Building insulation is commonly realized using materials obtained from petrochemicals or from natural sources processed with high energy consumptions, causing significant harmful effects on the environment. The "sustainability" applied to building design has encouraged many researches to develop thermal and acoustic insulating materials using natural or recycled materials. Many natural materials were already used in ancient times to thermally insulate the dwellings and to give resistance: straw and reed are some representative examples. Aim of this paper is to evaluate the influence of reed stems and straw on the thermal and mechanical performances of cement. To reach this, several types of mixes were prepared: a specimen as reference mix without any addition of fibers and some more specimens with reed only, with straw only, and finally the combination between straw and reed in different percentage. The tests were performed to determine the thermal conductivity, the compressive and flexural strength of the cement mortar panels. The results showed that straw, if combined with reed stems, could be considered as a valid reinforcement in a cementitious matrix characterized by enhanced thermal insulation and good mechanical properties. ENEA researchers have also applied a statistical method to the obtained test results in order to develop a predictive model of compression and flexural behavior of fiber-reinforced specimens with different percentages of organic fibers in the mixture cementitious.
Ti-6Al-4V is an alloy that is increasingly used in aeronautics due to its high mechanical properties coupled with the lightness. An effective technology used to manufacture titanium components with a reduced buy to fly ratio is the laser beam welding. Previous studies showed that the key factor that rules the mechanical properties and the fatigue life of the joint is its morphology. The aim of this paper was to investigate the influence of the main process parameters, such as welding speed and laser power, on the geometrical features of the joint, in terms of undercut, underfill, reinforcement and so on. 3.0 mm thick Ti-6Al-4V rolled sheets were welded in butt joint configuration by using a Nd-YAG laser source. The joint performances were studied in terms of weld morphology, microstructure and Vickers microhardness. Then, defects such as underfill and reinforcement, controlling the whole weld morphology, were observed, and the relationship between the occurrence, the entity of these defects and the process parameters was studied.
Different layers of different thicknesses were coated on the same polymethyl methacrylate (PMMA) substrate. For each of these bilayered systems, quasi-static and dynamic instrumented indentations using continuous stiffness measurement have been made. We verified if data from indentation tests performed on a given sample obey a power law relationship. The aim was to calculate the viscoplasticity index n with sufficient accuracy (by taking into account the viscoelastoplastic properties of the studied samples), since this value is characteristic of the viscoplastic properties of a material and, therefore, allows evaluating the plastic scratch resistance of the surface. Thanks to both indentation methods the viscoplasticity index could be calculated and its value compared to the different bilayered systems one. As n is supposed to be intrinsic to a material, its value should not depend on the characterization technique.
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