română ADRIANA RUSU, LUMINIȚA PREDOANĂ, SILVIU PREDA, JEANINA PANDELE CUSU, SIMONA PETRESCU, MARIA ZAHARESCU
Abstract
The Er3+ doped silica–titania or silica-titaniaalumina nanopowders were prepared by sol-gel method that represents one of the most flexible and convenient way to prepare oxide films and nanopowders. The selected molar compositions were un-doped and 0.5%Er2O3 doped 90%SiO2-10%TiO2 and 85%SiO2-10%TiO2-5%Al2O3 systems. Similar compositions were previously used for obtaining films for wave guides applications but the mechanism of the phase formation by thermal treatment of the corresponding gels was not previously approached. The gels obtained by gelation of the solutions were analyzed by thermogravimetric and thermodifferential analysis (DTA/TGA) in order to determine their thermal behavior and by IR spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM) to evaluate their structure and morphology. Based on the results obtained, the gels were thermally treated at 500oC and 900oC. The thermally treated powders were characterized by SEM, FT-IR, X-ray diffraction (XRD) and photoluminescence (PL). The significant influence of the Er3+ on the phase formation was established in both studied systems.
Keywords
sol-gel method, erbium, nanopowders, phase formation
LIGIA TODAN , MARIANA VOICESCU, DANA C. CULIȚĂ, SIMONA PETRESCU, MARIA MAGANU, CRINU CIUCULESCU
Abstract
Sol-gel obtained silica and organo silica particles, doped with rhodamine B (Rh B), with potential applications as sensing platforms for fluorescent pH probes were obtained. The silica matrices were generated by sol-gel method from different SiO2 sources and using different routes: the aqueous one with colloidal silica as precursor and the alkoxide one starting with tetraethoxysilane (TEOS) as such and with different organic functionalities. The product was characterized from structural and compositional point of view (FTIR, UV-VIS, SEM, BET surface area and porosity). The leaching of the dye from the matrices was detected by GC-MS. The fluorescence properties and variation with pH were determined. Structural interconversions of the dye take place as a function of the matrices and pH which influence the maximum absorption and emission wavelength of RhB. The presence of organic substituents in TEOS generates a quenching of the RhB fluorescence.
Keywords
silica/organosilica particles, sol-gel, rhodamine B, fluorescent pH probes
SEBASTIAN MARIAN ZAHARIA, CRISTIN OLIMPIU MORARIU, MIHAI ALIN POP
Abstract
The sandwich panels are frequently used as structural elements in various industrial applications, due to their increased rigidity reported to their weight, but also due to their advantages compared to conventional metallic structures or laminated composite structures. This paper presents the behaviour under static and fatigue regime of two sandwich structures with the same type of Nomex honeycomb core, but with skins made from glass fibre reinforced polymer composites, manufactured through different methods. Likewise, the mechanical characteristics of the two types of sandwich structures were compared and analysed. In this paper the behaviour under cyclical fatigue of the two sandwich structures, subjected to 3-point bending, was tested and predicted by implementing the accelerated testing techniques. The accelerated methodology developed in this paper has determined a significant reduction of the testing time for the analysed specimens. Consequently, the testing time for the GFRP1-Nomex specimens was reduced by 6.35 times, respectively by 7.9 times for the GFRP2-Nomex specimens, which determined a significant cost reduction in the testing of composite sandwich structures. Also, the main failure modes of the sandwich structures, subjected to Charpy impact, were identified and analysed using microscopically analysis.
Keywords
glass fiber reinforced polymer, sandwich panels, bending, fatigue, accelerated testing
COSMIN MIHAI MIRIŢOIU, CRISTIAN OLIVIU BURADA, MARIUS MARINEL STĂNESCU, ALEXANDRU BOLCU
Abstract
In this paper the authors have experimentally determined, using some known methods, the loss and damping factors, equivalent dynamic Young modulus and flexural rigidity for composite sandwich platbands with two types of kevlar honeycomb core (rectangular and hexagonal) reinforced with kevlar-carbon fiber. The experimental procedure is characterized by clamping the platbands at one end, placing an accelerometer at the free end for recording their free vibrations. The samples have a thickness of 4 mm, a length of 335 mm and 60 mm width. The connection between the kevlar-carbon fiber and kevlar honeycomb core is made by using epoxy resin with its hardener. The flexural rigidity values were validated by a static loading experimental montage: the platbands are clamped at one end and free at the other; at the free end a force has been applied and the displacement was measured with a displacement transducer. From the displacement value, the flexural rigidity was obtained. In the end, the authors have obtained that the sandwich platbands with hexagonal honeycomb core have better mechanical properties compared to the ones with rectangular honeycomb core.
Keywords
damping factor, loss factor, Young modulus, kevlar honeycomb, kevlar-carbon fiber
DANUTA MATYKIEWICZ, MATEUSZ BARCZEWSKI, HUBERT PUCAŁA
Abstract
The aim of this study was to verify the influence of the compression molding temperature on thermomechanical properties of the basalt-reinforced poly(lactic acid) (PLA) composites. The thermomechanical properties of the composites were determined in the course of dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), static tensile test and tensile impact strength test. The incorporation of basalt fiber into poly(lactic acid) matrix led to obtaining environmentally friendly composite materials with good mechanical properties. The composite production process carried out at different temperature set-ups (170°C, 180°C, 190°C and 200°C) led to the development of composite materials characterized with favorable mechanical properties and specific structure. The simultaneously realized thermal, thermo-mechanical and mechanical analyses allowed to describe the limitation processes resulting from the application of different compression molding temperatures. The best thermomechanical properties were recorded for the composites pressed at the highest temperature (200°C).
Keywords
poly(lactic acid), basalt fiber, thermomechanical properties, compression molding
CRISTINA DIMA (VĂDUVA), ALINA BĂDĂNOIU, ȘTEFANIA STOLERIU, CRISTIANA DANEȘ
Abstract
The valorization of industrial wastes in the manufacture of composite materials is topical in construction industry. The main objective of this study is to improve the thermal insulation properties of some gypsum plaster composites by it’s partial substitution (5 and 30%wt.) with three types of industrial wastes i.e. polyurethane, rubber and chopped electric cables; the paper present also the influence of wastes on the main properties specific for thermal insulation materials (thermal conductivity, compressive strength, short-term water absorption by partial immersion).
The use of the above mentioned industrial wastes in the composition of gypsum plaster elements determines an improvement of thermal insulation properties (thermal conductivity decrease with 17-23%) correlated with a decrease of compressive strength comprised between 68-87%.
The manufacture of this type of insulation materials can contribute to solving environment issues, decreasing the amount of natural raw material used and valorization of industrial as sustainable sources of alternative raw materials.
Keywords
thermal insulation materials, gypsum plaster, industrial waste, thermal conductivity, properties
ALIM KAŞTAN, HÜSEYIN ÜNAL
Abstract
In this study, polyamide 6 (PA 6) was used as matrix material. Materials with eight different compositions were produced by adding 30% (w/w) polypropylene (PP), 2.5% (w/w), 5% (w/w) and 7.5% (w/w) nanoclay and 5% wt. compatibilizer Kraton (SEBS) to PA 6. Pin-on disc abrasive wear tests were carried out under 5 N load, at 1 m/s sliding speed and 12.5m, 25m, 50m and 75 m sliding distances. Emery papers with grid sizes of 80 and 220 grade were used for the tests. Amount of wear, rate of wear and friction coefficient of the composites were obtained from the tests. Also, this study investigated the effect on abrasive wear of PP, nanoclay and compatibilizer added to PA 6.
Keywords
PA 6, polypropylene, nanoclay, compatibilizer, abrasive wear
SADIK ALPER YILDIZEL
Abstract
Fiber reinforced composites have been widely used for various building purposes. Glass fiber reinforced composite containing white cement, gypsum, silica sand and perlite were analyzed in this research. The flexural strength, shrinkage behavior and the freeze-thaw (F&T) resistance of the composites were examined. It was obtained that the use of expanded perlite and silica sand enhances the shrinkage properties of the composite. Especially, expanded perlite used as the replacement of silica sand at the rate of 15 % has significantly enhanced the mechanical properties of the gypsum added composites against the freeze and thaw (F&T) and the shrinkage effects. Researched composite type and the outcomes of the study can be used in the composite production industry for improving the durability and sustainability.
Keywords
Glass fiber, gypsum, white cement, composite, silica sand, perlite
LIGIA TODAN, DANIELA C. CULIȚĂ, DOREL CRIŞAN, NICOLAE DRĂGAN, JEANINA PANDELE-CUŞU, FLORICA PAPA
Abstract
Mono- and bicomponent coordination compounds of Mg-Zr with tartaric acid were synthesized in an aqueous solution, at two different Mg/Zr molar ratios. Part of the obtained amorphous precursors were thermally treated at 6500C, the other part was calcined at 10000C, forming thus MgO-ZrO2 powders. The structure and properties of the precursors and of the oxide powders were determined by thermal analysis, FTIR, XRD, BET method for surface area and pore volume, CO2 adsorption. The influence of the thermal treatment temperature on the powders characteristics was considered. The coordination modes of the tartaric carboxilic groups in Mg, respectively or/and Zr-containing precursors is dissimilar and the dehydration and crystallization processes in the binary powders differ too. High-temperature ZrO2 polymorphs stabilized at low temperature by including the Mg2+ in the lattice, decrease in content with the raise of temperature, partialy turning into monoclinic zirconia.The specific surface area and porosity as well as the CO2 adsorption properties of the samples treated at 6500C are significantly higher than the ones of the powders calcined at 10000C. The CO2 adsoption efficiency of the binary oxides is lower than the one of MgO but higher when compared to ZrO2, one of the samples showing the best performance, although the Mg/Zr molar ratio in the binary calcined oxides is about the same. The oxide powders were stable at recycling.
Keywords
MgO-ZrO2 oxide powders, tartaric acid complexes, solution-gel, thermal analysis, CO2 adsorption
BIN LUO, WEI HUANG
Abstract
This paper aims to disclose the bending properties of composite slab and base slab made from recycled concrete. For this purpose, our research group created haydites from underground sludge and discarded bricks, and mixed them with steel fibres into steel fibre-reinforced recycled haydite concrete (Concrete A) and steel fibre-reinforced recycled brick concrete (Concrete B). Then, each of the two recycled concretes was casted into a rectangular-finned prefabricated (RFP) base slab, which is known for its excellent rigidity, strong bearing capacity and large contact area. For comparison, another RFP base slab was made from ordinary concrete. After that, ordinary concrete was poured onto the three RFP base slabs, forming three composite slabs. Next, static load tests were performed on full-size specimens on all three RFP base slabs and three composite slabs. Based on the test results, the failure features of the specimens and the synergic effect between old and new concretes were discussed in light of the load-deflection curves, load-bar strain curves, contact area between base slab and upper-layer concrete, load-compressive strain curves and feature parameters. It is concluded that under static vertical load, the base slabs and composite slabs made from recycled concretes shared the same failure process with those made from ordinary concretes; the old and new concretes exhibited excellent bonding and synergic effects; the base plate made from Concrete B boasted the highest bearing capacity and lowest deflection among all base plates and composite plates investigated in our research. The research findings lay a solid basis for the research and application of recycled concrete composite slabs.
Keywords
Recycled aggregates; Bending properties; Rectangular-finned prefabricated (RFP) base slab
HUAWANG SHI, LIANYU WEI, YANCANG LI, RHUIZHEN GAO
Abstract
In order to investigate the fatigue performance and microstructure evolution of glass fiber reinforced plastic mortar (FRPM) pipes under cyclic loading, fatigue test was carried out. In the process of fatigue test, the deflection, crack and crack width of each feature of FRPM were observed and recorded. Then, the micro-structure of original samples was scanned by electron microscope(SEM). Mechanical properties of FRPM pipe is analyzed from the view of microstructure for the specimens before and after fatigue loading. Finally, the fatigue life of FRPM pipe under cyclic loading is predicted. The results show that the residual stiffness of FRPM pipe decreases monotonically with the increase of fatigue times, therefore the stress amplitude or stress level is the main influencing factor. The FRPM pipe has a smaller residual stiffness and shorter fatigue life when being applied higher maximum cycling stress and amplitude. The crack in the FRPM tube without fatigue occurs instantaneously and obviously larger than that after fatigue.
Keywords
mechanical performances, FPRM, microstructure, fatigue properties, SEM
TULAY HURMA
Abstract
ZnS and ZnS:In films containing three different rates of In were produced on glass subtrates heated up to 300±5°C. Structural analyses of the films were done by X-ray diffraction (XRD), Raman and Infrared (FT-IR) spectroscopies. It was determined that the films obtained by ultrasonic spray pyrolysis (USP) method had polycrystalline structure. All observed XRD peaks belong to hexagonal wurtzite ZnS structure. Crystallite sizes of the films were approximately calculated in 4.61-4.63 nm range. SEM images showed that particles have homogeneously distributed and held onto surface. It was observed from the EDS results that the In rate of films increased by increasing In doping in the solution. FTIR spectra revealed presence of four significant peaks. Peak observed around 930 cm-1 corresponded to the Zn-S vibration while, smaller peaks around 3500 cm-1 corresponded to the –OH group of H2O stretching. The aromatic ring C–H bending vibrations gave the peaks around 750 cm−1. The optical properties of ZnS and ZnS: In films were investigated by optical transmittance and reflectance spectra.
Keywords
In doped ZnS film; XRD; Raman; Optical properties
S. SATHISH, K. KUMARESAN, L. PRABHU, S. GOKULKUMAR
Abstract
The research work aspires to analyze the effect of various fillers with flax fiber reinforced epoxy composites. Composites filled with varying weight percentage of different fillers such as silicon carbide, alumina and graphite were fabricated by compression moulding techniques. The effect of alkaline treatment of flax fiber was verified by FTIR analysis. The composite containing 15 wt % flax fiber and 7 wt % SiC gave the better mechanical properties. The optimum SiC for better mechanical properties of this present composite is found to be 7 wt. %. The result of this research indicates that incorporation of flax fiber and 7 wt. % SiC filler significantly enhance the mechanical properties of the composite. We concluded that ceramics filled composites will provide substitute brake pad materials respect to asbestos and synthetic based materials.
Keywords
Flax fiber, SiC, Al2O3, Graphite, FTIR
A.R.KRISHNARAJA, S.KANDASAMY, M.KOWSALYA
Abstract
In this study the mechanical performance of hybrid engineered cementitious composite using polymeric fibers and glass fibers are investigated. Nine different mixes are used in this study, in which three mixes with mono fiber and the remaining mixes are developed with hybrid fiber reinforcement. The hybridation with low and high modulus fibers are engaged to increase the mechanical performance of the engineered cementitious composite. This process has a notable achievement in the direct tensile strength and young’s modulus of the ECC mix. The outcome revealed that, poly vinyl alcohol of volume fraction 0.65% and glass of volume fraction 1.35% displayed significant and reasonable characteristics than the other mixes.
Keywords
ECC, Polymeric fibers, glass fiber, mechanical properties, micro structural studies
RADU MIHALACHE, MIHAELA RALUCA CONDRUZ, IONUȚ SEBASTIAN VINTILĂ, VALERIU VILAG, VIRGIL STANCIU
Abstract
Integration of advanced composite materials with polymeric matrix in aerospace domain (turbomachinery, aircraft structures, spacecraft, satellites) is an area of interest for many researchers, large integrators and manufacturers.
Polymeric composite materials can be defined as heterogeneous materials, obtained by associating, in a directed order, different components, one of them being a polymer.
In this paper the first technological stage in the development of a centrifugal compressor rotor is presented, starting from optimizing an existing version of the rotor considering the autoclave technology, developing the new rotor design, mould design and manufacturing and one blade manufacturing trials using advanced composites precursors - prepregs.
Three composite material precursors were evaluated and HexPlyM49/ 42%/200T2X2/CHS-3K was selected as final material to manufacture the compressor rotor. This decision was based on results obtaind by finite element analysis and experimental analysis. It consists in an epoxy resin reinforced with 3K high strength carbon fibers (3K-CHS), twill 2x2 fabric.
It was concluded that an entire rotor blade can be obtained using the technological process presented and advanced composite materials, however the autoclave technology will be used to manufacture the final compressor rotor.
Keywords
centrifugal rotor, composites, composite rotor, composite blade