Applied Mechanics and Materials Vols. 229-231

Abstract: We present the remarkable performance improvement of organic solar cells upon incorporating N- or B-doped carbon nanotubes (CNTs) into the organic semiconductor active layer. A small amount (0.2-5.0 wt%) of doped multi-walled CNTs are added to the bulk-heterojuction of poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl) propyl-1-phenyl[6,6]C61 (PCBM). Unlike undoped metallic multi-walled CNTs, which cause undesired electron-hole recombination, N- or B-doped CNTs uniformly dispersed in the active layer selectively enhance electron or hole transport, respectively, and eventually help carrier collection. Specifically, the incorporation of 1.0 wt% B-doped CNTs results in a balanced electron and hole transport and accomplishes a power conversion efficiency improvement from 3.0 % (conventional control cells without CNTs) to 4.1 %.

Abstract: This study had been carried out to investigate the effect of micron size Ni particle addition on the microstructure, melting behavior and mechanical properties of the ternary Sn-9Zn solder alloys. Different weight percentage, viz. 0.25, 0.5 and 1 of micron size Ni particle was added in the liquid Sn-9Zn alloy and then cast into the metal mold. Melting behavior was studied by Differential Thermal Analyzer (DTA). Microstructural investigation was conducted using Optical and Scanning Electron Microscope (SEM). Tensile properties were determined at a strain rate 3.00 mm.min-1. The results indicated that Ni addition increased both the melting point and solidification range of the Sn-9Zn solder alloy. The microstructures of newly developed ternary Sn-9Zn-xNi solder alloys consisted of fine needle-like α-Zn phase dispersed in the β-Sn matrix. It was found that small amount of Ni (0.25 wt. %) addition refined and dispersed the Zn needles throughout the matrix. Besides, enhanced precipitation of Zn in the β-Sn matrix was also observed. All these structural changes increased the hardness and tensile strength of Sn-9Zn alloy with the addition of Ni particle to a certain amount.

Abstract: Research on the use of natural fibers as replacement to man-made fibre in fiber reinforced composites have received more interest and opened up further industrial possibilities. Natural fibre presents many advantages compared to synthetic fibers which make them attractive as reinforcements in composite material. They come from abundant and renewable resources, which ensures a continuous fibre supply and a significant material cost saving to the plastics, automotive and packaging industries. The paper reviews the previous and current research works published in the field of natural fiber reinforced composite material with special reference in mechanical properties of the natural fiber reinforced composite.

Abstract: In this study a two dimensional thermal Lattice Boltzmann model with nine velocities was used to study the flow pattern and thermal field inside a T-micromixer with a porous block. The effects of porosity of porous block and flow Reynolds number were investigated. The results showed that better mixing between hot and cold flows and more heat transfer to horizontal walls in contact with porous block in lower porosities; due to the fact that in lower porosities the effective thermal conductivity of porous block increases. In lower porosities due to higher mixing rates and thermal gradient the entropy generation will increase. According to results it was observed that model with lowest porosity has the maximum mixing rate between two entering hot and cold flows and maximum dimensionless entropy generation.

Abstract: Silicon nitride ceramic has been used in various engineering applications such as bearings, rollers, and exhaust valves for automobiles because of its corrosion resistance, high-temperature strength and low density. LAM (Laser assisted machining) has recently been considered as an alternative and effective process for machining ceramic materials. The laser heat sources in laser assisted milling processes are irregularly varied according to shapes of workpieces. Therefore, prediction and analysis of preheating temperature is difficult. In this study, the thermal analysis and experiment were performed to evaluate the surface temperature distribution of silicon nitride according to laser power. In addition, the preheating temperature was predicted by analyzing the results of the thermal analysis.

Abstract: Due to significant amount of applications in industries, composite materials and structures are subjected to many different types of loading. One of the most common types of these loading is radial patch loading. Due to the complexity, calculation of radial shell deflection is the main character of the cylinder behavior when subjected to patch loading. The aim of this study is to investigate the mechanical behavior of composite cylindrical shell subjected to radial patch loading. The radial deflection of the laminated shell is investigated in detail where analytical and finite element methods (FEM) are used. The results through both approaches are compared to validate the accuracy of the analytical method. This is followed by a parametric study to determine the effect of some operation parameters on radial displacement. The results show close agreement between the analytical and numerical methods.

Abstract: The ring opening of -valerolactone (GVL) with amine compounds was reported as a promising molecular engineering tool to synthesize precursors for new bio-based polymers such as polyurethanes (PUs). Experimental work on the synthesis of polymers based on GVL/1,2-ethanolamine and GVL/1,2-diaminoethane adducts, and di-isocyanates (1,4-phenylene-di-isocyanate (PDI) 2,4-toluene-di-isocyanate (TDI) and hexamethylene-di-isocyanate (HDI)) is described. The polymers were characterized by FTIR, 1H-NMR, 13C-NMR, elemental analysis and GPC. The best polymerization results were obtained using TEA as the catalyst, DMA as the solvent and a temperature of 140°C for the reaction of the GVL/1,2-aminoethanol adduct with TDI. A polymer with a molecular weight (Mw) of 156 KDalton was produced in 97% yield.

Abstract: The advantages of polymer materials such as high strength and stiffness to weight ratio, corrosion resistance and manufacturing flexibility have increased the industry demands to utilize them in high performance applications. Designing polymer structures depends on a high understanding of their hyper-elastic behaviour, therefore investigating the mechanical behaviour of polymers is necessary. In this paper, the nonlinear behaviour of epoxy polymer is examined under upsetting test. The main aim of the study is to analyse the effect of strain rate on the mechanical behaviour of epoxy polymer. The cylindrical polymer epoxy specimen, 20mm in length and in diameter, was manufactured. The upsetting tests provided quasi-static compressive loads which were adjusted in the loading rates of 0.1, 1, 50, 100, 200 and 500 mm/min. The loadings were continued until complete fracture was observed. Each loading rate was repeated for at least 3 specimens to ensure a reasonably good statistical sampling. The average data of each test is used to produce the load-displacement graphs of the specimens, from which stress-strain curves are extracted to show the behaviour of epoxy polymer. The results show a 37% increase of yield stresses when the loading rate is increased from 0.1 to 500 mm/min and the yield strains increase by 26%. The stress-strain curves are nonlinear where the slope increases when the loading rate is raised from 0.1 to 100 mm/min but then decreases when the rate is further raised from 100 to 500 mm/min. The maximum load that can be sustained is increased with loading rate. This can be due to the microstructure deformation response of epoxy polymer. This polymer is categorised as large-strain material by showing exhibiting large deformations under different rates of compression loading.

Abstract: In the past few decades, design development of high performance machines and devices encouraged industries to utilize advanced materials such as polymers. Special mechanical features of polymer materials such as high strength to weight ratio and etc have increased scientists demands to investigate the nonlinear behaviour of polymers. One of the challenges in mechanic of polymers is to introducing a model that is competent to predict hyperelastic deformations based on long-strain behaviour of polymers. In this study, a comprehensive research is performed on introduced mechanical models for polymer materials. The major attempt was on introducing an appropriate model among the existing models, capable enough to predict mechanical behaviour of high density polyethylene under monotonic compressive load. The procedures of simulation and experimental tests are performed to examine the load capability of the model for high density polyethylene. Several compression tests are performed on High Density Polyethylene cubic specimens to extract the full stress-strain response of the high density polyethylene. Moreover, strain gauge is used in experimental tensile test to determine Poisson’s ratio. Simulation procedure is performed using ABAQUS 6.9EF for a comprehensive analysis and discussion on hyperelastic deformation. The simulation procedure is confirmed and verified perfectly by experimental data. The comparison between experimental result of compression test under monotonic load and finite element simulation of this test is remarkable to know about behaviour of HDPE to use in other structural and mechanical application.

Abstract: The existence of outliers can produce false harmonic frequency components in data processing for vibration signal of tracked vehicle.The paper uses the Wright standards to judge details coefficients of outliers and calculates new details coefficients to replace the ones of the outliers by weighted coefficient method.The signal can be reconstructed with new details coefficients .The results show that the new method can retain the maximum information of singal after eliminating the outliers , meet the data distribution and reduce variance.