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Abstract This work analyses the fatigue delamination and fracture stress behaviour under mode I of adhesive joints made on an epoxy matrix composite material with unidirectional carbon fibre reinforcement and a commercial epoxy-based adhesive. DCB type tests (for mode I) were used with the aim to quantify the influence of the period of exposure to a degradation process in a salt spray chamber, to which the tested samples were subjected, on their fatigue behaviour. For this purpose and after a previous static characterisation of the material in which the critical values of the energy release rate for different exposure periods were determined, the levels of the energy release rate to be applied in the fatigue tests and the exposure periods to be considered (no exposure, exposure during one week and twelve weeks) and a ratio of fatigue stress levels of R = Gmin/Gmax = 0.1 were defined. From this experimental data, the G-N fatigue initiation curves and the G-da/dN growth curves were obtained. The experimental data obtained, in the fatigue initiation phase of the delamination process, have been treated by means of a probabilistic model based on a Weibull distribution, the application of models of these characteristics has allowed a better interpretation of the experimental results obtained. The most relevant result of the work is that, in general, the fatigue limits obtained for the adhesive joint, under mode I fracture, when subjected to a degradation process in a saline environment, do not translate into a relevant loss of its resistance capacity against this fatigue delamination phenomenon, in its initiation phase. On the other hand, the crack growth rates of the material subjected to different periods of exposure to a saline environment are similar and higher than those obtained for the material without exposure.

The fatigue delamination process of three different aeronautical quality composites subject to mode III fracture loading is studied experimentally in this paper with the aim of analysing the effect of the type of matrix used under this fatigue fracture mode. In all cases, the main difference between the composite materials considered in this study is the type of epoxy resin used as the matrix.The test method used to produce the delamination process under mode III fracture is known as the Longitudinal Half Fixed Beam (LHFB) method, used in previous studies by the authors, which was shown to be a valid method for generating the delamination process in composite sheet materials subject to mode III fatigue loading.The experimental data from the fatigue tests were treated with a probabilistic model based on the Weibull distribution. This model facilitates the identification of relevant aspects of the fatigue behaviour of these materials, such as the estimation of fatigue strength for periods of time greater than those tested here, as well as the reliability of the results.The results thus obtained reflect important differences in the fatigue behaviour of the materials under study, the type of matrix being the predominant parameter of the fracture process under mode III loading. Keywords: Delamination, Fracture, Fatigue, Mode III

Se ha analizado la evolución de las propiedades mecánicas, tanto estáticas como dinámicas, de dos composites de matriz termoplástica reforzados con tejido de fibra de vidrio y fibra de carbono, tras mantener inmersas probetas de ambos materiales en una solución de agua oxigenada, empleada en el método TCF, útil en la fabricación de papel. Se observa, desde el punto de vista de la resistencia a tracción, una pérdida de propiedades mucho mayor en el caso del compuesto con fibra de vidrio que en el de fibra de carbono. En cambio, en las curvas correspondientes a la variación de la resistencia a cortadura interlaminar, se aprecia una pérdida muy importante, pero superior para el compuesto de fibra de carbono. Por último, también se mostrará el comportamiento de ambos compuestos a fatiga tras permanencia en la solución de agua oxigenada. Los resultados obtenidos muestran una gran correlación con los generados a partir de los ensayos de tracción.

Several foods are carriers of probiotic bacteria. Most species of the genus Lactobacillus are probiotics and common inhabitants of the human gastrointestinal tract. It is known that they contribute to the health of gastrointestinal tract, but at the same time certain strains can be antagonistic against foodborne pathogens. In this study, we evaluated the effect of Lactobacillus rhamnosus GG on the ability of a strain of Listeria monocytogenes serovar 4b to survive passage through the gastrointestinal tract, and its adhesion and invasion into Caco-2 cells when it was previously habituated on fresh-cut pear stored at 10 °C for 7 days. At the end of the storage, L. rhamnosus GG caused a reduction in the survival of L. monocytogenes in the gastrointestinal tract, and adhesion and invasion into Caco-2 cells. Moreover, it showed an antagonistic activity against L. monocytogenes.

El objetivo de este trabajo es ilustrar el uso del sistema de programas «SAMA» (Sistema Automatizado para el Monitoreo de las Aguas) para la ayuda en el control de la composición química de la aguas. El mismo se basa en la determinación de ecuaciones de dependencia matemática entre la concentración iónica y la conductividad eléctrica. Ha sido implementado en lenguaje Turbo Pascal para microcomputadoras IBM compatibles. El ejemplo de aplicación que se presenta corresponde a aguas de un acuífera kárstico litoral afectado por la intrusión marina las cuales se usan en el regadío de cítricos.