نشریه علوم و فناوری کامپوزیت
سال چهارم شماره 3 (پیاپی 13، پاییز 1396)

In this study, a novel method was used to increase alumina nanoparticles content in nickel base composite coatings plated by pulse current. Methanol, ethanol and formaldehyde were partially added to the Watt’s solution as organic substances and nickel alumina nanocomposite coatings were produced adopted by simultaneous ultrasonic and magnetic homogenizing. After electroplating, the effect of these organic solvents was investigated by comparison of cross sectional observation of the coatings by field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray analysis (EDX). The hardness and wear behavior of electroplated nanocomposite coatings were evaluated by ball on disk test at room temperature and ambient air. Microstructures studies showed that the amount of incorporated nanoparticles in the coatings plated with the electrolyte without organic solvent is 2.1 wt. % and this amount increases with the addition of organic solvents. So that, the maximum amount of nanoparticles in this study (5.2 wt. %) is achieved by adding methanol. Surface hardness of the coatings plated with Watt’s solution was 301 Hv which increased to 485 Hv with adding methanol. Wear tests also showed that the addition of methanol increased the wear resistance twice more than the electrolyte without organic solvent. The microhardness investigation verifies this fact that increasing of reinforcement nanoparticles and coating’s microhardness due to adding methanol provides the oxide layer’s mechanical strength and creates the highest wear resistance in the plated nanocomposites.

Ordered Fe100−x Mn x (0 ≤ x ≤ 87) nanowire arrays have been prepared by co-electrodeposition of Fe and Mn into pores of homemade anodized aluminum oxide (AAO). The influence of composition, annealing temperature, and frequency on structure and magnetic properties of Fe/Mn nanowires was studied. The changes in the saturation magnetization, coercivity (Hc), remanent squareness (Mr/Ms), and crystal structure of nanowires with changing of the above parameters were also investigated. The results of XRD and SEM suggest that the nanowires have a bcc structure and that their phases change with the annealing temperature. The nanowires have uniaxial magnetic anisotropy with easy magnetization direction along the nanowire axis due to the large shape anisotropy. Also, the coercivity of the Fe100−xMn x nanowires was increased with increasing annealing temperature for all the compositions. On the other hand, the nanowire arrays electrodeposited at different electrodeposition frequencies show remarkably different magnetic behaviors, due to increasing of the electrodeposition frequency, the rate of ions for reduction was decreased.

Composite materials such as fiber reinforced polymeric laminates are used extensively in various engineering applications. Of the greatest impediments to the use of these materials in advanced applications is the reduction of their mechanical properties and structural integrity when they are exposed to high temperatures. In this paper, the effect of nanoclay addition on impact properties of composite and fiber metal laminates before and after exposure to high temperature shock have been investigated. For this purpose, the nanoclay particles were added to pure epoxy resin using mechanical mixer, high-speed mechanical homogenizer, and ultrasonic homogenizer. Then, both the composite laminates and fiber metal laminates 2/1 were laminated by aluminum sheets, pure epoxy resin and modified resin with nanoclay and glass fiber using hand lay-up process. The effects of using nanoclay on the impact strength of composite laminates and fiber metal laminates before and after exposure to temperature of 230 ° C were studied. According to the results obtained, it was found that nanoclay has effective role in maintaining impact properties of the specimens. Additionally, as a result of protective role of metallic layers, the thermal shock induced degradation in impact properties of fiber metal laminates was decreased.

Metalic composite tubes, used in special applications such as aerospace and oil industries, can be produced by multi-layered tube hydroforming. Pressure and feed loading paths are two important parameters in two-layered tube hydroforming process. Theoretical formulas don’t exist to obtain correct pressure and feed loading paths. On the other hand, these loading paths have a significant influence on the quality of products. Therefor determining of optimal pressure and feed loading paths with meta-heuristic algorithm was studied in this paper. First, finite element (FE) model of two-layered tube hydroforming process was created and validated with experimental data. Then FE model and meta-heuristic optimization algorithm were combined to determine of the loading paths. In this paper, genetic algorithm was used as a meta-heuristic optimization. Conformation of the geometrical dimension of the product with the design dimension of final product was goal function in this algorithm. Also, the maximum amount of thickness changing and Von-mises stress were considered as constrains of optimization. Both loading paths were assumed linear. Python programming and ABAQUS software are utilized for process simulation and linking the FE model and genetic algorithm.

In the current paper, a micromechanical based model is presented to estimate the stress transfer in interphase of three-phase reinforced composites. The symmetric model consists of fiber, matrix and a layer in between them. In this study, composite constituents were considered as linear elastic materials. Also, the matrix was treated as isotropic material while the fiber and the interphase were considered as transversely isotropic materials. The stress distribution solutions for an intact model and partially debonded model are obtained. A pair of uncoupled partial differentiation equations were obtained in terms of unknown displacement components. The separation of variable with Eigenfunction expansion methods were used to derive the exact solution of the PDE’s. Analytical solutions for the free boundary conditions on the external surface of the matrix are obtained to simulate the pullout test. In both cases, numerical findings revealed a good correlation with the analytical results. By comparing the shear, radial and axial stress components become clear that three- phase composite adopts smaller amounts than of two- phase composites. Also, it was shown that the stress field in the partially debonded model has small quantities in comparison to the intact model.

Reinforcing of materials using carbon nanotubes are new approach for development of new and or advanced composites. In the meantime, the use of carbon nanotubes to reinforce cementitious materials, especialy reconstructing cement, is considered. The synthesis process of nanotubes on cement is the main problem in making the composite. In the paper, synthesis and characterization of cement-CNT composite produced by CVD process was investigated. The CVD process at 800°C using acetylene gas as a carbon source, argon as carrier gas and hematite iron oxide as a catalyst was performed. Wet impregnation method for preparing the catalyst bed of cement and iron oxide particles were used. FESEM, EDX, TEM and Raman spectroscopy were used to characterization CNTs/Cement composite and the size, morphology and quality of CNTs respectively. The growth yield of carbon nanotubes was determined by TGA. The results showed that the chemical vapor deposition method allows the deposition of carbon nanotubes with proper distribution of diameters and quality. It was also observed that most of the synthesized carbon nanotubes have open ends that represent the end growth of the carbon nanotubes. Finally the result of mechanical tests indicated that CNTs addition to the cement paste dramatically the increased compressive strength by bridging between cracks and filling pores.

In present study, production of Al/(Al2O3ɜ嗋棘) composite in Al-V2O5-NiO system with thermomechanical activation method has been investigated. For this purpose, the mixing of Al, V2O5 and NiO powders with two different weight fraction (P0: Al-18.9 V2O5-7.9NiO, P1: Al-13.3V2O5-5.6NiO) were grinded and densification was occurred. Differential thermal analysis method was used to investigation of phase transitions. Heat treatments was conducted on the raw comperest silenderical samples due to the peak temperature of the reactions, P0 raw samples heated at temperatures of 725,770 and 950 °C and P1 raw samples at temperatures of 725, 830 and 960 °C. XRD analysis and the microstructure of the sintered samples at temperature of 960 showed that the phases Al3V, Al23V4, α-Al2O3, Al2V3 in both sample as reinforcement is formed.in this temperature. The difference between P0 and P1 samples is that in the P0, AlNi phase and in P1 Al4Ni3 phase formed. Studies also show that by increasing temperature we have increase in the hardness and density. In P0, hardness and density values in this sample where much more than of P1.

In the present study, Al/Cu layered composite was produced through CRB method at room temperature, without lubricant and via using laboratory rolling machine by applying 60% reduction in thickness. Also mechanical properties, fracturgraphi and microstructure investigated through uniaxial tensile test, microharsness, scanning electron and optiv microscope. Results of carried out tests, showed the value of tensile strength and microhardness for Al/Cu layered composite compared to initial Al 5052 and pure Cu, increased that the main cause of this increase is applied high strain and cold working. Value of tensile strength for Al/Cu layered composite received 415 MPa that compared to initial Al 5052 and pure Cu 48% and 140% enhanced, respectively. Also microhardness calculated for each layers of composite individually and for Al and Cu increased 14% and 83% respectively. Results of SEM demonstrated that ductile fracture mechanism govern for Al/Cu composite such as initial samples, but the difference is that dimples for composite layers shallower and smaller compared to initial samples.

Due to stress concentration, adherends non-homogeneity (adherends materials, geometry and boundary conditions), and load transferring phenomenon, joints are the most critical locations in the structures especially composite structures. Enhance the strength of the adhesive joints and improve the dynamic behavior of the joints are the main goal of the most adhesive joints studies during the last decade. The effect of the step graded behavior of adhesive zone on dynamic behavior of composite T- joint is studied in present work. Finite element analysis (FEA) of carbon fiber reinforced polymer (CFRP) face-sheets, presented with ABAQUS 6.12-1 FEM code software. Loctite Hysol 3422, an epoxy adhesive, selected to bonding purpose and step wise behavior of adhesive region. Modal analysis and transient half-sine dynamic response of the composite T- joint are presented in this paper. Two verification processes employed to verify the dynamic modeling of manufactured sandwich panels and T-joint modeling. Step wise graded adhesive zone is a brilliant recommendation to control and improve the dynamic behavior of T-joints. The effect of the step wise graded adhesive zone on natural frequencies and mode shapes and transient response are compared for different topology of the step wise graded adhesive zone. It has been shown that the step wise graded adhesive zone cases changed the first natural frequency in range of 34 % and affected the mode shapes. Also the structural damping of the step wise graded adhesive zone cases and dynamic responses are smoother and more applicable.

In recent decades, composite materials have wide range of applications in different industries such as aerospace and automotive due to their high strength to weight ratio. Crash box uses as energy absorber in automobiles between bumper and chassis to prevent damage to passengers. Due to high importance of passenger’s safety, reduction of maximum load of crash box after crash is very important. In general, an ideal crash box has higher specific energy (SEA) and lower maximum load. Therefore, it is very important to have a predictive design tool to be able to simulate the response of thin-walled structures under impact or crash loading. In this study, at first to validate the numerical simulation, a composite crash box is simulated in Abaqus/Explicit, according to available experimental research and extracted force-displacement curve from numerical simulation is compared with available experimental results. After ensuring the solution method, in order to provide an overall strategy to reduce the amount of the maximum load of crash boxes, a composite crash box is modelled and the effects of three different triggers on collapse behavior, especially on the maximum load is evaluated. Results show that presence of trigger in simulated crash boxes has a positive effects on their performance.

Crack growth trajectory in V-notched specimens is investigated by polymeric round-tip V-notched Brazilian disk (RV-BD) under combined compressive-shear loading conditions both experimentally and theoretically. First, the experimental fracture trajectory of RV-BD specimens is obtained by means of 18 fracture tests for various notch opening angles and 0.5 mm notch tip radius. Then, by utilizing two methods, namely the extended finite element method (XFEM) based on the cohesive zone model and the incremental method on the basis of the maximum tangential stress (MTS criterion), the fracture trajectory is predicted. Predictions of both the methods and also the experimental observations show that although the V-notch is under compressive-shear loading conditions, fracture initiates due to the tensile stresses at the notch border and propagates to the external boundary of the specimen. The graphical agreement of the two predicted trajectories with the experimental one demonstrates the ability of both methods in predicting the fracture trajectory for V-notches under compressive-shear loading conditions.

In this paper, transient heat transfer analysis in composite metal cylindrical vessel will be investigated using the layerwise theory and differential quadrature method. For this purpose, five samples from the metallic cylindrical vessel and composite metal cylindrical vessel has been under transient heat transfer analysis.Thermal conditions of governing the issue has been extracted from a practical and experimental conditions. The aim of this research is study and investigate the behavior of heat transfer in the vessels mentioned. Therefore, the governing equations of heat transfer is achieved in a multilayered cylindrical vessel. Due to the different behavior of multilayer cylindrical in heat transfer, the analysis is to be done using the layerwise theory in order to obtain more accuracy. Then, the governing equations of heat transfer are derived for this vessel and are solved by differential quadrature method. In differential quadrature method, to solve the governing relations, These equations must be in the form of the matrix equations. The MATLAB programming code to be used to solve this matrix equations. After extracting result, temperature changes and heat transfer behavior in multilayer cylindrical vessel versus time have been discussed. To validate the resulting solution of the layerwise theory and differential quadrature method, modeling and numerical analysis of heat transfer in Abaqus finite element software done and the results of this software were compared with the solution of differential quadrature. Finally, the results of this study have been compared with exact solution of heat transfer equations in the several reference.