Key Engineering Materials Vols. 471-472

Abstract: Novel noncross-linked low density polyethylene (LDPE) foams were produced by extrusion process. In this study the effects of Organophilic Montmorillonite (OMMT) nanoclay (DK1) on thermal conductivity, flame retardancy, morphological and mechanical properties of LDPE foams have been investigated. Nanoclay dispersion in LDPE foam structure was examined by X-ray diffraction (XRD), microstructure was observed by an optical microscope and analyzed by Bel View image analyzer, thermal conductivity was studied by a simple transient method, mechanical properties was investigated using a tensile-compression Zwick-Roell machine as well as the flame retardancy of the samples was examined by flammability test. The optimum nanoclay content was determined by comparison of the properties in nanocomposite and neat LDPE foams. Due to the presence of nanoclay in the foam and decreasing the cell nucleation energy around the nanoclay, the average cell size was decreased as well as the cell density and microstructure uniformity was increased. In XRD patterns of LDPE nanocomposite foams, OMMT (DK1) characteristic peak was not observed as evidence of nanoclay intercalation-exfoliation in the polymer matrix, which led to the production of foams with homogenous microstructure. Furthermore, this nanocomposites showed lower thermal conductivity compared to neat LDPE foam, which can be attributed to the cell size reduction as well as narrow cell size distribution in nanocomposite foams. Compression test results demonstrated that LDPE nanocomposite foams with proper clay contents have improved mechanical properties (Young’s modulus, compressive strength). Furthermore due to the presence of DK1 nanoclay, LDPE foam showed a good char formation as an evidence of their flame retardancy.

Abstract: In the current study, the critical buckling of functionally graded plates (FGPs) subjected to thermal loads is evaluated using the finite strip method based on the first order shear deformation theory (FSDT). The material properties of these plates are assumed to vary in the thickness direction of the plate according to the power law distribution in terms of volume fractions of the constituents. The plates’ boundary conditions are assumed to be simply supported in all the edges or clamped in side edges and simply supported on the ends. The fundamental eigen-buckling equations for the plates are obtained by discretizing the plate into some strips, called functionally graded strip (FGS). The solution is obtained by the minimization of the total potential energy as well as solving the eigenvalue problem. The effects of material gradient index, aspect ratio and different thermal loadings (i.e. uniform temperature rise and nonlinear temperature change across the thickness) on the critical buckling temperature difference will be presented in some graphical forms.

Abstract: Recently glass fibre reinforced polymer (GFRP) tubular piles have been developed for civil engineering applications instead of conventional concrete piles. Considering their suitable applications, the new polymer based filling materials are being developed at the University of Southern Queensland as a part of work done for timber pile rehabilitation. This ongoing project aims to replace portion of the deteriorated timber pile by using GFRP piles. Due to good compressive strength, pumpability and workability, the new polymer base materials are to be filled in between GFRP pile and existing timber pile base. An ongoing research program has been initiated to improve fundamental understanding of these materials and to provide the knowledge required for their broad utilization. In this development, sample trial mixes were considered based on several weight percentages of polymer resin, fly ash and sand. Material parameters such as compressive strength, stiffness, shrinkage and gel time were achieved from the experimental investigation. It has been found that most polymer based trial mixed fillers have high compressive strength and considerable plastic region with more than 10% strain. These results imply that the polymer based filling materials are suitable for both compression and tensile loading situations. However, the behaviour of fillers with GFRP pile connector under different loading conditions is yet to be fully understood.

Abstract: Clay has an important role in making green sand casting mould beside water. Clay acts as binders, holding the sand grains together. Water is needed to activate the clay bond. Without the addition of water on clay, no strength would be achieved on sand mould, as the sand and clay would be just two dry materials. Bentonite clay was used in this study. Adequate clay content with suitable moisture in moulding sand is important for optimum strength and casting quality. Too little or too much clay will not give proper strength. Green compression strength is one of the mechanical properties to be considered for making green sand casting mould. The green compression strength of foundry sand is the maximum compressive strength that a mixture is capable of sustaining when prepared, rammed and tested according to standard procedure. For this study, test is conducted according to Foundry Sand Testing Equipment Operating Instructions from Ridsdale and Dietert. Result from this study indicates that tailing sand has potential for making green sand casting mould in term of green compression strength. Other factors that must be considered are permeability and shatter index.

Abstract: In this study, electron beam irradiated (EB) was applied as a crosslinker agent for both pristine high density polyethylene (HDPE) and HDPE/ ethylene propylene diene monomer (EPDM) nanocomposite systems. The doses rate for EB irradiated technique were varied between 50, 100, 150 and 200 kGy. The nanocomposites systems were first prepared via melt intercalation method with different organophilic montmorillonite (OMMT) loadings. It was found that, with 4 vol% organophilic montmorillonite (OMMT) loading, the barrier resistance of nanocomposite against oxygen transmission was significantly enhanced by EB irradiation dose rate of 100 kGy. The oxygen transmission for nanocomposite was reduced by 23.48%. The interplanar spacing, d-spacings of OMMT in nanocomposites were monitored using x-ray diffraction (XRD) and the extent of delamination was examined by transmission electron microscope (TEM). The wide angle of XRD patterns showed the increased interplanar spacing, d of clay layers, indicating enhanced compatibility between polymer matrix and OMMT with EB irradiation. TEM photomicrographs illustrated the mixed intercalated and partial exfoliated structures of the nanocomposites with the irradiation process.

Abstract: This paper reported the interfacial shear strength (IFSS) between kenaf fibre (KF) and polylactic acid (PLA) matrix which was measured using microbond tests device. The value of IFSS obtained in PLA-KF is comparable to other polymer with natural fibre reinforcements. The properties of single kenaf fibre was determined from tensile tests and also described in this paper. From single kenaf fibre properties, various mechanical properties can be estimated for various applications.

Abstract: Environmentally friendly nanocomposites comprising of cellulose and montmorillonite (MMT) were prepared via a green solvent, ionic liquid, 1-butyl-3-methylimidazolium chloride (BMIMCl) using solution casting method. The cellulose concentration and MMT content were varied according to predetermine formulation. The regenerated cellulose nanocomposites were characterized using X-ray diffraction (XRD). The thermal and thermal oxidative properties of regenerated cellulose nanocomposites were studied by thermogravimetric analysis (TGA). Mechanical properties of the nanocomposites films were investigated by tensile strength measurements. The intercalation and exfoliation of MMT in the cellulose matrix were confirmed by XRD results. TGA results showed an increment in degradation temperature and char yield for the nanocomposites. Multistep TGA graph was observed for degradation under air. The results indicated that the addition of MMT up to 6 wt% in regenerated cellulose matrix improved the tensile properties.

Abstract: One-dimensional nanostructures, like nanofibers, nanobelts, nanotubes, nanorods have been regarded as a new class of nanomaterials that have been attracted as the most promising building blocks for verity applications in the last few years. As one type of important structures with intensive research efforts have been devoted to the production and investigation of the metal oxides. Metal oxide nanofibers have different potential to play an essential role in a series of application such as optics, nanoelectronics, catalysts, sensors, storage, optoelectonics, and full cell. Copper oxide nanostructures is a promising semiconductor material with potential applications in photochemical, electrochemical, electrochromic especially in water splitting, catalysts, and fabrication of photovoltaic devices. In this paper electrospinning method via sol-gel was used to fabricate copper oxide nanofibers. Copper oxide nanofibers with different morphology were synthesized by different calcinations temperature. In this paper, effective parameters such as voltage, concentration of precursor and different calcinations temperature were characterized by thermal gravimetric analysis, scanning electron microscopy (SEM), Transmission electron microscopy, x-ray diffraction(XRD), Fourier transform infrared spectroscopy (FTIR) and Brunauer Emmett and Teller (BET).

Abstract: The effects of the consolidation pressure on the properties of novel Cu-15vol% TaC composite was investigated. The copper-based composite has been prepared using a high energy planetary mill via in-situ route. A mixture of copper, tantalum and graphite powder was mechanically alloyed for milling time of 8 hours at speed of 400 rpm. The as-milled powder was consolidated by cold pressing under various pressure (i.e. 100, 200, 300 and 400 MPa) at room temperature and sintered in argon atmosphere at 900 °C for an hour. TaC phase was formed in copper matrix after sintering process. An increase in consolidation pressure resulted in an increase in hardness, electrical conductivity and density of the composites. The changes of bulk properties of the in-situ Cu-TaC composite were correlated to the formation of TaC phase and a reduction of porosity which led to an increasing in densification.

Abstract: Nowadays, mechanical alloy (MA) method has turned up as one of a new and applicable method for metal matrix composite fabrication due to some advantages such as the ability to form nanocrystalline structure with improved properties. In this work, different milling speed of MA process (100, 200, 300 and 400 rpm) was performed on Fe-17.21wt%Nb-2.23wt%C with milling duration of 10 hours. The mixture was pressed and sintered at 1300oC into a pellet form. Investigation by X-ray diffraction, measurement of hardness and density were carried out. High milling speed resulted on crystalline-to-amorphous transition of XRD peaks of Fe and NbC phases. Different level of MA at different speed also produced fine NbC particles and strain hardening which resulted in increase value of hardness. The presence of pores, particularly in the composite with high milling speed, decreased the density of Fe-NbC composite.