Applied Mechanics and Materials Vol. 763

Abstract: This study is about the hybrid composite which used the woven Kevlar, long Kenaf fibre, and unsaturated polyester as the matrix. It focused on the mechanical characterization and properties of hybrid composite. The hybrid composites were fabricated by treated and untreated kenaf fibre and Kevlar as reinforcement in unsaturated polyester matrix using hand lay-up process. Effect of 6wt% of sodium hydroxide (NaOH) on the hybrid composites were analyzed using X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) analysis. The tensile and impact performance of the samples were tested according to the standard ASTM D3039 and ASTM D3763, respectively. Based on scanning electron micrograph (SEM) morphological examination, it revealed that the interfacial adhesion between the fibre surface and polymer matrix were improved. The results proved that the alkaline treatment can help to improve the mechanical properties compared to the untreated kenaf fibre.

Abstract: This paper presents the investigation of the probability of changes in the magnetic properties of nanomaterials in strong fields of charged particles, neutrons and gamma rays. Co_xNi_1-xFe₂O₄ nanoparticles were obtained by the hydrothermal method using polyethylene glycol. Investigation of the properties of this material showed that its magnetic properties depend on the concentration of Со²⁺. In this work it is shown that the nuclear reactions taking place in the crystal lattice sites can change the relative concentration of the components of test material and, accordingly, its magnetic properties, including the coercive force.

Abstract: Natural fibres are aimed to replace or at least to reduce the dependence of the industrial sector against low degradability of raw material. Hence, this study is performed to investigate the effect of stacking sequence and fibre orientation on the compressive properties of Kevlar/kenaf hybrid composites. Previous study suggested that treated kenaf fibres improved the fibre’s properties. Therefore, kenaf fibres was treated with NaOH of 6% concentration for 12 hours before rinsed and dried to be used in this study. The stacking sequence was varied for different weight percentage of woven Kevlar from 0 wt% to 23 wt%, while the kenaf fibres were arranged at 0° and 90° orientation, respectively. The compressive properties of the Kevlar/kenaf fibre hybrid composites were investigated using Instron Universal Testing Machine (ASTM standard D3410M). Stereo-zoom was used to identify the fibre orientation and the bonding between the fibres and matrix. For stacking sequence, the study showed that the arrangement of kenaf fibres on the middle part, “sandwiched” between Kevlar on the outer part, gave the best compressive performance. The sample in 0° orientation exhibited better compressive strength and modulus than 90° orientation. The outcome of this research has shown significant increase of compressive strength with the addition of kenaf fibre replacing the Kevlar.

Abstract: This study focuses on tensile properties and impact strength of coir fibre reinforced polypropylene composites under influences of fibre loading and various temperatures conditions. All samples were fabricated by using hot-press technique. Tensile and izod impact samples were prepared in accordance to the standard specifications as closely as possible. Three different ratios of fibre with matrix which were 10%, 20% and 30% were studied. The results revealed that 20% volume fraction of coir fibre demonstrated optimum tensile and impact properties. Significance reduction of impact strength under low temperature condition had been shown for all composites due to the brittleness of both fibre and matrix.

Abstract: In this work, nanoscale zinc substituted calcium phosphate ceramics substituted were synthesized by simple precipitation method, performed under alkaline solution of pH 10. Three different zinc concentrations (5%, 10% and 15 mol%) were incorporated into calcium phosphate ceramics with experimental ratios of (Ca+Zn)/P were all maintained at 1.67 for easier comparison. The phase composition and lattice parameters for each sample were determined by using X-ray diffraction (XRD) method. Other characterization techniques such as Fourier transform infrared (FTIR) and field emission scanning electron (FESEM) were also utilized to investigate material’s molecule internal bonds properties and powders morphology, respectively. Based on XRD results, zinc ions addition disturbed the calcium phosphate ceramics structure causing its crystallite size to become smaller as the amount of zinc increased. After the powders undergo calcination process, the bands of PO₄ in its FTIR spectra increased while the H₂O bands decreased. FESEM results showed that the powders are uniform but irregular in shape and tend to agglomerate with increasing zinc fraction.

Abstract: This paper reports on the compatibility of hydroxyapatite (HAP) combined with single based binder, palm stearin for ceramic injection molding in order to obtain the best properties. The feedstock was prepared at a powder loading of 62 Vol % using 5μm fine ceramic powder of hydroxyapatite and the binders consisting of 100% of palm stearin. The specimens underwent thermal de-binding and then sintered in an electrical furnace within a temperature range from 500°C to 1000°C. The resulting exhibit promising properties which the final product produced after the sintering process was successfully tested by mechanical testing. It is proven that even the specimen only consists of single based binder can form a complex shape without collapse just like the specimen obtained by the conventional binder system. Therefore, the fabrication also is more towards green processing technology and energy conservation due to the binder used was from natural local resources and used lower processing temperature at 50°C to 70°C for mixing and injection molding.

Abstract: This article is focused on SCM questions. Studied material - metashale belongs among artificial pozzolana with natural origin. Shale is clay mineral and by its burning at 700°C similar material as metakaolin arises. Metashale is used as cement replacement up to 60% in concrete production. By means of measurement of basic physical properties, mechanical strength and thermal characteristic the effect of metashale is determined. Concrete containing 20% of metashale shows improvement of studied properties except of thermal conductivity. The 40% of the SCM leads to concrete production with same properties as the reference concrete. And when 60% of the burnt clay is utilized, final values of studied properties shows little deteriorations. However all studied materials shows appropriate properties to be applicable in civil engineering branch as load-bearing concrete.

Abstract: One of the important characteristics of weld quality, which is influenced by welding parameters, is the hardness of the melted zone (HMZ). In this paper, experiments were conducted by Taguchi experimental design and Minitab 14 statistical software, and the interaction of input parameters was not taken into account. After collecting data, the signal to noise ratio (S/N) was calculated to obtain optimal levels for all input parameters. Then, using analysis of variance (ANOVA), the significance level of (P) for each input parameter was determined and validated for the hardness of the melted area. The results show that current intensity, welding speed, arc voltage, nozzle distance from work piece and thickness of magnesium oxide nanoparticles had respectively the highest impact on the hardness of melted zone.

Abstract: The submerged arc welding (SAW) process is similar to other welding methods, the quality of welded joints plays role as improves strength, stiffness and toughness of products. The purpose of this paper, modeling and optimization of the submerged arc welding process parameters is using Taguchi's method analysis of experiments. All analyses were carried out using Minitab 14 Statistical Software and the interaction parameters in this study are ignored. The experimental results show that this model can predict the output parameters with reasonable accuracy.