română AZZEDINE BENYAHIA, ALI REDJEM, ZINE EL ABIDINE RAHMOUNI, ABDELLAH MERROUCHE
Abstract
Composite materials based on woven Alfa and unsaturated polyester resins were manufactured by hand layup technique. The Alfa fibers were collected from the M’Sila region (Algeria). Different chemical treatments such as mercerization, permanganate, acetylating and dichromate have been used in order to modulate the mechanical properties of these composites. According to tensile and flexural tests, the treated composites showed better mechanical performances compared to their untreated counterparts. Actually, the permanganate treated fiber-reinforced composites showed 43.02 % of increase in tensile strength and 31.59 % in Young’s modulus, while the acetylated fiber-reinforced composites showed maximum improvement in flexural strength of about 23.80 %. Furthermore, the flexural modulus was also improved by 35.7 % compared to the untreated Alfa fiber composites. FTIR characterization of Alfa fibers showed that the quantity of hydroxyl groups (-OH) decreased and the crystallinity index increase by 20.53% after alkali treatment. SEM observations on fibers surface showed that the different chemical treatments modified the fiber which improved the fiber–matrix adhesion.
Keywords
Alfa fibers, composites, chemical treatment, tensile test, mechanical properties.
NASTASIA SACA, LIDIA RADU, CLAUDIU MAZILU, MARIA GHEORGHE, IONELA PETRE, VIOREL FUGARU
Abstract
The main objective of this work is to identify, based on experimental physical characteristics investigation, the grout types with potential capacity of residual radionuclides stabilization into storage container of low level radioactivity waste (LLW).
The grouts matrix based on Portland cement or special cement with lead slag addition and various fillers (limestone, L or pulverized fly ash, PFA) were carried out with river fine sand or lead slag recycled fine sand. The Portland cement /PFA or L ratios have had values of 30/70; 50/50 and 70/30, and cement/sand ratio was of 1/1.
There were tested on the physical characteristics – fluidity which assesses the filling ability of the LLW storage container, the density which reflects radionuclide shielding capacity, the shrinkage correlated with the microcracking potential and mechanical strengths evolution required of the long time secure LLW management.
Keywords
grout, special cement, lead slag, pulverised fly ash, encapsulation, low level radioactivity waste
MÜNIR TASDEMIR , UMUT YERLESEN
Abstract
In this study low density Polyethylene (LDPE)-based composites are prepared using mussel-oyster shell powder as natural filler. Filler contents in the LDPE were 5, 10 and 15 wt%. The mechanical properties of the polymer composites were investigated. Some mechanical properties of low density polyethylene bio composites have effected much by the addition of mussel-oyster shell powder. For example, the results showed that the elasticity modulus, Izod impact strength, hardness and density of composites improved with increasing the mussel and oyster contents. The addition of fillers to the LDPE changed the wear rate of the composites. LDPE filled with a high level content of mussel and oyster showed higher wear rate than pure LDPE under dry sliding. The structure and properties of the composites are characterized using a scanning electron microscopy (SEM). This study has shown that the composites treated with mussel-oyster shell powder as natural additive and as an inorganic particle-filled polymer will be attractive due to their improved mechanical properties of LDPE.
Keywords
low density polyethylene, mussel, oyster, mechanical properties, wear
IOSIF HULKA , VIOREL AUREL ŞERBAN, DRAGOŞ UŢU, NARCIS MIHAI DUŢEANU, ALEXANDRU PASCU, IONUŢ ROATĂ, IOANA MAIOR
Abstract
Laser cladding NiCrBSi composite coatings were deposited on the surface of stainless steel substrates using different scanning speeds. The influence of scanning speed on dilution rate and the coatings microstructure were investigated by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and X-ray diffraction. Analysis of microhardness, porosity and the wear behaviour of the obtained coatings were revealed. The coatings were analysed and finally compared to each other. It was found that the microstructure and wear resistance of the coatings were influenced by the scanning speed and dilution.
Keywords
laser cladding, coatings, wear resistance
CRISTINA-ELISABETA PELIN (BAN), ECATERINA ANDRONESCU, GEORGE PELIN, ADRIANA ŞTEFAN, ROXANA TRUŞCĂ
Abstract
In aeronautics applications, there is an increasing interest to replace the use of thermoset matrix in fiber reinforced composites with thermoplastic matrix. This paper presents the obtaining of hybrid carbon fabric reinforced laminated composites based on montmorillonite nanofilled polyamide matrix, using an innovative and cost efficient method involving polymer solvent dissolution, montmorillonite dispersion in different weight contents (1, 2, 4%) relative to the polymer, fabric impregnation with the obtained solution and high temperature pressing. The new laminated nanocomposites were characterized by FTIR spectroscopy to establish nanofiller/polymer chemical interaction, and they were tested in terms of mechanical and thermo-mechanical properties, the fracture cross section being analyzed by SEM and optical microscopy. The hybrid nanocomposites exhibited high mechanical performance, comparable to extensively used carbon fiber reinforced epoxy composites, 4% montmorillonite content generating significant enhancements of both strength and stiffness, as well as heat deflection temperature, results due to both the mechanically improved matrix due to uniformly dispersed montmorillonite, as well a strong fiber/matrix interface due to solvent impregnation processing.
Keywords
carbon fiber fabric, montmorillonite, laminated composites, tensile strength, young’s modulus
GEORGE STANCIU , NICU DOINEL SCĂRIŞOREANU, VALENTIN ION, MARIUS DUMITRU, ECATERINA ANDRONESCU, MARIA DINESCU
Abstract
Calcium doped strontium barium niobate Sr0.5Ba0.5Nb2O6 (SBN:50) is a tungsten bronze ferroelectric material with a tetragonal unit cell. SrxCayBa1-x-yNb2O6 (SCBN) compositions with (x = 0.5; y = 0.14 and 0.28) were obtained by solid-state reaction method. The phase structure, microstructure and dielectric properties of obtained SCBN ceramics were systematically investigated. XRD results showed that SCBN phase with tungsten bronze structure could be obtained in all ceramic samples. Higher Ca content (y = 0.28) lead to occurrence of a secondary phase of CaNb2O6. SEM micrographs show the formation of crystallites with sharp boundaries with an average grain size of about 4 ÷ 12 μm for all SCBN compositions. Compared with pure SBN:50 composition, Ca doping results in a reduction of the dielectric constant value, but the dielectric losses are found to be smaller for this compositions.
Keywords
SBN, SCBN, TTB structure, Dielectric properties
MIHAI BRATU, OVIDIU DUMITRESCU , OVIDIU VASILE, IOAN ROPOTĂ, LUOANA FLORENTINA PASCU
Abstract
Noise is a well known source of environmental pollution in urban areas or at work. Sound pressure level has a harmful effect on human health.
In this paper we present our research on making a new type of composite material and testing its properties of noise attenuation level. Tests were carried out in the anechoic chamber using barrier attenuators of sound waves made of composite material consisting of 50% formaldehyde resin reinforced polypropylene granules formed from waste 50%.
It was also determined the efficiency of the panel by calculating the diffraction pression according to the sound waves dispersion on the acoustic panel’s surface and mapping the attenuation of noise levels due to the composite material..
Keywords
composite materials, waste, acoustic panel, anechoic chamber, sound waves
MĂDĂLINA-ANCA LAZĂR, MIUŢA FILIP, MIHAELA CECILIA VLASSA, LIDIA ADRIANA SORCOI, RADU SEPTIMIU CÂMPIAN, CRISTINA PREJMEREAN
Abstract
The aim of the present study was the elaboration and the characterization of new fiber-reinforced composites (FRCs) that will serve cranial bone reconstruction, particularly in the cases of large bicortical calvarial defects. A series of resins containing dimethacrylate and urethane-dimethacrylate monomers were prepared and characterized. The most promising resin was selected in order to be reinforced with continuous unidirectional and woven E-glass fibers, respectively. The elaborated FRCs were investigated in vitro by scanning electron microscopy (SEM) and by determining the flexural properties and in vivo by intramuscular implantation test. The results of this study pointed out that the FRCs based on urethane dimethacrylic resin reinforced with woven E-glass fibers could be good candidates for the reconstruction of large cranial bone defects.
Keywords
biomaterials, bone reconstruction, fiber-reinforced composite, residual monomer, flexural strength, biocompatibility
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Year
2016
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Issue
46 (2)
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Pages
142-151
S. PERILLI, M. REGI, S. SFARRA, I. NARDI
Abstract
The aim of this work is the study of the thermal flux through a multilayer insulation specimen, whose final panels could be designed for the green building field. The specimen was fabricated using an expanded styrofoam base, the mortar and milk cements, a fiberglass, and hemp fibers chopped and scattered into a surface smoothing. The dimensions of the specimen are 230 x 75 x 30.2 [mm]. The need to analyze a reduced surface in the development of a 3D visualization follows a computational aspect, i.e., to limit the number of degrees of freedom to be solved. Specifically, the research is focused on a comparative analysis among numerical simulations through the data processing by means of Matlab® - using the finite difference method (FDM) in the 1D domain -, and Comsol Multiphysics® - using the finite element method (FEM), both in 2D and 3D domains -. In addition, an experimental analysis centred on the detecting of the sub-superficial fiberglass by means of infrared thermography (IRT) technique is carried out. A specific Matlab® script was also implemented.
Finally, can be observed that Comsol Multiphysics® not only allows a visualization of the flow, as it is done in Matlab®, but also of the entire specimen geometry with the possibility of realizing a video of the thermal transient during the heating and cooling phases.
Keywords
Finite difference method, Finite element method, Infrared thermography, hemp fibers, sub-superficial discontinuities
VASILE MIRON, ENIKÖ VOLCEANOV, GINA GENOVEVA ISTRATE
Abstract
This paper presents a study on the corrosion behaviour of coatings by electroless deposition on the steel strips surfaces. For Ni-P and Ni-P-Al2O3 composite and nanocomposite layers, the variation of corrosion rate in two representative corrosive environments: an acid environment (H2SO4 solution of 5% concentration) and basic environment (NaOH solution of 10% concentration), it has been established, respectively. The corrosion rate was appreciated by using the gravimetric method (mass loss) reported to the area submitted to corrosive attack and the process duration. The study was conducted over a period of 7 days (168 hours) for the acid environment and 28 days (672 hours) in basic environment. The macroscopic appearance of the corroded surfaces was also investigated. The experimental results have emphasized a better behaviour in basic environment of composite coatings, comparatively with the Ni-P coatings with high phosphorus content. In acidic environment, a remarkable behaviour presented the composite Ni-P-Al2O3 and Ni-P alloy coatings, while samples with nanocomposite coating of Ni-P-Al2O3 were completely destroyed.
Keywords
electroless deposition of steel strips surfaces, composite coatings
IULIANA HUDIȘTEANU, NICOLAE ȚĂRANU, IOANA-SORINA ENȚUC, SEBASTIAN GEORGE MAXINEASA
Abstract
Composite structures subjected to complex states of stresses require tailored strength and stiffness characteristics in certain directions, while the properties of the unidirectional lamina are disproportioned and unequal in different directions. Therefore, a multi-layered composite is needed, with various stacking sequences of elementary laminas and different fibre orientations. An accurate prediction of the elastic engineering constants is essential, in order to evaluate the stiffness properties of composite laminates.
The paper presents a comparative analysis of the in-plane elastic engineering constants of continuous fibre reinforced laminated composites, pointing out the influencing parameters of the stiffness properties of multi-layered composites. Three types of laminates, made of composite laminas reinforced with S glass fibres or E glass fibres, embedded in an epoxy resin, with different geometric arrangements of laminas are analysed: an asymmetric general laminate, an anti-symmetric angle-ply and a symmetric angle-ply laminate. The obtained results, illustrated by the graphical distributions of the engineering constants, reveal superior stiffness properties in case of particular laminates.
Keywords
in-plane engineering constants, composite laminates, fibre orientation, glass fibres
MAHAMMADALI A.RAMAZANOV, ABEL. M.MAHARRAMOV, FLORA V.HAJIYEVA, FEYZA KIRAÇ, OLGUN GÜVEN
Abstract
In the present work, thermal and mechanical properties of nanocomposites PP+ZrO2 are studied. The presence of zirconium dioxide in PP increases its thermal stability and mechanical properties of nanocomposites. The AFM studies show that a change in upper molecular structure of polypropylene as well as a chipping of structure elements of surface morphology occur with addition the nanosize powder to the polymeric matrix. The thermal stability and mechanical properties generally increases with increasing amount of zirconium dioxide. Improvement in thermal stability of PP occurs by the addition of 5% ZrO2. It was experimentally shown that increasing of volume content of ZrO2 changes the mechanical durability of nanocomposite PP+ZrO2 with extremum, i.e. the concentration of ZrO2 up to 5% increase durability, and more than 5% decrease it. These results prove that ZrO2 nanoparticles with concentration up to 5% are the centers of structure nucleation, and further increasing of nanoparticles concentration leads to destroying of physical structure of polypropylene.
Keywords
Nanocomposites, mechanical properties, strength, mechanical testing, thermal analysis
D.N. ISOPESCU, L. DUMITRESCU, I.D. ZĂPODEANU, O. NECULAI
Abstract
The paper findings are focused on the embodied impacts of building materials and component combinations that influence, generally, on the environment, and, particularly, the greenhouse gas emissions of a case study based on a new developed hybrid building system applicable to low-rise buildings located in seismic zones. The hybrid system has been designed as a masonry made of autoclaved aerated concrete blocks strengthened with composite frames made of rolled steel profiles embedded in concrete. The results obtained in design calculus, those obtained for global coefficient for thermal insulation, and those obtained in Life Cycle Assessment, have highlighted the good performance of the proposed hybrid system regarding its environmental impact.
Keywords
greenhouse gas emissions; Global Warming Potential; hybrid structure; Life Cycle Assessment; energy efficiency; low-rise buildings for seismic zones
Coating magnetite nanoparticles with mesostructured silica shell of different pore size and geometry
RAUL-AUGUSTIN MITRAN, DOINA GEORGESCU, NICOLAE STĂNICĂ, CRISTIAN MATEI, DANIELA BERGER
Abstract
Composite nanomaterials combining magnetic properties and porosity have various applications as catalysts, in targeted drug delivery, depollution, energy storage etc. However, the synthesis of magnetite nanoparticles coated with SBA-16-type mesoporous silica is very challenging due to the acidic medium required, which leads to the dissolution of iron oxides. Here, we report a simple synthesis of Fe3O4@SBA-16 composite with high content of magnetic nanoparticles in a weak acidic medium. The influence of reagents addition order was also studied. The resulting materials have been investigated by small- and wide-angle X-ray diffraction, infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, nitrogen sorption analysis and magnetic measurements. The properties of Fe3O4@SBA-16 samples are discussed and compared with a Fe3O4@SBA-41 material, obtained in basic medium. All magnetic composites present high porosity and superparamagnetic behavior.
Keywords
superparamagnetic, mesoporous silica, SBA-16, Fe3O4@SBA-16, magnetite, MCM-41
GEORGE PELIN, ECATERINA ANDRONESCU, CRISTINA-ELISABETA PELIN, OVIDIU OPREA, ANTON FICAI
Abstract
The paper presents a study regarding obtaining, characterization and testing of carbon fiber felt-phenolic resin composite and nanocomposite materials with neat phenolic matrix and nanofilled with silicon carbide nanoparticles added in two different weight contents (1 and 2 wt. %). The effect of the nSiC presence and content is evaluated taking into consideration mechanical, tribological and thermal behavior. Mechanical testing consisted of compression and 3-point bending tests, the results indicating that the strength and stiffness are improved in the case of nanofilled sample. Tribological testing illustrated that friction coefficient increased with nSiC content increase. Thermal behavior was evaluated by TG-DSC analyses and thermal shock tests (at 1100°C), the post-test mass loss analyses showing that nSiC is able to act as a thermal protection agent, improving thermal resistance of these materials. The experimental results indicate that adding silicon carbide nanoparticles in the phenolic resin matrix of carbon fiber felt based ablative type materials improves their mechanical, tribological and thermal properties and recommends them as potential candidates for ablative applications.
Keywords
carbon fiber felt, ablative materials, nano-silicon carbide, thermal shock resistance, TG-DSC
YU HAN, BAO-MIN WANG , SHUAI LIU
Abstract
Mechanical performances of carbon nanotubes reinforced cement-based composites have been studied separately. The autogenous shrinkage of cement-based composites doped with multi-walled carbon nanotubes (MWNTs) were investigated with low MWNTs concentration of 0, 0.05%, 0.1% and 0.15% by weight(wt%) of cement in the early age in this paper. Ultrasonic processing and a commercially surfactant were utilized to achieve homogenous MWNTs suspensions. The addition of MWNTs decreased the autogenous shrinkage of cement composites compared to the reference sample. When the MWNTs dosage was 0.15 wt%, the autogenous shrinkage of specimen was the minimum, which was 28% lower than the reference sample. The water-cement ratio affects the early-age autogenous shrinkage more obviously. The results indicated that MWNTs can also have a beneficial effect on the early strain capacity, the early-age and long term durability of the cement-based composites
Keywords
Multi-walled carbon nanotubes; cement-based composites; durability; early-age autogenous shrinkage
VLAD LUPĂȘTEANU, NICOLAE ȚĂRANU, PETRU MIHAI, GABRIEL OPRIȘAN, RADU LUPĂȘTEANU, DRAGOȘ UNGUREANU
Abstract
The interface behaviour of carbon fibre reinforced polymer composite (CFRP) strips bonded to steel surfaces is a key aspect in assuring an efficient strengthening solution for structural or non-structural steel elements.
The experimental program which is presented in this paper was developed at the Faculty of Civil Engineering and Building Services from Iasi, and it focused on the investigation of the behaviour of the CFRP-to-steel bonded interfaces. A number of 25 single lap shear specimens were prepared and tested up to failure. The parameters considered in this study were: the type of the CFRP composite strip, the type of the adhesives and their thicknesses. In addition, the influence of the surface preparation was analysed by comparing the results obtained for specimens with grit-blasted steel surfaces and for untreated ones. The specific failure modes were identified and commented on the basis of the performed tests; the load-displacement curves were plotted and the strain distributions along the bond lengths were investigated at different load stages.
Keywords
CFRP composite strips, steel, interface behaviour, bonded single lap shear joints