[en] Fiber reinforced composites are widely used in industrial applications due to their high strength, light weight and ease in manufacturing. In applications such as automotive, aerospace and structural parts, the components are subjected to unwanted vibrations which reduce their service life, accuracy as well as increases noise. Therefore, it is essential to avoid the detrimental effects of vibrations by enhancing their damping characteristics. The current research deals with estimating the damping properties of Glass fiber reinforced epoxy (GFRE) composites. Processing of the GFRE composites is carried out using hand-lay technique. Various design parameters such as number of glass fiber layers, orientation of fibers and weight ratio are varied while manufacturing GFRE composites. The effects of variation of these design parameters on damping property of GFRE composites are studied extensively. (paper)

[en] Cellulose nanocrystals (CNC) were isolated from Munguba (Pseudobombax munguba) fibers and then functionalized with octadecyl isocyanate. Nanocomposites based on poly(butylene adipate-co-terephthalate) (PBAT) were prepared with different concentrations of cellulose nanocrystals (3, 5 and 7 wt%). We show that the addition of functionalized CNC leads to PBAT-based nanocomposites with enhanced thermal, rheological and mechanical performances, maintaining the biodegradability of the matrix. The better properties of the nanocomposites were related to the optimal amount and the uniform dispersion of CNC in PBAT. The study here presented expands the application of Munguba fibers, exploring their use to prepare PBAT-based biodegradable nanocomposites with improved properties. These nanocomposites have potential for replacement the conventional polymers in future applications with the advantage of exhibiting biodegradability.

[en] The quasi-static and dynamic mechanical behaviours of the concrete reinforced by twisting ultra-high molecular weight polyethylene (UHMWPE) fibre bundles with different volume fractions have been investigated. It was indicated that the improved mixing methodology and fibre geometry guaranteed the uniform distribution of fibres in concrete matrix. The UHMWPE fibres significantly enhanced the splitting tensile strength and residual compressive strength of concrete. The discussions on the key property parameters showed that the UHMWPE fibre reinforced concrete behaved tougher than the plain concrete. Owing to the more uniform distribution of fibres and higher bonding strength at fibre/matrix interface, the UHMWPE fibre with improved geometry enhanced the quasi-static splitting tensile strength and compressive strength of concrete more significantly than the other fibres. The dynamic compression tests demonstrated that the UHMWPE fibre reinforced concrete had considerable strain rate dependency. The bonding between fibres and concrete matrix contributed to the strength enhancement under low strain-rate compression.

[en] Strength and durability characteristics of geopolymers produced using three precursors, consisting of fly ash, Ground Glass Fiber (GGF), and glass-powder were studied. Combinations of sodium hydroxide and sodium silicate were used as the activator solutions, and the effect of different sodium and silica content of the activators on the workability and compressive strength of geopolymers was investigated. The parameters used in this study were the mass ratio of Na2O-to-binder (for sodium content), and SiO2-to-Na2O of the activator (for silica content). Geopolymer mixtures that achieved the highest compressive strength from each precursor were assessed for their resistance to alkali-silica reaction and compared against the performance of portland cement mixtures. Test results revealed that GGF and fly ash-based geopolymers performed better than glass-powder-based geopolymer mixtures. The resistance of GGF-based and fly ash-based geopolymers to alkali-silica reaction was superior to that of portland cement mixtures, while glass-powder-based geopolymer showed inferior performance.

[en] Magnetorheological elastomers (MREs) are a group of smart materials which have many applications such as dynamic vibration absorbers, engine mounts, and so on. The damping behavior is important for applications of MREs. However, the mechanism of the damping of MREs has not been investigated thoroughly. In this study, MREs are modeled as special particle reinforced composites with magneto-induced properties and the mechanism of the damping behavior of MREs is investigated theoretically and experimentally. It has been found that there are three types of damping property in MREs: the intrinsic damping, the interface damping and the magneto-mechanical damping. The presented damping model is successfully validated by damping tests on a series of MRE samples. Furthermore, the relationships between the damping properties and formulas of MREs are discussed; this provides guidance for the manufacture of MREs with various damping properties. (paper)

[en] The asphalt surface layer is the most exposed to weather and traffic conditions on roads, especially those subjected to winter maintenance. Therefore, a deep knowledge of the mechanisms which can damage this layer is necessary to improve its design, construction and long-term use. With this purpose, two types of asphalt mixtures used on roads from NW Spain were subjected to durability tests (freezing-thaw and thermal-stress) with a saturated NaCl solution. After the durability tests, a wheel tracking test was performed on the samples, and the resultant material was analyzed by optical polarized light and fluorescence microscopy. This analysis showed that the binder-aggregate low adhesion was the main responsible of the asphalt mixture damage. This damage was concentrated in the aggregates because the binder acted as an impermeable wall. Consequently, the NaCl solution penetrated and degraded the aggregates quickly and strongly.

[en] A radiometric measuring method is described of the spacing and the depth of embedding of metal reinforcements having the atomic number Z₁, e.g., steel wire ropes, reinforcing a material having the atomic number Z₂, such as rubber conveyor belts. It is assumed that Z₁>Z₂ and Z₂<20. Backscattered gamma radiation is used in simultaneous measurement of the spacing and the depth of embedding of the reinforcements in material. The measurement may be conducted by placing the Z₂ atomic number material on a support of the same material whose thickness is always such that a saturated layer may be obtained. (B.S.)

[en] Corrosion of the reinforcing steel may cause significant loss of strength of reinforced concrete structures. The study focuses on accelerating such corrosion and examining the degradation of (i) the compressive strength of concrete due to sodium sulfate in a wet atmosphere; and (ii) the flexural strength by a solution of sodium sulfate and sodium chloride. Three types of concrete were used and different beam specimens were reinforced by steel rebars of different diameters (6, 8 and 10mm), part of the beams being pre-cracked. The concrete with least strength allowed higher sulfate penetration along the entire process and the compressive strength increased slightly, possibly due to lower porosity of concrete after contamination. The results of the flexural tests showed decrease of strength in all cases. Pre-cracked beams exhibited smaller influence of porosity of concrete. Beams with 6mm rebars showed the largest loss of strength due to the contamination and corrosion process

[en] Earthen materials and Rammed Earth in particular have been practiced since immemorial time by different civilizations and is still present, for instance currently a 1,7 billion of people live in constructions made with these technics [1]. The increasing interest of the sustainability Rammed Earth properties, beside the low cost and comfort values are making of this method a viable construction [2]. The Rammed Earth innovations implies the use of additives, in order to improve the earth qualities providing a higher stability values and prevent the atmospheric agents [3]. Therefore the use of natural additive such as starch or artificial materials like cement will be analysed. In addition, the structural improvement by using steel reinforcements has been a significant advantage for the Rammed Earth mechanical behaviour [4]. The moisture content in the Rammed Earth is a key factor that can be controlled according to the Relative Humidity, soil content, drying place and additives addition. Taking into consideration that the Rammed Earth is a traditional method, the regulation for these constructions has not a standard worldwide, instead of this it´s use locals or regionals regulations The aim of this study is to analyse the traditional Rammed Earth (TC) in comparison with a Rammed Earth with steel reinforcement (TRA), including the use of additives (natural and artificial) in the soil mixture. The Rice Starch from the plant Oryza sativa (GOVA) was selected as a natural additive while the artificial additive is the Portland cement. Therefore it was selected five different samples [5] [6] [7] [8] [9] and evaluated base Sample Module of 200cm3 created for this study, due to all the samples has different study conditions e.g. shapes or sizes

[en] Highlights: • Concepts to adjust the delamination behaviour of fibre reinforced composites are investigated. • The interlaminar interfaces are modified by inserting perforated foils. • Mode I and II energy release rates are determined. • A function describes the correlation between energy release rates and the level of perforation. • The findings are used to tailor the structural energy dissipation capacity deformation response. Concepts to adjust the delamination behaviour of textile reinforced composites are investigated. The composite interfaces are modified by adjusting the interlaminar contact area using perforated PTFE-foils. According mode I and mode II energy release rates are determined and a progressive correlation between the interlaminar contact area and energy release rates is identified. The results are exploited within three point bending experiments to adapt the structural delamination and subsequent energy dissipation behaviour with the proposed interface modification concept. Two structural designs concepts are evaluated numerically: adjusting structural energy dissipation capacity and adjusting the peak levels as well as the characteristic trends of the structural reactive forces. It is demonstrated, that the mechanical response of composite structures can be tailored by controlling their delamination behaviour.