Advanced Materials Research Vols. 47-50

Abstract: The need for solid-waste management has pushed the development of alternative systems for recycling and revalue used plastic containers. Poly(ethylene terephthalate) (PET) is being widely used as raw material for beverage bottles. However, as has been widely reported, PET undergoes degradation and hydrolysis when reprocessed. On the other hand, poly(butylene terephthalate) (PBT) is another thermoplastic polyester with easy processability but high brittleness and cost. Hence, it has been blended with other polymers such as polypropylene to overcome its disadvantages. In this work, bentonite was incorporated into recycled PET and PBT/polypropylene blends by extrusion. Rheological and tensile properties and processability of the composites thus prepared were studied. Results showed a strong newtonean character of extrudates of recycled PET and higher viscosities and a more pseudoplastic behavior and improved reprocessability when bentonite was added to PET. Furthermore, inclusion of the filler increased its initial degradation temperature, as observed during rheological testing. All composites displayed a brittle behavior. However, the tensile properties of PET composites were not strongly deteriorated. There was a slight increase in the Young’s modulus values and in the tensile strength, with unnoticeable effects on the elongation at break. The Young’s modulus values of PBT/PP composites were not significantly affected.

Abstract: Analytical expressions for crack-tip higher order stress functions for a plane crack in a special functionally graded material (FGM), which has an variation of elastic modulus in 1 2 power form along the gradient direction, are obtained through an asymptotic analysis. The Poisson’s ratio of the FGM is assumed to be constant in the analysis. The higher order fields in the asymptotic expansion display the influence of non-homogeneity on the structure of crack-tip fields obviously. Furthermore, it can be seen from expressions of higher order stress fields that at least three terms must be considered in the case of FGMs in order to explicitly account for non-homogeneity effects on the crack- tip stress fields. These results provide the basis for fracture analysis and engineering applications of this FGM.

Abstract: The high order discontinuous asymptotic fields similar to the Williams’ solutions to crack problems in homogeneous materials are obtained by asymptotic analysis for an anti-plane problem in non-homogeneous materials and the crack at the physical weak-discontinuous interface. These results provide a theoretical basis for engineering application of weak-discontinuity fracture.

Abstract: Failure by delamination of composite laminates due to low velocity impact damages is critical because of the subsurface nature of delamination. Traditional methods such as stitching and Zpinning, while improving interlaminar properties in woven composites, lead to a reduction of the inplane properties. To alleviate these problems, use of Tetra Ethyl Orthosilicate (TEOS) nano fibers manufactured using electrospinning technique in fiber Glass-Epon composite laminates is investigated for their potential to improve the interlaminar properties. Electrospun coated fiber glass woven mats are impregnated with epoxy resin using Heated-Vaccum Assisted Resin Transfer Moulding (H-VARTM) process. The interlaminar properties of the nano engineered hybrid composites obtained using ASTM Double Cantilever Beam (DCB) tests and short beam shear tests are compared with those without the presence of electrospun fiber layers, to study their influence. The short beam shear tests revealed a 20% improvement due to presence of TEOS interlaminar electrospun nanofibers. It is also noteworthy that fibers cured at different temperature levels had variation in performance as observed in MSBS test results.

Abstract: Currently, titanium dominates the dental implant materials due to its strength and bio-inerrability. The use of titanium implant had demonstrated considerable surgical success. However, researchers are spontaneously pursuing better materials to achieve better osseointegration in the early stage of implantation. Recently, dental implants based on functionally graded material (FGM) were introduced in pursuit for the goal of enhanced bio-compatibility. The concept for FGM dental implant is that the property would vary in certain pattern to match the biomechanical characteristics required at different regions in the oral bone. However, mating properties do not necessarily guarantee better osseointegration and bone remodelling. There is no existing report available on the long-term effect of FGM dental implant on its hosting bone tissues. This paper aims at exploring this critical problem by using computational bone remodelling technique. The magnitude of bone remodelling due to use of FGM implant is identified over a healing period of four years. Comparisons were made between titanium and various FGM designs, the interesting differences were observed and the optimum FGM design was suggested based on the remodelling results.

Abstract: This study was numerically and experimentally investigated on improvement capture velocity for increasing inhalation efficiency of hood in local ventilation system. The inhalation efficiency of hood was studied to improve by increasing inhalation force of the hood that attached the new device named “Gas-Guide-Device (GGD)”. Also, harmful material that couldn’t inhale in hood was removed by increasing capture velocity at the edge of hood. For the numerical study, computational fluid dynamic (CFD) was used to predict the improvement of flow velocity with attached GGD in hood. To verify the numerical result, the flow velocity was experimentally measured using a hot-wire type anemometer. As a result of the numerical and experimental study for improving the effect of the GGD on the inhalation efficiency of the hood, it was verified that the capture velocity around the hood inlet was relatively higher for the hood with the GGD than for the one without it.

Abstract: This paper investigates on three-dimensional thermal deformation of aluminum casting tire mold applying metal casting method by numerical analysis and experiment. In this study, the numerical analysis was performed based on finite element method (FEM) in order to predict thermal deformation in tread part of tire mold by completely cooling about 50°C. For the numerical analysis, “COMSOL Multiphysics 3.3 Ver.” a commercial program for heat transfer and thermal-structural analysis, was used. In order to verify the results calculated by the numerical analysis, the experiment was carried out applying metal casting method on the same condition of numerical analysis. For the experiment, the temperature profile inside the aluminum casting tire mold was measured using thermocouples by completely cooling. When the temperature profile calculated by the numerical analysis and measured by the experiment were compared with each other, it appeared that was a slight temperature difference between the two results by latent heat of aluminum alloy, but their cooling patterns were almost similar.

Abstract: The anisotropy in mechanical strength and electrical conductivity in Cu-Ag alloy during cold rolling were investigated. The anisotropy in tensile strength and electrical conductivity was significant with increasing Ag content in Cu-Ag alloy. The cold rolled Cu-Ag alloys with higher Ag content have filamentary structure, which is composed of elongated eutectic phase and Cu matrix. In addition, the eutectic phase in Cu-Ag alloys with higher Ag content has a strong α-fiber texture. It can be mentioned that the eutectic phase in filamentary structure is promotes the anisotropy of electrical conductivity of Cu-Ag alloys. This strong a-fiber texture of eutectic phase was decreased by annealing process (300 OC for 1h), and the anisotropy in strength and conductivity was decreased.

Abstract: To develop Cu alloy with tensile strength of 800 MPa and electrical conductivity of 80 %IACS (International Annealed Copper Standard), the variation of mechanical strength and electrical conductivity in Cu-Ag alloy during fabrication processes including casting, solid solution and ageing treatment were investigated. Solid solution hardening leads to a large drop in electrical conductivity of Cu-Ag alloys due to super-saturation of Ag solute in Cu matrix. Ageing hardening gives rise to enhance both of the mechanical strength and the electrical conductivity. Therefore, it can be mentioned that the electrical conductivity of Cu-Ag alloys was affected dominantly by Ag solute in Cu matrix.

Abstract: ZnO microrods were synthesized on Si (111) sustrate by thermal evaporation at the temperature of 700 °C. Different growth environments bring to the different morphologies of the depositions. By analyzing the scanning electrical microscopy (SEM) images, a growth mechanism of the microrods is schematically put forward. Transmission electronic microscopy (TEM) images show that the perfectly epitaxial relationship between the ZnO nanorods and microrods.