cosas, se generan millones de toneladas de residuos provenientes de los neumáticos que cumplen su vida útil, también llamados neumáticos fuera de uso, NFU en adelante. Una de las formas de mitigar este problema es darle un nuevo uso a este material. En este contexto, se creó la presente línea de investigación, enfocada a evaluar el efecto que la adición de un aglomerado, formado por pellets procedentes de NFU y poliuretano, a los actuales sistemas de protección vial, pueden tener sobre la severidad del impacto contra ellos. Se muestran resultados preliminares, a escala de laboratorio, comparando resultados experimentales sobre un elemento metálico, construido ad hoc, con los resultados obtenidos sobre el mismo elemento al que se ha añadido el aglomerado. Considerando que las conclusiones definitivas de esta línea de investigación habrían de obtenerse de ensayos a escala real, que no son económicamente viables, se desarrolla, en este trabajo, un modelo numérico, cuya fiabilidad se evalúa en base a su comparación con los resultados experimentales. Un modelo numérico fiable aportaría una potente herramienta de diseño de sistemas de protección vial bimaterial, incluyendo el aglomerado, así como para reducir el número de ensayos, a escala real. En consecuencia, los objetivos de este trabajo son la comprobación de la disminución de la severidad del impacto por la presencia del material reciclado, así como el desarrollo de un modelo numérico que permita valorar esta disminución sin acudir a ensayos reales.In the contemporary context, the substantial accumulation of non-biodegradable end-of-life tire residues poses a significant environmental concern. Annually, thousands of tons of these residues, highly flammable and constituting a severe fire hazard, are generated. This study proposes a novel application for these residues: incorporation into guardrails to create a hybrid-material system capable of dissipating higher levels of impact energy. This innovation aims to enhance the safety of guardrails. To achieve this objective, a numerical model will be employed to quantify the impact mitigation achieved through the introduction of a viscoelastic material derived from end-of-life tires. A downscaled model is used to establish a robust numerical-experimental correlation. Once satisfactory results are obtained from the numerical model, the virtual analysis of a full-scale model will be possible, without the need for physical tests, which are very expensive.Consejería de Transformación Económica, Industria, Conocimiento y Universidades, dentro de los Proyectos I+D+i en el marco del Programa Operativo FEDER, a través del proyecto “Absorción de Energía de Impacto a Partir de Neumáticos Fuera de Uso -NFU- Reciclados. Aplicación a Sistemas de Contención de Vehículos” de referencia UMA20-FEDERJA-028 Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Piezoresistive laminates for structural monitoring. Laboratory application.

El ciclo de vida de una estructura se ve comúnmente limitada bien sea por su degradación, bien por los cambios de uso a los se ven sometidas, siendo necesario reforzarlas si se desea alargar su vida útil. Entre las técnicas de refuerzo comúnmente empleadas destaca el uso de laminados de polímeros reforzados. Por otro lado, durante los últimos veinticinco años se han desarrollado técnicas de monitorizado que permiten conocer la salud estructural en tiempo real. La aparición de resinas funcionalizadas con nanocompuestos de carbono que muestran un comportamiento piezorresistivo podría ser un camino para conseguir ese doble objetivo, sensorizar y reforzar una estructura. En el presente trabajo se presenta la aplicación de (i) una resina piezorresistiva como película sensible y (ii) los laminados sensitivos desarrollados, a la monitorización y/o refuerzo de un demostrador de laboratorio.The need to reinforce existing structures (degraded structures, modifications in the working conditions of the structure, etc.) is quite common. One of the most commonly used types of reinforcement is laminated composite reinforcement. In previous works, the authors have analyzed the piezoresistive response of nanocomposites based on carbon nanotubes and nanofibers and glass fiber laminates made with nanocomposites. The results have shown their piezoresistive capability. In this work, the ability of these laminates to provide information on the structural state of laboratory demonstrators has been tested. For this purpose, sensitive laminates have been fabricated and bonded to commercial pultrusion beams and subjected to (i) cyclic loading in undamaged and damaged situations and (ii) increased loading until structural failure. The results show that the functionalized resin has a sensitive capability and that the laminates have both sensitive and reinforcing capabilities. Therefore, both solutions are valid for monitoring structural health.Ministerio de Economía y Competitividad y Fondo Europeo de Desarrollo Regional, bajo el título Ciencia, Innovación y Universidades de España a través del proyecto “Monitorización de la salud estructural autoabastecida mediante refuerzos inteligentes de nanocompuestos (MSEAARINC)” de referencia RTI2018-094945-B-C21. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Determining static elastic modulus of weak sandstone in Andalusian historical constructions from non-destructive tests: San Cristóbal's stone

This work presents a relationship between static and dynamic elastic moduli for San Cristóbal’s stone, which was used to build some of the most representative historical constructions in Andalusia (Spain) during 15th-18th centuries, including religious, military and civil buildings. Numerical models are able to provide useful information in structural health assessment of historical constructions, but static elastic modulus is necessary to perform them. This is why it is particularly interesting to count on an equation to predict this parameter from others, such as dynamic elastic modulus, which can be obtained in situ and through tests based on wave propagation. A new relationship is proposed after having shown that equations previously defined by other authors are not valid for San Crist´obal’s stone. The prposed relationship in this work is based on a set of physical and mechanical experimental tests carried out in lab on 17 specimens directly extracted from support elements of Santiago’s (Jerez de la Frontera, Cádiz-Spain). Linear, polynomial and nonlinear multiple regressions were considered, as well as the inclusion of other parameters, such as bulk density and porosity. However, an equation with a coefficient of determination of 0.95 was achieved with a simple regression where only dynamic elastic modulus was involved. This simple equation allows to predict static modulus of San Cristóbal’s Stone with a high level of confidence and only from one parameter, that can be obtained in situ through non-destructive techniques and respectfully to built heritage. Finally, a first approximation to the application on an ancient construction is provided. Six columns of the Monastery of San Jerónimo de Buenavista, in Seville (Spain) underwent tests based on the propagation of wave to determine in situ their dynamic elastic modulus. The In situ results for the dynamic elastic modulus are consistent with those obtained in lab

Piezoelectric composite cements: Towards the development of self-powered and self-diagnostic materials

Piezoresistivity is the most commonly used sensing principle in cement-based smart composites for strainmonitoring applications. Nonetheless, the need for external electric power to conduct electrical resistivity measurements restricts the scalability of this technology, especially when implemented in remote structures. To address this issue, this manuscript thoroughly analyses the piezoelectric properties of cement composites doped with reduced graphene oxide (rGO) and evaluates their potential as self-powered strain sensors. To do so, a comprehensive methodology involving voltammetry measurements, open circuit potential determination, and uniaxial compression testing is developed to determine the piezoelectric coefficients of charge �33 and voltage �33. Furthermore, a novel circuital model for signal processing of the electromechanical response is developed and experimentally validated in terms of time series of output voltage, resistance, and the generated electric power. The developed methodology is applied to laboratory samples manufactured following two different filler dispersion methods. The presented results evidence that samples prepared by ultrasonic cleaner dispersion achieve optimal properties, with a piezoelectric charge coefficient of 1122.28 ± 246.67 pC/N, about 47 times greater than previously reported composites in the literature. Unlike piezoresistive cement-based composites, a remarkable nonlinear correlation between the fractional change in the intrinsic resistance of the material and the applied mechanical strain has been observed. Instead, a considerable linearity (R 2 = 0.96) between the externally applied mechanical strain and the generated (piezoelectric) electric power has been found, which suggests the great potential of the latter for conducting off-the-grid strain monitoring applications

Pathogenicity island cag, vacA and IS605 genotypes in Mexican strains of Helicobacter pylori associated with peptic ulcers

<p>Abstract</p> <p>Background</p> <p><it>Helicobacter pylori </it>is associated with chronic gastritis, peptic ulcers, and gastric cancer. Two major virulence factors of <it>H. pylori </it>have been described: the pathogenicity island <it>cag </it>(<it>cag </it>PAI) and the vacuolating cytotoxin gene (<it>vacA</it>). Virtually all strains have a copy of <it>vacA</it>, but its genotype varies. The <it>cag </it>PAI is a region of 32 genes in which the insertion of IS<it>605 </it>elements in its middle region has been associated with partial or total deletions of it that have generated strains with varying virulence. Accordingly, the aim of this work was to determine the <it>cag </it>PAI integrity<it>, vacA </it>genotype and IS<it>605 </it>status in groups of isolates from Mexican patients with non-peptic ulcers (NPU), non-bleeding peptic ulcers (NBPU), and bleeding peptic ulcers (BPU).</p> <p>Methods</p> <p>The <it>cag </it>PAI integrity was performed by detection of eleven targeted genes along this locus using dot blot hybridization and PCR assays. The <it>vacA </it>allelic, <it>cag </it>PAI genotype 1 and IS<it>605 </it>status were determined by PCR analysis.</p> <p>Results</p> <p>Groups of 16-17 isolates (n = 50) from two patients with NPU, NBPU, and BPU, respectively, were studied. 90% (45/50) of the isolates harbored a complete <it>cag </it>PAI. Three BPU isolates lacked the <it>cag </it>PAI, and two of the NBPU had an incomplete <it>cag </it>PAI: the first isolate was negative for three of its genes, including deletion of the <it>cagA </it>gene, whereas the second did not have the <it>cagM </it>gene. Most of the strains (76%) had the <it>vacA </it>s1b/m1 genotype; meanwhile the IS<it>605 </it>was not present within the <it>cag </it>PAI of any strain but was detected elsewhere in the genome of 8% (4/50).</p> <p>Conclusion</p> <p>The patients had highly virulent strains since the most of them possessed a complete <it>cag </it>PAI and had a <it>vacA </it>s1b/m1 genotype. All the isolates presented the <it>cag </it>PAI without any IS<it>605 </it>insertion (genotype 1). Combined <it>vacA </it>genotypes showed that 1 NPU, 2 NBPU, and 1 BPU patients (66.6%) had a mixed infection; coexistence of <it>H. pylori </it>strains with different <it>cag </it>PAI status was observed in 1 NBPU and 2 BPU (50%) of the patients, but only two of these patients (NBPU and BPU) had different <it>vacA </it>genotypes.</p

Identificación de las propiedades mecánicas de la piedra de San Cristóbal mediante técnicas no destructivas

La alteración de la Piedra arenisca es una inquietud para los técnicos y restauradores del patrimonio histórico, ya que es la piedra base de muchos edificios de nuestro patrimonio histórico. En este trabajo nos vamos a centrar en la piedra extraída en el Cerro de San Cristóbal, situada en el Puerto de Santa María (Cádiz). Una de las características de esta piedra es un material muy degradable, que unido a las alteraciones provocadas por el paso del tiempo y por los agentes atmosféricos están poniendo en peligro parcial o totalmente algunos de los edificios históricos más importantes de nuestra región. El objetivo de este trabajo consiste en contribuir a la caracterización mecánica de la piedra del Cerro de San Cristóbal, utilizando métodos físicos y geofísicos. Para desarrollar este trabajo contamos con una serie de probetas pertenecientes a la Iglesia de Santiago de Jerez de la Frontera, las cuales se han obtenido extrayendo varios testigos en el sentido paralelo al eje de las columnas. La caracterización de sus propiedades físicas se ha centrado en la determinación de su densidad, (seca, sumergida y saturada), porosidad abierta, absorción, volumen de poros, volumen aparente, mientras que sus propiedades mecánicas se ha determinado mediante ensayos dinámicos, determinando su módulo de deformación identificando sus frecuencias naturales de vibración. Dicha campaña dinámica se ha realizado a diferentes niveles de humedad seca 0%, y saturadas al 40%, 80% y el 100%. La identificación de sus propiedades mecánicas se ha realizado basándonos en la norma UNE 14146

Association of physical activity with muscular strength and fat free mass in adolescents; The HELENA Study

Objective: To analyze the association of objectively assessed physical activity (PA) with muscular strength and fat free mass in adolescents, and to determine whether meeting the current PA recommendations is associated with higher levels of muscular strength and fat free mass. Subjects/Methods: The present cross-sectional study comprised 363 Spanish adolescents (180 females) aged 12.5-17.5 years. PA was assessed by accelerometry and expressed as average PA (counts/min), and min/day of inactive, light, moderate, vigorous and moderate to vigorous PA (MVPA). MVPA was dichotomized into <60 min/day and ≥60. Upper body muscular strength was measured with the handgrip strength test, and lower body muscular strength was measured with the standing broad jump, squat jump, counter movement jump and Abalakov tests. Fat free mass was measured by DXA. Results: We observed positive associations between vigorous PA and all the lower body muscular strength tests except for the counter movement jump in males. PA was not associated with fat free mass in both males and females. Male adolescents engaged in at least 60 min/day MVPA performed better in the standing broad jump test. Conclusions: The findings of the present study suggest that only vigorous PA is associated with muscular strength, particularly lower-body muscular strength in male adolescents