Abstract: Poly (lactic acid) (PLA) was modified through free radical grafting of itaconic anhydride to create reactive side-chain groups. Modified PLA was blended with Decoloured Novatein® (DNTP), a thermoplastic protein material using reactive extrusion to produce a degradable material with improved properties compared to neat Decoloured Novatein®. Varying ratios of blends were prepared. Blending DNTP with PLA was found to increase tensile strength between 22% to 538% and modulus between 201 GPa to 3193 GPa, whereas the strain at break decreased between 80% to 94% depending on the blend ratio. The glass transition temperature of the blends which was measured as the tan δ peak, also revealed an increase when compared to neat DNTP. Scanning electron microscope revealed an enhanced interfacial adhesion between the two phases in the blends with PLA-g-IA suggesting a more homogenous microstructure. The results show the possibility and feasibility of blending DNTP with PLA for use in agricultural and packaging applications.
Abstract: Durability of glass fibre reinforced polymer (GFRP) composite is an important research topic because the changes occur in GFRP composite with ageing can affect its properties and lifetime. For long term use, GFRP composites should be examined in real time and with reasonable in-service environments. However, this is not practical because the time involved would significantly delay product development and therefore, accelerated ageing technique is required. Conditioning in wet and elevated temperatures known as hygrothermal ageing is a very useful technique to evaluate the durability of GFRP composites in a reasonable timeframe. In this work, pultruded GFRP composites were aged in sea water and in dry conditions at 23, 55 and 75°C for 0, 8 and 20 months to assess the changes in shear properties (e.g. short beam shear strength, SBSS and transverse shear strength, TSS) and in glass transition temperature, Tg. After ageing in sea water for 20 months, SBSS was found to retain by about 101, 102 and 95% at 23, 55 and 75°C, respectively. On the other hand, SBSS was retained by around 106% after ageing in dry condition for 20 months at 55 and 75°C. TSS was found to retain by approximately 99, 95 and 91% after ageing in sea water for 20 months at 23, 55 and 75°C, respectively, whereas TSS of dry conditioned samples was retained by about 105 and 107% at 55 and 75°C, respectively. Tg, measured by dynamic mechanical thermal analyser, showed little change both in wet and dry conditions at different temperatures and time.
Abstract: Orientation of fibre preforms is an important factor that affects the properties of short natural plant fibre composites. In this paper, oriented short hemp fibre mats were produced using dynamic sheet forming and the fibre orientation distribution in the mats was analysed using ImageJ software as well as by a simple program developed on a MATLAB software package. The OrientationJ plug-in of ImageJ gave an orientation distribution curve with a peak at a predominant direction of 0° supporting alignment during dynamic sheet forming and from MATLAB software, a mean ratio of 0.64 was obtained for the oriented mats compared to 0.74 for an aligned bundles.
Abstract: In this paper, the TiAl/Ti laminated (MIL) composite was fabricated via hot-pack rolling of the as-forged Ti-43Al-9V-0.3Y (at.%) plates and commercial Ti6Al4V (wt.%) sheet at 1250°C and then annealed at 90°C for 6 hours. The composite was analyzed by XRD and SEM techniques, respectively. Results showed that the interface between Ti and TiAl in the composite was consisted of four different microstructure areas and the phase constitutions for each area were: area 1: acicular β-Ti and α2 phase; area 2: acicular α2 phase; area 3: acicular α2 phase and B2 matrix; and area 4: acicular γ, α2 phase and B2 matrix. The fracture toughness of the TiAl/Ti MIL composite was tested, showing that the KIC value was about 38.35MPa·m1/2 at room temperature and higher than that of the pure Ti-43Al-9V-0.3Y alloy, which had a value of about 24.72 MPa·m1/2. The possible toughening mechanism for the TiAl/Ti MIL composite was discussed.
Abstract: Vacuum-sintered billets of Ti-6Al-4V alloy from powder blend were extruded at two different temperatures: 1150 °C and 950 °C. The extruded material at 1150 °C was subjected to various heat treatments to obtain different microstructures: annealing in the β phase, β solution treatment and aging and α+β solution treatment and aging. The materials processed were characterised using scanning electron microscopy, X-ray diffraction and the mechanical properties were measured by tensile test. The microstructure of both extrusions are fairly similar, consisting of lamellar colonies, and the mechanical properties are also comparable, with yield strengths of about 1000 MPa, ultimate tensile strength of about 1100 MPa and elongation at fracture of 8-9%. The β annealing treatment, through coarsening the lamellar microstructure, reduces the strength of the alloy while keeping a high ductility. Both solution treatments and aging, which produces aged martensite and aged martensite and primary alpha, respectively, increases the strength and reduces the ductility. There is a trade-off between ductility and strength when it comes to tailoring the microstructure, and the as-extruded Ti-6Al-4V condition is the one with the best balance between strength and ductility.
Abstract: Sintering is a vital technology used for consolidation of metal and ceramic powders. The process is generally long and energy consuming because of the way in which heat transfer happens in electrical and gas furnaces. This study focuses on optimizing the sintering process of metallic powders, in particular titanium, using high frequency induction heating as alternative sintering method. Using electromagnetic induction and the associated Eddy current effect, the heat is generated directly into the electrically conductive object. Consequently, faster heating rates and lower heat loses are achieved. The purpose of this study is to understand the effect of process parameters, such as the powder compact density, on the efficiency of the induction heating and the properties of the sintered materials. The average heating rates recorded while heating to 1300oC are in the range of 3.5o to 15.3o C per second. Significant densification and consolidation, evident by the amount of closed porosity and increase in tensile strength was found in spite of the short heating time. The results show that the powder compact density plays a crucial role on the heating efficiency as well on the properties of the sintered material such as final density, porosity distribution and tensile properties. The samples with higher initial density showed tensile strength and ductility values comparable to those of high vacuum sintered and those specified by international standards for powder metallurgy Ti products.
Abstract: High strength, low density, good corrosion resistance and biocompatibility is the combination of properties that Ti and its alloys can provide for engineering applications. Its costs are the most important limiting factor for the widespread use of Ti. Cost reduction for Ti alloys can derive from the use of cheaper alloying elements as well as the use of alternative manufacturing techniques. In this study binary Ti-X alloys (where X = Cu or Mn) were formulated and produced using the conventional powder metallurgy route of pressing and sintering. These chemical elements were selected because they are β stabilisers and can be used to create α+β Ti alloys. The study shows that with the techniques and processing parameters used handable products without delamination can be pressed. Moreover, chemically homogenous materials with density and mechanical property values comparable to those of other wrought-equivalent Ti alloys produced via powder metallurgy were achieved.
Abstract: For the past fifteen years, there has been considerable interest in the use of nanofluids in various fields mainly in heat transfer applications. This paper investigated thermophysical properties of activated carbon nanofluids using hexane, water and ethylene glycol (EG) as base fluids. Experimental and qualitative observational tests were conducted to study the viscosity, specific heat capacity and stability of the nanofluids using arabinogalactan (ARB), sodium lauryl sulphate (SDS) and TritonX-114 as stabilising agents. The results revealed that the addition of ARB to activated carbon-water (C/H2O) nanofluids yielded nanofluid stability for up to 39 days. However, ARB decreased the heat capacity of C/H2O nanofluid. C/H2O nanofluid viscosity decreased with an increase in shear rate. On the other hand, results revealed that C/C6H14 viscosity increased with the increase in shear rate specifically for high shear rate values. C/H2O heat capacity was enhanced by 6.1% compared to C/EG that decreased by 6.3%. Keywords: Nanofluids; Viscosity; Specific heat capacity; Surfactant; Stability.
Abstract: The demand for high accuracy on automated harvesters is getting higher. While system accuracy is lowered by vibration resulted when a robot with sensors and arms is running on the field. Applying suspension system onto these automated harvesters is a solution to reduce the vibration effects and assure required accuracy. This paper presents a model of the suspension system for a robotic asparagus harvester. The simulation results showed that the peak value of vibration was reduced to an acceptable level. Most importantly, the peak deflection of a vibrated platform was decreased to a required range as well. At the end of this paper, a conclusion is drawn. A suspension system is suggested to reduce vibration effects and improve the accuracy of both sensors and picking arms for mobile manipulators. In the future, this suspension system will be fabricated and installed onto a robotic asparagus harvester to validate this proposed model.