Band 26, Heft 1

The effects of units, material parameters, and constitutive relationships on the dynamic mechanical response of composite laminates subjected to high- and low-velocity impacts were investigated. Additionally, the role of impact or shape, including hemispherical, flat, and conical, on the damage area of the adhesive layer and displacement of the center of the laminated plates was investigated. The results show that the energy absorption of composite laminates increases with impact velocity, and specific energy absorption changes with the density of the contact surface, which is affected by ply thickness. Moreover, the target energy absorption decreases with increasing layer angle. Under a low-velocity impact, the maximum contact force, damage area of the adhesive layer, and displacement of the center of the laminated plate increase as the impact energy increases, thus showing that impact energy is not directly related to contact duration and energy absorption of composite laminates. The results of different geometric shapes show that the damage area of the adhesive layer and the displacement of the center of the laminated plates are largest for a conical impactor and smallest for a flat impactor.

The bond strength between fibre-reinforced polymer (FRP) rebars and concrete is one of the most significant aspects of composite behaviour for rebars and concrete. In this study, a database of 408 beam type specimens consisting of beam end specimens, beam anchorage specimens and splice beam specimens was compiled from the current literature and used to develop a simple prediction using the artificial neural network (ANN). The data used for modelling were organised in a format of eight input parameters that include FRP type, cover bar surface, confinement, bar diameter ( d b ), concrete compressive strength (fc)$(\sqrt {{f_c}} )$, minimum cover-to-bar-diameter ratio ( c/d b ), bar-development-length-to-bar-diameter ratio ( l/d b ), and the ratio of the area of transverse reinforcement to the product of transverse reinforcement spacing, the number of developed bars and bar diameters ( A tr /snd b ). Additionally, a simple prediction formula by regression analysis was developed. The root mean square error and R 2 values of the testing data were found in order to compare the results of both ANN and the proposed model with existing regulations. The new ANN model predicts the bond strength of FRP bars in reinforced concrete with 0.8989 R 2 , thus yielding better results when compared with existing regulations.

This paper presents the experimental behavior of plane, non-strengthened and glass fiber reinforced polymer (GFRP) strengthened infilled reinforced concrete (RC) frames with low strength concrete (LSC) and normal strength concrete (NSC) under lateral reversed cyclic loading. For this purpose, eight full-scale, one-bay, one-storey plane and infilled (brick and aerated concrete blocks which are commonly used in RC construction) RC frames with LSC and NSC were produced and in-plane lateral loading tests were carried out. Test results indicate that infill walls considerably change the behavior of frames by increasing rigidity and load carrying capacity. By contrast, GFRP fabric used for strengthening of infilled RC frames improves ductility, load carrying and energy dissipation capacity of infilled frames with LSC and NSC as well. After all the test results were evaluated together, a GFRP strengthened brick infilled frame demonstrated the best performance under cyclic lateral loading.

Basalt fiber-reinforced polymer (BFRP) bars have been increasingly applied to offshore structures, which are subjected to seawater corrosion and wet-dry cycles during their service time. This study evaluated the alkali-salt resistance performance of BFRP bars with different resin matrix types under wet-dry cycles. The tensile and shear strength of BFRP bars were tested. As a comparison, experiments of BFRP bars under continuous immersion were also conducted. The mechanisms of the two different conditions were analyzed by scanning electron microscopy (SEM). A relationship was established between the degradations under continuous immersion and wet-dry cycling. The results demonstrated that the alkali-salt resistance of vinyl resin matrix BFRP bars was superior to that of epoxy resin matrix BFRP bars under wet-dry cycles. Furthermore, according to the data obtained under continuous immersion, a time shift factor for predicting the durability of BFRP bars under wet-dry cycles was proposed.

Reinforcement particle size is very important for the performance of metal ceramic composites. This work studied the influence of B 4 C particle size on the mechanical properties of Al matrix layered composites. These composites were fabricated using a simplified semicontinuous casting and hot-rolling process. To obtain an optimized filling structure of particles, Horsfield filling principle was applied to determine the size and mass fraction of B 4 C particles. Four sizes of B 4 C particles were used with various combinations. The results showed that with the increase of the B 4 C particle size and fine B 4 C mass fraction, the hardness of the composites decreases whereas the impact strength and ultimate tensile strength increase. The residual stress at interface should be responsible for the variation in properties. Besides, the interparticle distance also contributes to the change in impact strength and ultimate tensile strength.

Ba 1−x Ce x Ti 1−y Mn y O 3 (where x and y varies from 0.00 to 0.03) ceramic samples are synthesized by conventional solid state reaction technique. The samples are sintered at 1473 K for 4 h. The grain size is observed to increase with increasing dopant and co-dopant concentration. The X-ray diffraction confirmed the cubic phase of these BaTiO 3 -based ceramics with a small amount of secondary phase. The current density shows a nearly linear relationship with voltage, and the AC resistivity of the samples is observed to decrease with increasing frequency and doping concentration. The dielectric constant and dielectric loss were observed to decrease with frequency in the lower frequency range (0.2–10 kHz), but remained almost the same at the high-frequency region (>10 kHz). Though Ce-doped samples shows better dielectric properties than Mn-doped samples, the Ce-Mn co-doped samples, having improved their dielectric properties, can be used to fabricate different optoelectric devices.

A multiscale finite element method is adopted in this paper to study the vibrational characteristics of polymer matrix composite plates reinforced with the combination of carbon fibers (CFs) and carbon nanotubes (CNTs). The effects of nanoscale and microscale are coupled through a two-step procedure. In the first step, random dispersion of CNTs into the polymer matrix is modelled using a three-phase representative volume element (RVE). In the selected RVE, the influence of the interphase formed because of non-bonded interactions between the polymer matrix and CNTs is taken into account. In the second step, the distribution of CFs into the composite is modelled, and the elastic properties of CF-CNT-polymer matrix hybrid composite are calculated for various values of volume fractions of reinforcement phases. Then, the free and forced vibration behaviors of composite plates are analyzed. It is considered that the plates have rectangular, circular, and annular shapes and are under clamped/simply supported edge conditions. The effects of CNT/CF reinforcement on the elastic modulus and density of composite and on the free/forced vibration response of the considered structures are investigated. It is shown that the vibrational behavior of plates is significantly affected by the hybrid reinforcement with CNT and CF.

To improve the wear resistance of polyurethane (PU) coating and its adhesion to the steel substrate, a series of simple and practicable techniques were designed to mix nano-SiO 2 with PU powder to cast a coating layer onto the steel. When the addition of nano-SiO 2 was small, a network structure of PU-SiO 2 was produced. It improved the wear resistance of the composite coating and its adhesion to the steel substrate. When the addition of nano-SiO 2 was excessive, agglomerated nano-SiO 2 particles not only affected the bond between the PU resin and the steel substrate but also became abrasive materials, intensifying the abrasion of the composite coating during friction. It resulted in lower bonding strength and poorer wear resistance of the composite coating. The wear rate and friction coefficient of 2 wt.% SiO 2 /PU composite coating were 1.52×10 −6 cm 3 /min N and 0.31, respectively. Its wear resistance was about 10 times as high as that of the pure PU coating. Furthermore, a simple and practicable installation was designed to test the bonding strength between the coating and the steel substrate. The bonding strength between 2 wt.% SiO 2 /PU composite coating and the steel substrate was 7.33 MPa, which was 39% higher than that of the pure PU coating.

In the present work, the effects of adding nanoalumina and marble dust on the wear behavior of dental composites were investigated. The hardness of dental composite was determined using Vickers micro-hardness tester. A two-body abrasive wear test was performed on the dental wear simulator under the medium of artificial saliva. The experiments were performed as per the Taguchi orthogonal array and steady state condition by varying parameters such as filler content, normal load, sliding velocity, and number of cycles. The hardness results indicated that the incorporation of 5 wt. % of nanoalumina increased the hardness of the dental composite by 12%, whereas the incorporation of 5 wt. % of marble dust increased the hardness of the dental composite by 7%. Also, for the experiments as per the Taguchi orthogonal array, the mean volumetric wear in the case of nanoalumina-filled dental composite was 9.6% less than that of marble dust-filled dental composite. However, in both the cases, the volumetric wear increased with the increase in normal load, sliding speed, and number of cycles but decreased with the increase in filler content. Analysis of variance (ANOVA) of the results indicated that normal load was less significant compared to filler content, sliding speed, and number of cycles.

This work focuses on polyvinyl alcohol (PVA) biodegradation in the presence of mineral clays in an aqueous aerobic environment. PVA with a degree of hydrolysis of 88% and 72% was used for the experiments. The selected group of mineral clays (nanofillers for polymers) of montmorillonite (MMT) Cloisite ® Na + ; organo-modified montmorillonite (OMMT) Cloisite ® 20A, Cloisite ® 30B; waste kaolin; kaolin; and zeolites were prepared by synthesis of the aforementioned kaolins. The level of biodegradation was measured using a respirometer, Micro-Oxymax, and evaluated according to CO 2 production. Results of this test indicate a negative effect on PVA biodegradability in the presence of MMT Cloisite ® Na + and Cloisite ® 30B. It has been found that PVA biodegradability in the presence of no adapted inoculum was adversely affected by the biocidal effects of the organic modifier of Cloisite ® 30B. In this case, PVA 88-8 biodegradation decreased by 71% and PVA 72-10 biodegradation dropped by 58%. Furthermore, the sorption of PVA on the Cloisite ® Na + in the range of 40%–45% was demonstrated in the following research.

ZnO is modified by Cu 2 O by the process of precipitation and calcination. X-ray diffraction has shown that Cu 2 O/ZnO catalysts are made of highly purified cubic Cu 2 O and hexagonal ZnO. Scanning electron microscopy and transmission electron microscopy have shown that ZnO adhered to the surface of Cu 2 O. Due to the doping of Cu 2 O, the absorption range of the Cu 2 O/ZnO catalyst is shifted from the ultraviolet to the visible region due to diffuse reflection. X-ray photoelectron spectroscopy and photoluminescence spectra have confirmed that there is a substantial interaction between the two phases of the resultant catalyst. The degradation efficiency of Cu 2 O/ZnO on methyl orange solution is obviously enhanced compared to Cu 2 O and ZnO. The maximum degradation efficiency is 98%. The degradation efficiency is affected by the pH of the solution and initial concentration. After three rounds of recycling, the degradation rate is almost same. This shows a consistent performance of Cu 2 O/ZnO. The increase in catalytic ability is related to the lattice interaction caused by the doping of Cu 2 O.

Wood-plastic composites (WPC) were manufactured from polypropylene, wood flour, maleic anhydride grafted polypropylene and organoclay. The sub-surface mechanical properties and the sub-surface creep behavior of the organoclay-based WPC were examined by the nanoindentation technique. The results showed that the hardness, elastic modulus and creep resistance of the WPC enhanced with the loading of C20 organoclay. This enhancement was subject to the organoclay content and the dispersion of organoclay in the polymer matrix. The hardness, elastic modulus and creep resistance of WPC with 1 wt% organoclay content enhanced by approximately 36%, 41% and 17%, respectively, in contrast with WPC without organoclay. To study the impact of organoclay content on the creep performance of WPC, a viscoelastic model was actualized. The results demonstrated that the model was in good agreement with the experimental information. Reinforcement of organoclay prompts expansion in elastic deformation and instigates a higher initial displacement at the early stage of creep.

In this work, wire electric discharge turning, a novel and unconventional technique, was used for the turning operation of a newly developed hybrid metal matrix composite of aluminum (A359/B 4 C/Al 2 O 3 ) fabricated in-house by electromagnetic stir casting. The objective of the work was to examine the effect of rotational speed on the elements of surface integrity. It involved the measurement of various parameters such as the roughness ( Ra , Rq , Rz ), morphology of the recast layers, microhardness variation, and the formation of residual stresses on the machined surface and in the subsurface during the operation. The quality of the turned surface was examined by 3D surface visualization images and surface topographical details obtained by an Olympus LEXT OLS 3100 laser confocal microscope. Further, surface study at the microscopic level was done by field-effect scanning electron microscopy (FE-SEM) images to examine the surface defects. The measurement results revealed a successful turning operation, which showed a dull, textured surface without any specific texture or pattern on the machined surface. The surface had many peaks and valleys with small-scale of defects such as surface porosity. However, these defects were negligible and resulted in a smooth surface finish at high rotational speeds.

The paper is devoted to finite element method based study of stress field heterogeneity at microstructure level of two-phase cemented carbides. Special attention is put on investigation of influence of the microstructure model type on the stress field distributions. Two- and three-dimensional models of the microstructures have been generated. Moreover, two different representations of the microstructure have been considered. The first one assumes uniformly distributed cobalt phase forming continuous boundaries between tungsten carbide particles. The second one assumes that the cobalt phase shape and distribution are created in a way that allows for no differentiation of continuous boundaries between tungsten carbide grains. Finite element analyses have been carried out with different microstructure models. The results of the simulations are stress distributions in each phase of the material. Furthermore, a numerical homogenization has been conducted to investigate the phase properties’ influence on the effective elastic constants of the cemented carbide.

The present study investigates the influence of graphene nanopellets (GnPs) on the damping and vibration characteristics of fiber-reinforced basalt/epoxy composites for different weight contents of GnPs particles (0.1, 0.2 and 0.3 wt%). The variation of dynamic properties in terms of loss and storage modulus was explored by using the experimental modal analysis. The damping properties were determined by using logarithmic decrement method from the acceleration-time envelope curves. Results showed that the incorporation of GnPs at weight contents of 0.1% and 0.2% significantly affected the damping and vibration characteristics of the samples as a result of the interfacial strength between the GnPs particles-fiber-matrix interactions. The natural frequencies increased by 20.7% and 25% at GnPs contents of 0.1 and 0.2 wt%, whereas the damping ratios increased by 28.5% and 57.1%, respectively.

In order to improve the drawbacks related to hydrogels, nanocomposite hydrogels were developed by incorporating different types of nanoparticles or nanostructures in the hydrogel network. This review categorizes nanocomposite hydrogels based on the type of their nanoparticle into four groups of carbon-, polymeric-, inorganic- and metallic-based nanocomposite hydrogels. Each type has specific properties that make them appropriate for a special purpose. This is mainly attributed to the improvement of interactions between nanoparticles and polymeric chains and to the enhancement of desirable properties for target applications. The focus of this paper is on biomedical applications of nanocomposite hydrogels and the most recent approaches made to fulfill their current limitations.

The force-electric coupling relationship of the mechanical and electrical properties of piezoelectric composites has been the main factor in the research and development of piezoelectric composites in practical application. A novel orthotropic piezoelectric composite material (OPCM) element is studied in this paper. The properties of the piezoelectric phase and the polymer phase and the influence of the geometrical dimensions of the OPCM on the longitudinal wave drive element are analyzed from the perspective of mechanics and electric power, respectively, and the structural design is optimized. This provides a theoretical basis for the development of OPCM and of new longitudinal ultrasonic phased array actuators.

POSS-coated wollastonite composite particles were prepared by the liquid phase mechano-chemical grinding of wollastonite and POSS powder together in the high pressure homogenizer [1, 2, 3, 4] for the first time. And then we prepare UV curable coatings of vinyl trimethoxy silane(VTMS) / butyl acrylate (BA) with different content of composite particles [5]. Nuclear magnetic resonance spectroscopy, scanning electron microscopy and infrared spectra were used to investigate the microstructures and morphologies of the composite. The properties of the coatings are tested by FTIR, SEM, water contact angles and so on. The results indicate that the POSS was successfully loaded on the surface of silica fume to prepare composite particles and when the addition of the composite particles is 12%, the water contact angle of the UV curable coating reaches 151.96 ∘ , and the mechanical properties of the coating are also qualified.

Preload is the primary reason why pre-tightened tooth connections (PTTC) can transfer relatively large loads. However, creep of the composite would cause the preload relaxation, resulting in reducing bearing capacity of the connection. To study the preload relaxation of PTTC caused by the creep of composites, a prediction formula is deduced by converting the viscoelastic problem to an elastic problem using Laplace transform. Meanwhile, long-term experimental research on the preload relaxation of composite pre-tightened tooth connection with different initial preloads and different geometry sizes was made. The theoretical results are compared with experimental data obtained by long-term experiment, and the results indicate that the calculation formula can predict the preload relaxation well in linear viscoelastic state. The preload relaxation mainly occurs at the beginning of loading and it tends to be steady in the middle and later periods.

Dough moulding compound (DMC) reinforced polymerized styrene butadiene rubber (SBR) / methyl vinyl silicone rubber (MVQ) composites were prepared, in which MVQ was matrix, DMC was a reinforcement phase and SBR was a compatibilizer. Dynamic thermomechanical analysis (DMA), infrared spectrum analysis (IR) and the effect of SBR and DMC content on mechanical properties, electrical insulating property and compatibility of the composites were investigated. The results showd that the morphology and thermal properties of the composites were improved when dough moulding compound was used as a reinforcement, and styrene butadiene rubber was compatibilizer, and had excellent insulating property with volume resistivity above 4.8×1012 Ω·m.

The AgSnO 2 NiO composites were prepared by internal oxidation method. The effects of different NiO content on the microstructure and mechanical properties of AgSnO 2 NiO composites were studied. The phase structure and surface morphology of the prepared AgSnO 2 NiO materials were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Metallographic Microscopy (MM). The results showed that the AgSnO 2 NiO composites with different NiO content can be obtained by the process of preoxidation of AgSn alloy powder and internal oxidation of ingot containing Ni. The agglomeration phenomenon of Ni in the silver matrix was serious, which led to the agglomeration of in-situ generated NiO particles after internal oxidation. After the multi-pass drawing, the SnO 2 particles dispersedly distributed in the AgSnO 2 NiO composites and the NiO particles gradually dispersed from the agglomerated state of the sintered ingot billet. The hardness of the prepared AgSnO 2 NiO composites increased slightly with the increase of NiO content. The mechanical properties test showed that the introduction of NiO particles significantly improved the tensile strength and elongation of AgSnO 2 materials to a certain degree. Adding proper amount of NiO is beneficial to improve the overall performance of AgSnO 2 materials.

This paper presents an experimental investigation of overall buckling behaviour of carbon fibre reinforced plastic (CFRP) tubes with different off-axis ply orientations. A series of specimens are designed and prepared with stacking sequences [0 ∘ 4 /± θ∘ ], with θ corresponding to either 0, 90, 45 or 60. Axial compression tests with effective end-reinforcement and hinge support are performed to investigate the overall buckling behaviour. With respect to the future design and application of CFRP tubes with this type of stacking sequence, column curves for each stacking sequences and all test data are fitted based on Perry-Robertson formula. With respect to the high stress level in the relatively short CFRP tube that facilitates the development of defects, test data present high levels of discreetness. We propose a strategy for engineering safe design in which a reduction factor is added to the original reduction factor based on statistical analysis when the universal slenderness ratio is less than 2.

The polymeric optical fibre technology can be successfully used for UV spectrum range radiation measurements.Anew type of fluorescent optical fibre optode is presented. The used fluorescent wave-shifter was used for UV-VIS conversion and radiation measurements. The linear characteristic with sensitivity 480 mW −1 is presented for UV range 7.2-13.6 mW. Presented optode construction advantages (small dimensions, low weight, high immunity to electromagnetic fields and distributed sensor architecture possibility) are attractive for numerous composite based engineering applications.

Ni and Cu are the two most promising alternatives to noble metals used in electrical conductive materials. However, Cu is susceptible to oxidation, while Ni exhibits poorer electrical conductivity. To solve this problem, Cu-Ni composite nanoparticles have been prepared in the present work by successive hydrazine reduction based on the different oxidation potential between Cu (II) and Ni (II). The as-prepared products were characterized by XRD, FE-SEM, EDS, and TG, and the electrical resistivity of which was measured by four-probe method. A formation process of the composite particles was proposed and demonstrated. The Cu-Ni composite nanoparticles have a uniform diameter of about 50nm, and exhibit higher oxidation temperature than Cu and lower electrical resistivity than Ni. This novel Ni-Cu structure and method might help solve the problems associated with the oxidation of Cu and the low electrical conductivity of Ni, which would further promote the application of base metal conductive powders.

In this work, hierarchical porous resins (PRs) are fabricated and applied as novel adsorbent for removal of oily substance. The oil/water (o/w) high internal phase emulsions (HIPEs), stabilized by phenolic resin precursor and tween 80, were used as the template for simultaneous polymerization of aqueous phase, methenamine, sodium persulfate and liquid paraffin. Subsequently, dopamine hydrochloride, 1-dodecanethiol and Fe 3 O 4 particles are grafted onto the interface of PRs via adhesion of dopamine and Markel addition reaction between quinone groups on dopamine and sulfhydryl groups on 1-dodecanethiol. The as-prepared composites possessed hydrophobicity and magnetic property (HPRs). The physical and chemical properties, morphology and adsorption properties of HPRs are characterized by XRD, FT-IR, TGA, SEM, N 2 adsorption-desorption isotherms. The as-synthesized HPRs composites had a typical hierarchical porous structure, and the resulted macropores with a well-defined open-cell and interconnecting pore throat structure could be controlled via the composition of the aqueous phase of emulsion. The hierarchical porous structure of HPRs contained macropores ranging from 0.3 μm to 4 μm and mesopores of 11.26 nm. HPRs have rough and hydrophobic surface (water contact angle of 130 ∘ ) with specific surface area of 15.06 m 2 /g and pore volume of 0.0349 cm 3 /g. The oil adsorption rate and the oil retention rate for toluene are 11.765 g/g and 86.43%, respectively. The oil adsorption rate in the first minute can reach more than 80% of the highest oil adsorption rate. The oil adsorption rate of HPRs after three recycling experiments can still reach 87.32%of the first-time oil adsorption rate.

In this study, cryogenic (77 K) to ambient (293 K) thermal shocks are induced to investigate the material behavior and failure characteristic of a random glass-mat-reinforced thermoplastic (GMT). The GMT has numerous advantages such as robust thermal conductivity, good mechanical strength, and good impact resistance. Hence, the GMT serves as an insulation material in liquefied natural gas (LNG) carrier-cargo containment systems (CCSs). In this study, 50, 100, 200, 400, and 800 cryogenic thermal cyclic shocks (77 K to 293 K) were applied to the fabricated GMT samples. The time for each cycle was 40 min, and it took up to approximately four months to completely apply the thermal cyclic shock to the specimens. The elongation, tensile strength, and elastic modulus of the testing samples obtained from the stress–strain relationship and morphologies were investigated in terms of the number of thermal cyclic shocks and strain rate. Finally, explicit formulae were proposed considering the parameters such as material properties and number of cryogenic thermal cycles to predict the material capabilities under arbitrary loading rates and cryogenic thermal cycles. It was confirmed that the degradation and defects increased with an increase in the number of cryogenic thermal cycles.

In the compounding of rubber composites, different non-black fillers are used to improve the physical properties, reduce the formulation cost, and provide special characteristics. Designing a rubber composite for a specific application needs the careful selection and differentiation of fillers based on its effect on processibility and overall material properties of the vulcanizate. However, fillers are usually classified according to their effect on reinforcement or function without much consideration to other properties such as vulcanization characteristics and heat aging resistance. Analyses of multiple properties are tedious when done in a univariate way. To differentiate non-black fillers with consideration to the various properties of rubber composites, linear discriminant analysis (LDA) of principal components (PCs) was used. This paper examines how vulcanization and mechanical properties can differentiate aluminosilicate, bentonite, and silica fillers in rubber composites. Aluminosilicate and silica were effectively differentiated frombentonite using the vulcanization characteristics and mechanical properties of rubber composites before heat aging. Better differentiation among the 3 non-black fillers was achieved when the mechanical properties of rubber composites after heat aging were included in the PC analysis. LDA required at least 6 PCs to correctly classify the non-black filler in 30 rubber composites.

The waste fly ash (FA) material was subjected to chemical treatment with HCl at elevated temperature for a different time to modify its porosity. Modified FA particles with highest surface area and pore volume were further used as a support for TiO 2 catalyst during FA/TiO 2 nanocomposite preparation. The nanocomposite photocatalysts were obtained by in situ sol–gel synthesis of titanium dioxide in the presence of FA particles. To perform accurate characterization of modified FA and FA/TiO 2 nanocomposite photocatalysts, gas adsorption-desorption analysis, X-ray diffraction, scanning electron microscopy, UV/Vis and Infrared spectroscopy were used. Efficiency evaluation of the synthesized FA/TiO 2 nanocomposites was performed by following the removal of Reactive Red 45 (RR45) azo dye during photocatalytic treatment under the UV-A irradiation. Photocatalysis has been carried out up to five cycles with the same catalysts to investigate their stability and the possible reuse. The FA/TiO 2 photocatalyst showed very good photocatalytic activity and stability even after the fifth cycles. The obtained results show that successfully modified waste fly ash can be used as very good TiO 2 support.

Chrysotile asbestos has excellent physical and chemical properties, but its high biotoxicity is very damaging to human health, due to its durability, high aspect ratio, and the exist of iron. By simple chemical treatment of chrysotile asbestos, silicon oxide nanofibers rich in hydroxyl groups on the surface can be prepared. In this study, we synthesized a series of polyurethane/silicon oxide nano-composite coatings with special performance following a blending method that introduced silicon oxide nanofibers into polyurethane. Measurement results revealed that, silicon oxide nanofibers can be used as reinforcing filler to increase the hardness, shear strength, wear resistance, thermal stability and chemical resistance of polyurethane coatings. And the optical performance test results indicate that the transmittance of the polyurethane coating decreased with increasing of silicon oxide nanofibers contents. However, the ultraviolet shielding effect of the polyurethane coating was improved to a certain extent with the addition of silicon oxide nanofibers.

Magnesium (Mg)-rich primer is considered as a substitute for high polluted chromate treatment technology to provide cathodic protection for aluminum (Al) alloy. In this paper, Mg-rich primer with comprehensive properties was prepared by modifying epoxy resin using direct mixing. Specifically, the influence factors on the dispersion of Mg powder in epoxy, the modification of epoxy resin using organic silicones and the performance of Mg-modified epoxy composite coating were studied. The results show that Mg powder with small particle size has a better dispersion in epoxy; The mechanical property such as flexibility and impact resistance decreases with the addition of Mg powder, but which was improved when using modified epoxy as the resin matrix due to introduction of Si-O-Si flexible chain; In addition, the grafting efficiency between hydroxyl terminated polydimethylsiloxane and epoxy resin was improved because of the introduced silane coupling agent like KH550 contains amino group; The electrochemical test results indicate Mg-rich primer could provide effective electrochemical protection for Al alloy by raising the corrosion potential and reducing the corrosion current density to bare substrate,respectively.

Polymers are widely used as replacements for machined metal components in engineering applications. To withstand extreme contact conditions, reinforcing materials are often introduced into polymers to improve their mechanical and wear properties. This paper investigates the applicability of basalt fibres as reinforcing materials to enhance the mechanical and wear properties of polyetheretherketone (PEEK). The weight percentage of short basalt fibres in PEEK composites was 0-10% based on the injection moulding method. The mechanical properties and tribological behaviours of the resulting composites were investigated. The results showed that the composites filled with basalt fibres exhibit significant improvements in strength, anti-indentation creep and hardness. Meanwhile, the friction coefficient and wear rate of the composites decreased obviously due to basalt fibres on the top of the worn surface bearing the dynamic load under sliding. The morphology of the worn surface indicates that fibre pull-out and fibre breakage both contribute to energy dissipation. However, the mechanical properties of the composites did not increase linearly with increasing fibre content because of the decreasing bonding force between the fibres and the matrix. These results are significant for the application of PEEK in engineering.

The present work refers to describe the effects of Al 2 Cu variations on various properties of thick-walled functionally graded (FG) cylindrical shell. Al-25 wt.% Cu hypo-eutectic alloy ingot is melted and centrifugally casted to obtain high entropy FG composite. A series of microstructure examinations such as FESEM and EDX analysis were carried out to determine the distributions of constituent phases and elements. It is revealed that the maximum volume fraction of Al 2 Cu particle is reached near the inner surface with 35.7 Vol .% and then reduces gradually to 32.5 Vol .% at the outer surface of FG cylindrical shell. The effects of the variations Al 2 Cu along radial direction of FG tube are discussed through Vickers hardness, wear rate, coefficient of thermal expansion and compressive test measurements. The experimental results show that the wear and hardness are varied in graded manner which the highest wear resistance with wear rate of 9.1×10 −5 g / mm 2 and hardness with 153HV are found towards Al 2 Cu enriched zone or inner periphery. Moreover, the studied FG cylindrical shell shows drop 2.5% in yield stress and 4.5% in elastic modulus from intermediate to inner layers due to Al 2 Cu particles clustering in metal matrix.

The wheel of a passenger vehicle must be designed to be safe and light. Despite the tremendous potential of carbon fibre as an automotive material due to high strength and low weight, the prevalence of carbon fibre reinforced plastics (CFRPs) in vehicle wheels is limited. Manufacturing and testing CFRP prototypes is expensive. Thus it is advantageous to develop simulation models for composite weight reduction. The simulation models can provide insight into how lighter CFRP wheels can be designed. This study presents the design development of a CFRP wheel for a high-performance roadster; the CFRP wheel is offered by an automotive manufacturer as a high-performance option instead of aluminium wheels. Finite element (FE) simulations were initially conducted assuming an isotropic material. This initial model was used to eliminate stress concentrations and to design and manufacture an initial CFRP wheel. The CFRP wheel weight is 6.8 kg as compared to the original aluminium wheel which weighs 8.1 kg. This initial design passed the dynamic cornering fatigue test (the most stringent strength test for wheels). Thereafter the wheel was instrumented with strain gauges and a bending moment was applied to the hub using a custom-built test rig. The test rig produced a static load equivalent to the dynamic cornering fatigue test (in which the applied bending moment varies sinusoidally). The test rig allowed for the deflection of the load arm to be measured. The comparison of the experimentally measured strains and an FE model which includes the CFRP laminate properties showed good agreement. Two alternative laminate options were simulated using the FE model. These showed both an increase in stiffness and a calculated weight reduction. This study shows that an aluminium wheel for a high-performance roadster can be redesigned using CFRP to be 16% lighter and using a FE model a further 152 g weight reduction is possible (18% weight reduction in total when compared to the aluminium wheel).

Polyaniline-poly vinyl alcohol (PANI-PVA) conducting blends containing 15 wt% aniline were synthesized by in situ polymerization of aniline. Three-phase polymer blended nanocomposites with different contents of magnetite (5, 10 and 15 wt.%) were also synthesized. We measured the current-voltage (I-V) curves for the conducting blend and its magnetite nanocomposite. We also measured their thermal stability, and performed kinetic analysis through thermogravimetric analysis. We observed that the three phase nanocomposites showed enhanced electrical conductivity compared with that of the conductive blend, and no electrical hysteresis. The PVA/PANi blend was more stable above 350 ∘ C and the addition of Fe 3 O 4 enhanced the thermal stability of the conductive blend. The apparent activation energy of the three phase nanocomposites was greater than those of both the pure PVA and PVA/PANi samples. These results suggest that such three phase nanocomposites could be used in a range of applications.

This paper studied the confinement effect of textile layers and the stirrup ratio on the seismic behaviour of TRC-strengthened RC columns using the numerical method. The results showed that the numerical values have good consistency with the experimental. Within the range of 1 to 3 layers of textile, with the increase of the number of textile layers, the peak load, displacement ductility ratio and energy dissipation capacity of the columns increased; however, these parameters only exhibited a limited increase when the textile layers continued to increase. In addition, the textile layers had a slight influence on the rate of the energy dissipation capacity. With the increase of the stirrup ratio, the yield load, peak load and ultimate load of the column did not change significantly, but the ductility coefficient and energy dissipation capacity of the column increased. Furthermore, for a TRC-strengthened column with three layers of textile and a stirrup ratio of 0.34%, the hysteresis loop fullness and the bearing capacity are better than those of a column with two layers of textile and a stirrup ratio of 0.67%. Therefore, it can be seen that TRC could play an efficient constraint role on the column when the stirrup arrangement is less.

The addition of polymers on asphalt binders aims to enhance their performance, especially at high temperatures, which correspond to rutting resistance. The Superpave rutting parameter (|G*|/sin δ ) has been considered to be inadequate to characterize the performance of modified materials, therefore the Multiple Stress Creep and Recovery (MSCR) test was developed, providing the parameter non-recoverable compliance (Jnr). This research has the main objective of correlating asphalt binders performance-based characterization with rutting resistance of asphalt mixtures, and presents results obtained for one conventional (50/70 penetration grade) and two modified asphalt binders (2.1% RET and 1.9% RET) regarding their rheological characteristics. With the use of the dynamic shear rheometer (DSR), master curves and MSCR results were obtained for the three binders. In addition, permanent deformation tests were performed on the asphalt mixtures by means of laboratory traffic simulation. The rutting characterization indicated higher permanent deformation resistance for the modified binders for the asphalt binder and the asphalt mixture testing. The main conclusions were that the use of modified binder reduced in approximately 50% the Jnr values and the rut depth; also, the asphalt binders’ characteristics were able to predict the asphalt mixtures rutting resistance.

The present work aims to research the treatment processing of magnesium reinforced with 1 μmsilicon carbide particle (SiCp) using stir casting combined by ultrasonic vibration. Present studies have been done on six different materials: (a) AZ31B alloy without particles, (b) 5 vol.% SiCp/AZ31B composites fabricated with different semi-solid stirring time (5 min, 10 min, 15 min and 20 min), (c) composite with 20 vol.% SiCp. The effects of 1 μm/SiCp pretreatment and stirring time on microstructure and interfacial wettability as well as mechanical properties of the materials were confirmed. Both short and long stirring time for the particle dispersion brought particle agglomeration. Results of SEM microstructure and tensile properties exhibited that the optimal stirring parameters of 625 °C/1500 rpm/15 min are exploited, and 20 vol.% SiCp/AZ31B composite was fabricated by the optimal stirring parameters. The application of optimal stirring parameters for the treatment resulted in homogeneous particle distribution. The addition of SiCp leads to a reduced matrix grain, and 20 vol.% SiCp/AZ31B composite showed smaller grain size than. 5 vol.% SiCp/AZ31B composite. The interface between SiCp and matrix is clear and interfacial wettability well. Tensile test results show that with increasing SiCp content, strengths increase while ductility decreases.

High cutting temperatures are easily generated during the machining of carbon fibre reinforced plastics (CFRP) and can induce serious damage during machining such as delamination. The purpose of this paper is to study the influence of cutting temperature on the performance of CFRP after machining. CFRP specimens were heated to temperatures within the vicinity of cutting temperatures generated during machining, then air-cooled and their bending properties investigated. The results showed that temperature had significant influence on the bending stress of CFRP. With increasing temperature, bending stress decreased and was lowest when the temperature was close to the glass-transition temperature. It was concluded that the bending properties of CFRP could be seriously affected if the material temperature was close to the glass-transition temperature and maintained for a period. As a result, cutting temperature should be kept lower than the glass transition temperature during machining.

BCN coatings with different chemical compositions were prepared using RF magnetron sputtering via adjusting N 2 flow. The influence of N 2 flow on the bonding structure, mechanical and tribological properties of coating was studied. The structural analysis indicated the coexistence of B-N, B-C, and N-C bonds, suggesting the formation of a ternary BCN hybridization. The maximum Vickers hardness of 1614.7 HV was obtained at the low N 2 flow (5 sccm), whereas the adhesion strength of BCN coatings on 316L stainless steel was improved with an increase of N 2 flow. The friction behavior of BCN coatings sliding against different materials (acerbic, beech and lauan wood) was performed using ball-on-disk tribo-meter in air. The low friction coefficient was easier to obtain as sliding against hardwood i.e. acerbic balls. BCN-5 and BCN-10 coatings presented better wear resistance regardless of softwood or hardwood, whilst other two coatings were more suitable for mating softwood i.e. beech and lauan.

This extensive study investigated the influence of microstructure on the effective transverse thermal conductivity of unidirectional glass fiber reinforced composites, in which the fibers are randomly dispersed and the thermal conductivity of polyethylene matrix is a function of test temperature. The microstructure is characterized by parameters such as the number of fibers, fiber volume fraction, fiber size, fiber arrangement and thermal property contrast. Firstly, a simple algorithm is developed to automatically generate closest-to-real random array of fibers in unit cell to reconstruct the composite microstructure. Then, the established two-dimensional random two-component composite unit cell is solved using finite element simulation and the obtained effective thermal conductivities are compared with the theoretical predictions and the experimental results. Subsequently, the effects of microstructure parameters and test temperature are investigated, respectively. It is found that the finite element predicted properties are in very good agreement with the experimental predictions, while they are always lower than the analytically predicted properties. These results can find applications in the design of composite materials taking into account the fiber distribution morphology.

Chicken eggshell (Es) waste is an industrial byproduct, and its disposal constitutes a severe environmental risk. Eggshell is a new engineering reinforcement retaining excellent properties such as low density, renewable, eco-friendly, and high thermal stability. The current research aims to study the effects of eggshell particles addition on microstructures, mechanical and tribological properties of aluminium/eggshell green metal matrix composites (MMCs). In the present work Al–Es metal matrix composite is produced by powder metallurgy processes. SEM with EDX and XRD were used to examine the microstructures and the compounds that arise during the sintering process of the produced composites. Six tests were conducted on the produced samples including; dry wear test, micro Vickers hardness, and ultimate compressive strength. The results showed that the addition of 3 wt. % of eggshell improved wear resistance (65%), compressive strength (40%) and hardness (15%). At 6 and 9 wt. % of eggshell, negative results appeared.

The flexural analysis of doubly curved functionally graded porous conoids was performed in the present paper. The porosities inside functionally graded materials (FGMs) can occur during the fabrication and lead to the occurrence of micro-voids in the materials. The mathematical model includes expansion of Taylor’s series up to the third degree in thickness coordinate and normal curvatures in in-plane displacement fields. Since there is a parabolic variation in transverse shear strain deformation across the thickness coordinate, the shear correction factor is not necessary. The condition of zero-transverse shear strain at upper and lower surface of conoidal shell is implemented in the present model. The improvement in the 2D mathematical model enables to solve problems of moderately thick FGM porous conoids. The distinguishing feature of the present shell from the other shells is that maximum transverse deflection does not occur at its centre. The improved mathematical model was implemented in finite element code written in FORTRAN. The obtained numerical results were compared with the results available in the literature. Once validated, the current model was employed to study the effect of porosity, boundary condition, volume fraction index, loading pattern and others geometric parameters.

One of the advantages of cement and the cement concrete industry in sustainability is the ability to utilize large amounts of industrial solid wastes such as fly ash and ground granulated blast furnace slag. Tailings are solid wastes of the ore beneficiation process in the extractive industry and are available in huge amounts in some countries. This paper reviews the potential utilization of tailings as a replacement for fine aggregates, as supplementary cementitious materials (SCMs) in mortar or concrete, and in the production of cement clinker. It was shown in previous research that while tailings had been used as a replacement for both fine aggregate and cement, the workability of mortar or concrete reduced. Also, at a constant water to cement ratio, the compressive strength of concrete increased with the tailings as fine aggregate. However, the compressive strength of concrete decreased as the replacement content of the tailings as SCMs increased, even whentailings were ground into smaller particles. Not much research has been dedicated to the durability of concrete with tailings, but it is beneficial for heavy metals in tailings to stabilize/solidify in concrete. The clinker can be produced by using the tailings, even if the tailings have a low SiO2 content. As a result, the utilization of tailings in cement and concrete will be good for the environment both in the solid waste processing and virgin materials using in the construction industry.

The analytical model applicable to calculate the equivalent stiffnesses of composite box beam has been refined. The calculation of equivalent stiffness coefficients of composite laminated box beam is simplified and the connection between shear-deformable beam theory and classical laminate theory is established. The equivalent stiffness analytic formulas expressed by beam cross-section geometry and laminate stiffness coefficients are obtained. These analytical formulas are suitable for composite laminated box beam with circumferential uniform stiffness, and accounts for bending- transverse shear and torsiontensile coupling effect. The correctness and precision of refined analytical model is verified by test and finite element method, respectively. The influences of the lay-ups on the elastic coupling of composite structures and their causes are studied. The variation of the equivalent stiffnesses of the laminated box beams with different lay-ups is predicted. The global buckling analysis of composite laminated box beam considering the transverse shear deformation is carried out. The formula of the global buckling critical load is obtained combining with the theoretical formulas of equivalent stiffnesses. The influences of the lay-ups, shear deformation and slenderness ratio on the global buckling critical load are studied.

This work investigates the limit of Cd doping in ZnO derived by means of mechanochemical synthesis using CdCl 2 , ZnCl 2 and Na 2 CO 3 as precursors and NaCl as diluent. The prepared samples were characterized using X-ray diffraction (XRD), Fourier transformed infrared attenuated total reflectance (FTIR ATR) spectroscopy, UV-Vis diffuse reflectance spectroscopy (DRS),N 2 adsorption-desorption isotherms, scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS), while photocatalytic efficiency has been evaluated for methylene blue degradation process. Zn for Cd replacement limits in the crystal lattice of ZnO derived via mechanochemical synthesis were found to be only 2%. For Cd present in a larger portion, CdO and CdCO 3 phases appear. Cd doping limits in ZnO were not affected by the milling interval. However, it was observed that Cd doping impairs the nanocrystallinity of ZnO. The morphology and the electronic structure of ZnO and thus photocatalytic activity was inappreciably affected by the Cd doping.

This paper studies the free vibration of polymer nanocomposite reinforced by graphene sheet. In this work, the new size dependent formulation is presented for nanocomposites based on couple stress theory. For this purpose, the first shear deformation theory is applied. The effect of scale parameter is investigated based on anisotropic couple stress theory. Vibration equations of the composite lamina are extracted using Hamilton’s principle. Numerical results are provided for Poly methyl methacrylate/graphene composite.Mechanical properties of the composite are obtained from molecular dynamics simulation. Based on eigenvalue procedure, an analytical solution is obtained for the natural frequency of composite lamina. In the results section, the effect of dimensional and physical parameters are investigated on lamina natural frequency. It is observed that graphene defects caused to diminish the lamina frequency. Furthermore, it is revealed that the increase in graphene volume fraction leads to natural frequency be greater.

The use of fiber-metal laminates (FML) allows for substantial advantages over a fuselage skin made of monolithic aluminum materials. Glass fiber prepreg reinforced aluminium is characterized by high damage tolerance capabilities, supporting the structural strength capability in case of any kind of damage. For this reason, FML, and GLARE in particular, have been identified as superior materials for aerospace applications. More than 400m 2 FML is applied on each A380, as skin panels and as D-noses for both, vertical and horizontal stabilizer. FML possess the potential to become the baseline material for next-generation single-aisle aircrafts [1, 2, 6]. The development of a new production chain that will allow automated fuselage production for future short-haul aircrafts is the focus of the studies that make up the joint project AUTOGLARE. As part of the fifth call-up for the German Aeronautical Research Programme (LuFo), the German Aerospace Center (DLR) is working with its project partners Airbus Operations, Premium Aerotech (PAG) and the Fraunhofer Gesellschaft (FhG). The development of a production chain for stiffened fuselage panels made of Fiber metal Laminates should support a production rate of 60 aircraft per month [3]. This study contains the research work of the DLR and FhG regarding the automated and quality assured process for chain stiffened FML fuselages. In addition to a detailed explanation of the systems that were set up, this paper covers the planned tests, the completed demonstration models and the findings derived from them.

This paper aimed to investigate the stitching effect on the bond strength of single lap shear joints in carbon/epoxy composite laminates using experimental and simulation methods. Stitched and unstitched single lap shear joints were bonded using the EC-3448 epoxy adhesive and tested under different working environments, including room temperature/dry (RTD), elevated temperature/wet (ETW) and cold temperature/dry (CTD). The results showed that stitching improved the bond strength of the stitched single lap joints, with approximately 60% higher strength for stitched compared to unstitched lap joints under RTD and CTD environments and 10% higher strength under an ETW environment. The increase was smaller under ETW conditions because the adhesive recured under elevated temperature. Embedded interactions connected the lapping plates and the stitch line, and the maximum stress failure criterion was adopted for the stitch line. As the predicted failure modes are consistent with the experimental results, the progressive damage mode can be applied to simulate stitched composite structures.

Due to the properties of shape memory effect and super-elasticity, shape memory alloy (SMA) is added into glass fiber reinforced polymer (GFRP) face-sheets of foam core sandwich panels to improve the impact resistence performance by many researchers. This paper tries to discuss the failure mechanism of sandwich panels with GF/ epoxy face-sheets embedded with SMA wires and conventional 304 SS wire nets under low-velocity impact and compression after impact (CAI) tests. The histories of contact force, absorbed energy and deflection during the impact process are obtained by experiment. Besides, the failure modes of sandwich panels with different ply modes are compared by visual inspection and scanning electron microscopy (SEM). CAI tests are conducted with the help of digital image correlation (DIC) technology. Based on the results, the sandwich panels embedded with SMA wires can absorb more impact energy, and show relatively excellent CAI performance. This is because the SMA wires can absorb and transmit the energy to the outer region of GFRP face-sheet due to the super-elasticity-behavior. The failure process and mechanism of the CAI test is also discussed.

In this study, the electromagnetic interference (EMI) shielding effectiveness (SE) of polymer composites based on natural graphite in flakes (NGF) and silicone rubber was investigated with the aim to contribute to the development of the technology of electromagnetic shielding materials. This topic has attracted great attention to the aeronautical and aerospace applications, due to the serious problems that EMI can cause to the functioning of electronic devices. According to this, the present work has produced samples of composite materials with variations on the sizes of the filler particles and composition of the samples. The electromagnetic characterization of the samples is given by the Vector Network Analyzer (VNA) in the X-band frequency range (8.2 – 12.4 GHz). The results indicate that the variation of particle sizes is determinant to the SE performance along with the X-band frequency range. Furthermore, the expansion of the range of granulometry allows controlling the curves of the peaks along the X-band.

The traditional craft of marine launching rubber gasbag that made by hand laying cord fabric has the disadvantages of irregular reinforcing direction and discontinuity of cord, which leads to the limitation of bearing capacity of gasbag and poor reliability. Based on the analysis of the structure of the rubber gasbag and geodesic winding pattern used in marine launching, the winding process design and experiment of the fiber reinforced rubber gasbag are carried out to solve the problem. The numerical simulation of the wound rubber gasbag is established by the finite element software ABAQUS in order to study the geometrical and contact nonlinearity of the gasbag, and the nonlinear relationship of parameters in application process, and then compare the application performance with those of the traditional cord fabric placement molding. Finally, the winding pattern test and deformation simulation experiment are carried out to verify the fact that the reinforced rubber gasbag with glass fiber / polyurethane composite material has a higher bearing capacity compared with the traditional handmade rubber gasbag. Thus, it provides theoretical and experimental evidence for the winding process of rubber gasbag.

Aiming at the problem of poor processing performance and difficult processing in the process of aluminum-based diamond composites for electronic packaging, this paper uses electrolytic in-process dressing (ELID) grinding technology to grind the aluminum-based diamond composites. The quadratic orthogonal rotation combination method was used to investigate the influence law and degree of grinding depth, grinding wheel linear velocity, duty cycle and electrolysis current on surface roughness. The ELID grinding optimization process parameters of aluminum-based diamond composites obtained by LINGO software are: grinding depth 9.3μm, grinding wheel linear speed 36m/s, duty cycle 63.7%, electrolysis current 11.5A. The surface of the aluminum-based diamond composite with a surface roughness of 125 nm was machined by this optimized process parameter combination.