Applied Mechanics and Materials Vol. 761

Abstract: The critical fracture toughness parameter K_ΙC of AZ61 magnesium alloy was determined on the three point bent specimens with notch designed according to ASTM E399 standard. Five specimens having different thickness, i.e., 2, 4, 6, 8 and 10 mm were considered in order to evaluate the effect on fracture toughness. The stress intensity factor range ΔK was constant ~1x 10^-8 for every specimen until the critical crack length reached half of the width of the specimens. The fracture test was done with the speed rate 0.12-0.15 MPa√m/sec until the specimens broke. The experimental results showed that the critical plain strain fracture toughness K_ΙC is 12.6 MPa√m and the highest plain stress fracture toughness K_C is 16.5 MPa√m.

Abstract: This paper presents effects of heat treatment on toughness, hardness and fatigue strength of aluminum alloy 6061. The alloy specimens were heat treated in the furnace at different temperature levels and holding times; and then cooled in different media (water and oil). The mechanical properties such as hardness, impact and fatigue were examined using standard method. Result shows that mechanical properties of aluminum alloy can be improved by the heat treatment. It was found that through ageing processes at temperature 160 °C for one, three and five hours, decreased the hardness, while increased the toughness. The fatigue strength was decreased when the number of cycles increased. The fracture surfaces between specimens have a different appearance before and after heat treatment.

Abstract: Mechanically ground recycled carbon fibers (rCFs) reinforced polymer composites were investigated in this paper. The rCFs were collected from the woven prepreg waste. The as-received (rCFs-AR) and cyclic cryogenic treated (rCFs-T) carbon fibers were incorporated separately in the epoxy matrix composite. The objective of this study is to study the wear behaviour of the epoxy composites with respect to the as-received and treated rCFs. Prior to the composite fabrication, the surface morphologies of rCFs-AR and rCFs-T were examined with the scanning electron microscope (SEM). It is found that the cryogenic treatment is effective in removing the epoxy resin from the carbon fiber due to the mismatches in the thermal expansion at the interface of rCFs and epoxy. The rCFs-AR and rCFs-T were homogeneously distributed in epoxy resin through ultrasonication. The void-free samples were then fabricated using vacuum casting technique. Micro Pin-on-disc Tribotester (CM-9109) was used to test the tribological behaviour of the polymer composites. The coefficient of friction (CoF) and wear rate of epoxy composites revealed that the reinforcement effect of rCFs-T is better than that of the rCFs-AR as the incorporation of rCFs-T decreases the CoF and improves the wear resistance of epoxy composites in comparison with rCFs-AR. The tribological results clearly showed that the rCFs was a valuable product worth to be reused as reinforcement in the new composite, as the incorporation of treated rCFs was effective in improving the tribological properties of the epoxy composites.

Abstract:

A research on the application of calcium hydroxide as a binder for briquetting of durian peels has been performed. The main aim of the present research is to improve the structure of the briquette and to observe basic fuel properties of durian peels in the presence of calcium hydroxide. The carbonization of durian peels was carried out at 370 °C for one hour. Durian peels briquette was characterized by the proximate analysis, calorific value, compressive tests and Fourier transform infrared (FTIR). The briquette was formed by the cyclindricalmould and hydraulic press.The comparison of the compressive strength between durian peels briquette with and without calcium hydroxide as a binder was in the range of 11.41 MPa to 17.38 Mpa. The calorific value of the durian peels briquettevaries from 4968 to 5883 cal/g. The calorific value results show that the durian peels briquette has strong potential to be applied as solid biofuel.

Abstract: In pultrusion process, one of the major decisions to be made by the manufacturing engineer is about the setting of manufacturing process parameters such as pulling speed, gelation temperature, curing temperature and CaCo₃ filler loading before the manufacturing process is commenced. The objective of this paper is to report on the optimization of the manufacturing process parameters during pultrusion process of kenaf fibre reinforced vinyl ester composites. Besides, the paper reveals the best combination parameter and the most contributed parameter in process of pultruded kenaf reinforced vinyl ester composite through analysis of variance (ANOVA).

Abstract: The nanostructural characteristics of direct-current magnetron sputter-deposited Ni₄Al alloy films were studied during in situ isothermal annealing in a transmission electron microscope (TEM). An expansion of the lattice by nearly 5% was observed for the synthesized films in their low-thickness and as-deposited state. The lattice size approaches the bulk value when the film thickness increases or after vacuum annealing heat-treatment. The Ni₄Al films have a nanocrystalline structure in which the ordered L1₂ phase appears upon annealing at above 500°C. A grain coalescence trend was found for the Ni₄Al films during the in situ annealing above 500°C. This can be the main reason for the abnormal grain growth of these films at these high temperatures.

Abstract: Tyre is one of the most crucial components in a vehicle structure not only to have the vehicle running smoothly on the road, but also to provide physical and acoustic comfort for the passengers. But, since the day the inflatable tyres were invented, sudden loss of air in a tyre acts as a major problem associated with tyres; and are still being treated to date by professional researchers and giant tyre manufacturers. The phenomena where tyre experiences natural pressure loss over the time is called air permeation which causes tyre to deflate on its own. Besides reviewing the primary theories and findings that contribute to natural air permeation that literally causes the pressure drop of an automotive tyre, this paper also reveals the experimentally validated results of the significant factor which contributes to air permeation of an automotive tyre. Additionally, a relevant nanobased solution to reduce the air permeation rate to stop the tyre deflation is also highlighted to establish the way forward total solution suiting wide range of tyres used on domestic cars.

Abstract: Biomass-derived materials such as kenaf pulp and wood chips are a perfect candidate to produce magnetic paper. Furthermore, by using biomass waste, such as paddy straw, sugarcane, bagasse and durian shell, the cost of producing magnetic paper can be further reduced while giving added value to the waste. This paper investigates the potential of producing magnetic sheet from durian shell. Initially, durian shells were dried before undergoing the pulping process. The resulted sheet was then combined with magnetic particles, the nanomagnetite using either lumen loading or in-situ co-precipitation to produce a magnetic composite sheet. After being loaded with magnetic particles, the composite sheets were tested in terms of the homogeneity of the magnetic particles in the samples, degree of loading of the magnetic particles and the magnetic properties of the samples. Results obtained show a great success in producing the magnetic sheet from durian shell waste and nanomagnetite particles. It was also found that the lumen loading method gives better magnetic properties compared to the in-situ co-precipitation method.

Abstract: Green composite material has become the most desired material to replace polymer composites made from fossil oil. Besides having advantages over its biodegradability and quality performances, the material sources are abundant and renewable. Therefore, this research focused on developing green composite which is derived from a combination of pineapple leaf fibers (PALF) and Polylactide (PLA). PALF is extracted from pineapple leaves which are easily found during harvesting pineapple plantation. In order to study the influences of different fibres characterization, the fibres were extracted from different types of pineapple available in Malaysia, namely Moris Gajah, Jasopine, Maspine, and N36. The main objective of this study was to investigate the physical and mechanical properties of this green composite. The physical testing was carried out to determine water absorption while the tensile and bending tests were conducted for mechanical testing. For the purpose of comparing the material properties, PALF reinforced polypropelene (PP) was developed too. Based on the result, Jasopine fibre shows the highest tensile and flexural strength for the combination of both polymers in comparison to the other types of PALF.

Abstract: Carbon fiber reinforced thermoplastics are in demand for high performance composites, particularly for the aircraft industry. Waste disposal of carbon fiber in the form of off-cuts, out of life of prepreg and end-of-life components lead to the environmental pollution. This study focuses on the processing and characterization of carbon fiber prepreg comminutes reinforced polypropylene (PP) produced by melt compounding using an internal mixer. In this study, end-of-life carbon fiber prepreg were crushed into fine fibers and dried in oven at 220°C for one hour. It was divided into two types; (1) partially cured carbon fiber prepreg (c-CFP) and, (2) fully cured carbon fiber prepreg (c-CF). The composites were prepared by melt compounding in a Haake internal mixer at 180°C, 50 rpm for 10 minutes. Samples were tested for tensile properties (ASTM D638) and the morphology of fractured surface was observed using Scanning Electron Microscopy (SEM). Increasing carbon fiber in polypropylene was found to increase the Young’s modulus of the composites, but decreased the tensile strength. However, the tensile strength of composites with c-CFP were observed to surpass the neat PP at every loading level. Whereas for composites with c-CF the tensile strength was comparable to the neat PP only within the range of 3 – 5 wt.%.