Papers by Keyword: Mechanical Performance

Abstract: The basic mechanical performance of glue laminated timber (GLT) reinforced with glass fiber reinforced plastic (GFRP) for structural materials was studied. The differences of mechanical performance of the GLT reinforced with GFRP and the common GLT were compared by the test, and the quantitative influence of reinforcement ratio and arrangement pattern of GFRP on the mechanical performance was investigated. The test results showed that the static bending strength of GLT increased with the increasing of GFRP reinforcement ratio, and the reasonable arrangement pattern of GFRP could improve the internal bonding strength of GLT. The influence of reinforcement ratio and arrangement pattern of GFRP on the elastic modulus was relatively small. Finally, a mathematical model of static bending strength for GLT reinforced with GFRP was proposed, which can consider the influence of reinforcement ratio and GFRP arrangement pattern

Abstract: NiCr20TiAl is a typical age-hardening superalloy with Ni-Cr as matrix and γ′ as strengthening phase. The microstructure and mechanical properties of nickel base superalloy NiCr20TiAl under different heat treatment were examined by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), optical microscope (OM) and mechanical tester. The results showed that superior comprehensive mechanical performance of NiCr20TiAl cast alloy was achieved by 1050°C/8h, air cool (AC) +700°C/16h, AC treatment. The edge cracks problem was resolved by 1150°C/1h, water quench (WQ) solid solution treatment before cold rolling process. The vickers hardness of the alloy decreases from 308 to 148. The vickers hardness of the NiCr20TiAl alloy could be controlled below 250 by 1080°C/2min treatment.

Abstract: Portland cement production leads to significant carbon dioxide emission and greenhouse effect. Magnesium oxide eco-cement, which is a mixture of Portland cement, magnesium oxide and fly ash, may be an alternative production. In this paper, the issue is focused on the carbon dioxide absorption ability and mechanical performance of this eco-cement. Several mix proportions of eco-cement were designed to conduct forced carbonation, strength and expansion tests. Also, microstructure analysis after carbonation was conducted. The results indicate that magnesium oxide eco-cement can efficiently absorb carbon dioxide and carbonation can improve mechanical performance substantially, also expansion of the eco-cement is found to fall within the safe limits and possesses good stability and soundness.

Abstract: The present work analyses the behaviour of different binder matrices in order to implement the addition of paper pulp as reinforcement for cementitious composites and assesses the composites flexural properties with time. To prevent microfibers degradation in high-alkaline environments, lower alkaline matrices may be developed. In the present study ternary binder matrices containing ordinary Portland cement (OPC), gypsum (G) and fluid catalytic cracking catalyst residue (FC3R) are presented for that purpose. To assess the performance of the alternatives matrices, pH and conductivity evolution with time were monitored. Also flexural tests were carried out with the intention of evaluate the efficiency of the matrix to preserve fibres within the composite. According to pH and conductivity results is proved that this ternary system offers lower values at early stages (at 3 days) when compared to OPC systems. This inferior alkalinity might be associated to the better mechanical performance with time of the composites when the ternary matrix is used. After 10 months ageing, all the mechanical properties were higher when compared to composites using OPC. Particularly remarkable is the preservation after ageing of the specific energy and deflection at the modulus of rupture when the low-alkalinity matrices were employed, on the contrary what occurred with samples containing OPC where specific energy and deflection were nearly disappeared.

Abstract: Ecological houses have become very popular lately due to an increasing concern regarding the reduction of the CO₂ emissions generated by the building sector. An ecological house is perceived as a building that enhances the environment rather than degrading it. Straw bale houses are considered to be an ecological and energy efficient solution to the traditional houses. The research aimed to evaluate the use of straw bale in constructions. The experimental work included the mechanical and the hygrothermal behaviour of straw bale, i.e. compression test, moisture content and thermal conductivity determination on a straw bale wall placed in climatic conditions specific for Romania. The research results show a better thermal performance than some of the traditional choices existing on the market. The study provides encouraging insight into considering straw bale solutions as a first alternative to the classical ones.

Abstract: The glass frits were prepared via high temperature melting and water quenching method and nano zirconia powders were synthesized via coprecipitation method. XRD and SEM were utilized to analyze the phase composition and microstructures. The results revealed that when the additive amount of frits was 5%, the samples sintered at 1400 °C for 1 h had homogeneous microstructure.

Abstract: There is a continuous demand for next-generation industrial materials because they offer advantages such as high performance, reliable life cycle, reasonable cost, and ease of mass production. Carbon nanotubes (CNTs), which possess unique properties such as beneficial mechanical, electrical, and thermal properties, as well as chemical stability, have received considerable attention as candidates for reinforcing ultra-high-performance nanocomposites. CNT-reinforced Al alloy matrix nanocomposites were fabricated by mechanical ball-milling and hot-pressing processes. The effects of different CNTs on the mechanical properties of the composites were investigated. The mechanical properties were found to change significantly depending on the type of CNT blended with the matrices. The mechanical performance of the nanocomposites can thus be controlled by using different types of CNT reinforcements.

Abstract: This paper presents the results on the influence of steel fiber on the performance of concrete materials. The performance of steel fiber reinforced concrete was studied through mechanical testing, frost resistance, carbonation and impermeability testing. Experimental results showed that steel fibers can improve compressive and flexural strengths, and especially can significantly improve flexural strength. Frost resistance can also be improved, and the higher the volume of steel fibers added, the more the freeze-thaw cycles that concrete could resist. Furthermore, steel fiber can not only slow down the carbonation rate indirectly, but also improve the impermeability of concrete, and impermeability enhanced with the increase of steel fiber.

Abstract: The objective of this research is the production of concrete with recycled aggregates (RA) from various CDW plants around Portugal. The influence of the RA collection location and consequently of their composition on the characteristics of the concrete produced was analysed. In the mixes produced in this research RA from five plants (Valnor, Vimajas, Ambilei, Europontal and Retria) were used: in three of them coarse and fine RA were analysed and in the remaining ones only coarse RA were used. The experimental campaign comprised two tests in fresh concrete (cone of Abrams slump and density) and eight in hardened concrete (compressive strength in cubes and cylinders, splitting tensile strength, modulus of elasticity, water absorption by immersion and capillarity, carbonation and chloride penetration resistance). It was found that the use of RA causes a quality decrease in concrete. However, there was a wide results scatter according to the plant where the RAs were collected, because of the variation in composition of the RA. It was also found that the use of fine RA causes a more significant performance loss of the concrete properties analysed than the use of coarse RA.

Abstract: This paper presents a self-centering bridge which is simplified as a deformation body ,while mechanical performance is still in the elastic range ,considering the influence of gravity pier ,the upper structure load ,prestressed tendons and dampers, the horizontal load vs. rotation curve of the self-centering bridge is obtained by theoretical derivation . The study for the self-centering bridge presented in this paper indicates that: under the cyclic loading hysteretic curve type is flag-shaped ,the prestressed tendons provide self-centering ability and dampers provide dissipating energy.