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Epoxy-polyamide CNTs reinforced nanocomposites have the excessive ability for their uniform structures and specific properties and have considerable attention owing to their potential applications. In this work, epoxy/polyamide (ER-PA) and CNTs reinforced epoxy/polyamide (ER-PA/CNTs) nanocomposites were prepared by using the solution casting method. Herein, Fourier transforms infrared spectroscopy (FT-IR) was applied to indicate the responsible functional groups, presented in the prepared nanocomposites. Surface morphology and particle dispersion of the prepared nanocomposites were examined by scanning electron microscopy (SEM). The obtained results demonstrated that the CNT's weight content, dispersion rates, and the surface functionalization of CNTs nanoparticles have a strong influence on the surface morphology of the prepared nanocomposites. The thermal properties and crystalline nature of the ER-PA/CNTs nanocomposites were studied by using thermogravimetric analysis (TGA) and X-ray diffraction (XRD) analyses. The prepared nanocomposites showed good thermal stability and crystalline behavior as compared to the ER-PA nanocomposites network system. From the obtained results, it can be assumed that this effort can help to design other reinforced nanocomposites for promising applications in the nanocomposites materials industry. [ABSTRACT FROM AUTHOR]

Incorporating distiller's grains (DG) into poly(ethylene terephthalate) (PET) has not been investigated because DG is not suitable for processing at high temperatures. Hence, in this study, DG was treated with methylenediphenyl diisocyanate (MDI) to prepare reinforced DG (RDG), which was then used as a biological filler that was melt-mixed with a PET resin to produce PET/DG and PET/RDG composites. The composite mechanical properties were investigated. Compared with PET/DG composites, PET/RDG composites exhibited improved mechanical properties. When the RDG content was 12.5%, the elongation at break reached the maximum. Scanning electron microscopy was used to observe the structure of composites filled with MDI-modified DG at the tensile section, and the compatibility between RDG fillers and the PET matrix was analyzed; RDG dispersed and adhered well in the matrix. The FTIR results showed the appearance of new characteristic peaks, indicating the possibility of DG reacting with MDI after the blending with PET, as well as providing clues about the probable reaction mechanism. Through X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, and water absorption tests, the crystallinity, thermal stability, and water absorption for the composites were analyzed. The results of TGA showed that RDG had a higher thermal stability than DG. Adding DG could significantly increase the crystallinity and rate of crystallization of PET, and at the same time, it could also improve the water absorption performance of the composites. But in the case of DG modification or treatment with MDI, the water absorption was slightly reduced. The results of contact angle analysis showed that the surface of PET/RDG composites had higher hydrophobicity than that of PET/DG composites because of the tighter structure. Relative to DG, RDG also effected improvement in the thermal stability of PET. [ABSTRACT FROM AUTHOR]

Plant fibers are one of the most promising calcium silicate board (CSB) reinforcement materials because of their many sources, suitable sizes, high tensile strengths, and natural renewable properties. In this study, an applicable plant fiber selection method for reinforcing CSBs was established. The morphology, components, and mechanical properties of different brands of plant fibers were analyzed for factor screening. Based on the wet processes of CSBs, the effects of plant fiber additions on the mechanical properties of CSBs were studied, and the optimum addition amount of plant fiber was determined to be 8 wt.%. Through multiple linear regression analysis of the physical and chemical properties of plant fibers and the mechanical properties of CSBs, a plant fiber strengthening index (Fsi) and toughening index (Fti) of CSBs were formulated as a plant fiber applicability index. The fitted R2 values of the plant fiber strengthening index and toughening index were 0.88 and 0.71, respectively, showing good correlation. The validity of the plant fiber applicability index in evaluating the fiber reinforcement potential was verified by experiments. The results provided a significant method for the prediction of plant fibers' reinforcement potential and the selection of plant fibers for CSB reinforcement. [ABSTRACT FROM AUTHOR]

Soil–reinforcement interaction is a major factor in the analysis and design of reinforced earth structures. In current research the effects of attaching elements of different size and numbers as anchors on enhancement of interaction at soil–geogrid interface under direct shear conditions were studied. Poorly and well graded sands (SC & Sf), a high density polyethylene geogrid, anchors with three different size and numbers (layouts) and clamping length of 2 cm from shear surface were used. Samples were prepared dry at a relative density of 80% in a 30 × 30 cm direct shear box and subjected to normal pressures of 12.5, 25 and 50 kPa with the shear load applied at a rate of 1 mm/min. Results of the assessment show that anchored geogrids improve shear resistance at interface mainly due to mobilization of passive soil resistance that is significantly influenced by the magnitude of the normal pressure and the number and size of anchors. Interaction enhancements achieved varied between a minimum of 8% and a maximum of 42%. [ABSTRACT FROM AUTHOR]

Application of plant fibers in calcium silicate boards is in line with developmental trends favouring green building materials, but the bonds between them still need to be strengthened. To improve the combination of fibers and the inorganic matrix, the effects of softwood pulp fibers with different beating methods and beating degrees on the properties of calcium silicate boards were studied. The results showed that medium and high consistency beating maintained the lengths of the fibers and were suitable choices. The fine fibers on the surfaces of the fiber were anchored inside the matrix after beating, which increased bonding between the fibers and the matrix. The optimum beating degree was 45 ° SR, and the flexural strength and fracture toughness of the calcium silicate board were 26.13 MPa and 2.68 KJ/m2, respectively, 50% and 160% higher than those seen for 8 ° SR (without beating). [ABSTRACT FROM AUTHOR]

The use of natural fiber in cementitious materials can contribute to the improvement of technological properties and environmental issues related to the reuse of agro-industrial waste. World pineapple production is approximately 12.8 million tons per year, generating large environmental impacts, because the disposal natural fibers in landfills. The objective of this research was to evaluate the potential of reusing the natural fiber from the pineapple crown as a reinforcement element in eco-friendly mortar for the purpose of recovering building structures committed to coastal environments, evaluating the influence of the fiber surface treatment process with NaOH and its durability in laboratory conditions, in addition to avoiding the disposal of this waste in landfills. The natural fibers were characterized physically, morphologically and chemically, in the treated and untreated (natural) condition, for further technological evaluation of mortars in the fresh state, such as consistency, specific mass, incorporated air and water retention. Comprehensive studies of the hardened state were also carried out to study mechanical strength (compressive, flexural and tensile), water absorption due to capillarity and immersion, as well as durability by evaluating mass loss and mechanical strength after exposure conditions. The results showed that the fiber treatment process improved its characteristics for application in mortar with addition of 2.5% fiber treated in cement mass, causing the better in the technological and durability properties, and a proposed new means of disposing of agro-industrial waste, contributing to a circular economy. [ABSTRACT FROM AUTHOR]

Propagation behavior of SH-wave in a layered structure comprises of a functionally (exponentially) graded fibre-reinforced substrate imperfectly bonded to a functionally (exponentially) graded Voigt-type viscoelastic stratum is studied. The complex form of frequency equation is achieved in closed-form whose real part represents dispersion relation and imaginary part represents damping equation. In isotropic case, dispersion relation coincides with classical Love- wave equation whereas damping equation vanishes identically for the classical case. The effects of imperfect bonding, wave number, functional gradient parameters of stratum and substrate, viscoelasticity in stratum and reinforcement in the substrate are analyzed on the phase as well as damped velocities of SH-wave. Furthermore, the impact of imperfect common interface on the propagation of SH-wave is examined meticulously by analyzing the effect of flexibility and viscoelastic component associated to the imperfect bonding of stratum and substrate. Numerical calculations and graphical demonstrations are carried out for the present study which unravels some important peculiarities. [ABSTRACT FROM AUTHOR]

A novel type of poly(2-methoxyaniline)@carbon black (P2MA@CB) was formulated by incorporating laboratory synthesized CB nanoparticles into pure P2MA. The resulting materials were characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and electrochemically by cyclic voltammetry (CV). The optical study shows the P2MA@CB samples to be of nanosize. Besides, the CV results show that this nanomaterials exhibited high electroactivity. All the results demonstrated that the P2MA@CB (0.5g) hybrid material is very promising for application in electrochemical sensing. [ABSTRACT FROM AUTHOR]

The present study reports the findings about developing the energy storage resources following a green and economically viable method. Polythiophene (PTh) and its nanocomposites (PTh/CdSe) were synthesized using a chemical oxidative polymerization method. The FTIR spectra of the as-prepared composite confirm the presence of CdSe in PTh matrix. The XRD spectra suggest for the amorphous nature of native PTh which further changes into semicrystalline nature when CdSe was incorporated into it. PTh/CdSe nanocomposites showed both cubic and hexagonal phases, and the crystallite size was found to increase from 8 nm to 45 nm when CdSe was reinforced into the PTh matrix. Transmission electron microscopic images of pure PTh showed spherical morphology of the particles joined to each other through van der Waals forces. The doping of CdSe also results in appearance of needle-like nanostructures over PTh surfaces. These isolated needles have CdSe nanorod-like structures. Impedance data reveal that charge transfer resistance (Rct) of pure PTh is higher than that of the PTh/CdSe nanocomposites. The reduced charge transfer resistance (Rct) indicates that conductivity of nanocomposites is higher than that of the native one. When PTh was reinforced with the CdSe, they showed an increase in dielectric constant which is due to the alignment of polarization charges with increased frequency. This mechanism of polarization is helpful in increasing the charge storage capacity of the material. Thus, the observed results may open up doors of new avenues to design energy storage devices using conducting polymer/semiconductor nanocomposites. [ABSTRACT FROM AUTHOR]

In this study, a polymer blend consisting of thermoplastic polyurethane and polycaprolactone, which was used as the self-healing matrix, was prepared via a solution casting method. Cellulose nanocrystals (CNCs) were then incorporated to enhance the interfacial compatibility of the multi-material and maintain its self-healing ability via the three-dimension printing method. The effects of the CNCs on the chemical structure, mechanical, and thermal properties of the polymer composites were investigated. The results show that the composites with CNCs exhibit excellent tensile and thermal properties, and a high interfacial compatibility. Specifically, the blend containing 1% of CNCs possesses excellent mechanical properties, as its tensile strength of 31 MPa and elongation at break of 1600% show. Further analyses on the reinforced mechanism of such mixture were carried out by using molecular dynamics simulations. The CNC-reinforced composites maintain their good self-healing properties and function for a minimum of three cycles. Their superior thermal stability, mechanical, and self-healing properties, as well as the low cost of the raw materials, and the simple manufacturing process make these blends ideal for surface protection coatings, sensors, and healthcare materials applications. [ABSTRACT FROM AUTHOR]

In this study, vibration and dynamic stability of fluid-conveying thin-walled rotating pipes reinforced with functionally graded carbon nanotubes are studied. The pipe is modeled based on thin-walled Timoshenko beam theory and reinforced by single-walled carbon nanotubes with uniform distribution as well as three types of functionally graded distribution patterns. The governing equations of motion and the associated boundary conditions are derived via Hamilton’s principle. The governing equations of motion are discretized via the Galerkin method, and the eigenfrequency and the stability region of the pipe are found using the eigenvalue analysis. Some numerical examples are presented to study the effects of length-radius ratio, carbon nanotubes distribution, volume fraction of carbon nanotubes, rotational speed and mass ratio on the non-dimensional eigenfrequency and critical flutter velocity of the thin-walled rotating pipe conveying fluid. The results show that the carbon nanotubes distribution has a significant effect on the non-dimensional eigenfrequency and critical flutter velocity. Also, it is found that the rotational speed has a stabilizing effect on the dynamic behavior of the system. [ABSTRACT FROM AUTHOR]

Extensive laboratory model tests have been carried out on a strip footing resting over dry sand bed subjected to eccentrically inclined load to determine the ultimate bearing capacity (Patra et al. in Int J Geotech Eng 6(3):343-352, 2012a. 10.3328/IJGE.2012.06.03.343-352, Int J Geotech Eng 6(4):507-514, b. 10.3328/IJGE.2012.06.04.507-514). Similarly, lower bound calculations based on finite element method were performed to compute the bearing capacity of a strip footing subjected to an eccentric and inclined load lying over a cohesionless soil with varying embedment depth and relative density (Krabbenhoft et al. in Int J Geomech ASCE, 2014. 10.1061/(ASCE)GM.1943-5622.0000332). The load may be applied in two ways namely, towards the center line and away from the center line of the footing. Based on the results (both experimental and numerical analyses), a neural network model is developed to predict the reduction factor that will be used in computing the ultimate bearing capacity of an eccentrically inclined loaded strip footing. This reduction factor (RF) is the ratio of the ultimate bearing capacity of the footing subjected to an eccentrically inclined load to the ultimate bearing capacity of the footing subjected to a centric vertical load. A thorough sensitivity analysis is carried out to evaluate the parameters affecting the reduction factor. Based on the weights of the developed neural network model, a neural interpretation diagram is developed to find out whether the input parameters have direct or inverse effect on the output. A prediction model equation is framed with the trained weights of the neural network as the model parameters. The predictions from ANN, and those from other approaches, are compared with the results computed from both experimentation and FEM analyses. The ANN model results are found to be more accurate and well matched with other results. [ABSTRACT FROM AUTHOR]

Geosynthetic-reinforced retaining (GRR) walls have been increasingly used to support roadways and bridge abutments in highway projects. In recent years, advances have been made in construction and design of GRR walls for highway applications. For example, piles have been installed inside GRR walls to support bridge abutments and sound barrier walls. Geosynthetic layers at closer spacing are used in GRR walls to form a composite mass to support an integrated bridge system. This system is referred to as a geosynthetic-reinforced soil (GRS)-integrated bridge systems (IBS) or GRS-IBS. In addition, short geosynthetic layers have been used as secondary reinforcement in a GRR wall to form a hybrid GRR wall (HGRR wall) and reduce tension in primary reinforcement and facing deflections. These new technologies have improved performance of GRR walls and created more economic solutions; however, they have also created more complicated problems for analysis and design. This paper reviews recent studies on these new GRR wall systems, summarizes key results and findings including but not limited to vertical and lateral earth pressures, wall facing deflections, and strains in geosynthetic layers, discusses design aspects, and presents field applications for these new GRR wall systems. [ABSTRACT FROM AUTHOR]

The influence of polypropylene (PP) fibers on thermal behavior of concrete at elevated temperatures was studied by simultaneous thermal analysis. Two kinds of polypropylene fibers differing in form and size were applied as fillers. Special emphasis was given on the thermal behavior of PP fiber-reinforced concrete subjected to heat treatment, i.e., at 200 and 300 °C. Thermal events of concrete samples with and without fibers were characterized. In comparison to concrete sample without fibers, the results showed that the presence of polypropylene fibers affected the thermal stability of concrete samples. It was found that the influence of the kind and the amount (1.8 vs. 3.0 kg m−3) of PP fiber on the thermal stability of concrete samples was not significantly pronounced. [ABSTRACT FROM AUTHOR]

The chitosan-microparticles reinforced cellulose biocomposite sponges regenerated from ionic liquid were prepared and characterized. Fourier transform infrared (FTIR) spectroscopy confirmed that the cellulose dissolved in 1-allyl-3-methylimidazolium chloride without derivatization. Chitosan particles as reinforcement were incorporated into the cellulose matrix. FTIR spectra indicated hydrogen bonding between hydroxyl groups of cellulose and chitosan. The biocomposite sponges showed uniform three-dimensional interconnected porous structures. The breaking strength of the sponges increased significantly, from 0.09 to 0.32 MPa with the addition of 1.0 wt% chitosan. The sponges also demonstrated excellent antibacterial activity against S. aureus and E. coli with the average inhibition zone diameters >2 mm and the inhibition rate higher than 80 %. Furthermore, the biocomposite sponges exhibited good moisture penetrability and high porosity. The water uptake ability of the sponge was >25 times of its weight in water with a fast swelling. The chitosan/cellulose composite sponge is expected to be a promising material for potential applications as wound dressing. [ABSTRACT FROM AUTHOR]

During severe wind storms or strong ground motions, so many constructed reinforced concrete (RC) minarets are severely damaged or collapse causing the loss of lives and economy. Damages or collapses of RC minarets after these miserable acts of nature compel us to revise our knowledge about the structural wind and earthquake analyses of these structures. The main objectives of this study are to make structural wind and earthquake analyses of representative RC minaret, to compare and discuss the results of the analyses and to clarify the weaknesses of these structures. The findings of this study showed that the analyses results found from earthquake time history analysis should be used in the structural design of RC minarets and that extra care should be taken in those places where there is a decrease in cross section and door opening occurs. [ABSTRACT FROM AUTHOR]

In this paper, equations are derived to calculate the factor of safety, in addition to the force required for reinforcement to achieve the desired factor of safety in reinforced embankments. The equations are derived based on the limit equilibrium approach. Assuming the failure surface to be an arc of a circle, solutions have been developed to take into account the effect of applied loads and the effect of applying the reinforcement in layers. For the equations derived to give valid solutions, assumptions should be satisfied. These include: the center of the slip circle must lie at a level at or above the bottom of the tension crack; the entire berm should lie within the failure plane; and the direction of reinforcement force is assumed to be horizontal. Typical examples have been analyzed to illustrate the use of the solutions. A comparison is made with the results of Bishop's simplified method of slices through the software PROKON and previous analytic solutions, and good agreement was obtained. [ABSTRACT FROM AUTHOR]

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This paper presents the structural behaviour of reinforced concrete (RC) beams with and without openings strengthened externally with bamboo fiber reinforced composite (BFRC) plates in shear and flexure, respectively. Mechanical properties include tensile and flexural strength of epoxy, polyester and vinyl-ester based BFRC plates with 0%, 10%, 20%, 30% and 40% fiber volume fractions were evaluated. A total of fourteen beams were cast to evaluate the structural behaviour of RC beams strengthened with BFRC plates. All the beams were tested to failure under four-point bending. The results presented were in terms of load–deflection behaviour, failure mode and crack pattern. A comparison was also made between the performance of epoxy, polyester and vinyl-ester based BFRC plates in shear strengthening of RC beams with openings. Results revealed that the presence of openings in the shear zone reduced the original beam capacity of the control beam to about 52–55%. Shear strengthening of RC beams with openings using epoxy based BFRC plates showed significant improvement in regaining the beam structural capacity to approximately 32–36% higher than the un-strengthened beams. Meanwhile, strengthening of RC beams in flexure with epoxy based BFRC plates managed to regain the beam original capacity up to 98% of the control beam. Bamboo fiber composite reinforced with epoxy, polyester and vinyl-ester resins of 40% fiber volume fraction managed to regain the beam original capacity up to 82%. It was found that BFRC plates could divert and mitigate the formation of cracks away from the strengthened region as well as improved the beam ductility. [ABSTRACT FROM AUTHOR]

The article handles potential approaches to design and determination of total load capacity of foundation slabs and floors. The research is focused on punching shear failure of reinforced ground supported slab. The article presents detailed results of the experiment made and advanced numerical modelling based on nonlinear analysis and application of fracture-plastic model. The experiment made included a 2.0 × 1.95 m reinforced concrete slab-on-ground of 120 mm thickness. The experiment was followed by a parametric study of total load capacity calculation with nonlinear analysis which is supplemented by calculations based on existing design model code. [ABSTRACT FROM AUTHOR]