Applied Mechanics and Materials Vol. 493

Abstract: Dispersion of carbon fiber in cement matrix is one of main challenges for fabricating carbon fiber reinforced cement based materials. In this study, the dispersion of carbon fiber was improved by pre-dispersion of carbon fiber in basic aqueous solution using different concentrations of CMC. The relationships of CMC concentration and pH solution toward carbon fiber dispersion in aqueous solution was evaluated by UVvis spectroscopy. In order to understand how carbon fiber is dispersed in cement matrix, morphology fiber carbon reinforced composite was examined. Experimental results show that aqueous solution of CMC is effective to disperse carbon fiber. In addition, dispersion of carbon fiber increases with increasing of pH of CMC solution.

Abstract: The objective of this research is to characterize the effects of heat treatment such as quenching, tempering and TiN coating on mechanical and physical properties of duylos 2510 steel. These mechanical properties include wear rate, hardness, impact toughness, whereas physical properties are microstructures. Duylos 2510 steel is a cold work tool steel and has chemical composition (wt %) of 1C; 0,6 Cr; 0,1 V; 1 Mn; 0,25 Si and 0,6 W.Quenching process has been conducted by heating the specimens on austenite temperature of 800 °C with the soaking time of 30 minutes and then cooling these specimens in oil medium. Tempering process was done at temperatures of 100, 200, 300, 400, 500 dan 600 °C with holding time of 2 hours.TiN coating has been deposited on substrates by sputtering technique of Physical Vapor Deposition at temperatures of 100, 150, 200 and 250 °C with sputtering time of 45 minutes. The mechanical and physical properties have been characterized by wear test, Vickers micro hardness test, Charpy impact test, and metallography test. This research was performed at room temperature and the major parameters of this research were tempering and sputtering temperatures.The results show that tempering temperature variations give significant modification of mechanical properties. In general, the Vickers micro-hardness decreases if tempering temperatures of the specimen increase. The highest Vickers micro-hardness of TiN coatings is 290 HV_0,01 for the specimen having sputtering temperature of 200 °C. Wear rate and impact energy increase if tempering temperatures increase. The results also show that the Vickers micro-hardness of coated specimens is higher than the micro Vickers hardness of non-coated specimens

Abstract: This paper works on the curvature composite structure for wing leading edge application using fabric carbon/epoxy material subjected to impact loading. At first stage, rigid spherical projectile and elliptical panel with were used. The impact testing has been carried out by varying the radius of curvature, the thickness of the panel and different stacking sequence. The experimental results show the trend of specific energy absorption capability of structure in function of the radius, thickness of panel and carbon fiber directions.

Abstract: Acoustic emission (AE) has been applied to study the fracture mechanics of concrete and other cementitious materials. In this paper, the AE hit generation behaviour is employed to investigate the fracture of high strength mortar containing basalt fiber under compression. A variety of amount and length of basalt fiber were used in mortar mix. Result shows that there is no significant effect observed on behavior of AE hit generation due to the differences amount and length of basalt fiber in mortar. All indicates the similar behaviour that can be described into three stages. At the second stage when maximum load starts to occur, AE hits are generated significantly indicating nucleation of many cracks. Materials failure in ductile manner since AE activities still can be recorded at long after post peak behaviour.

Abstract: The use of Myrmecodia Pendans (MP) extract as mild steel corrosion inhibitor in 3.5% NaCl media was investigated using weight loss and potentiodynamic polarization methods as well as characteristics analysis of the Fourier Transform Infra-Red (FTIR). Obtained data from weight loss and potentiodynamic polarization methods has shown the value of inhibition efficiency (% IE) is proportional toadded inhibitor concentration. Tafel constants data indicates that MP extract can act as cathodic and anodic inhibitors (type of mixed inhibitor). FTIR analysis also demonstrates the characteristics of MPextract. Occured inhibition mechanism was in the form of inhibitor adsorption process on metal surfacethat allegedly preceded by physical adsorption followed by chemical adsorption. Chemical adsorption is conceivable since metal surface scoping elevates as the increasing of inhibitor concentration.

Abstract: Nozzle is one crucial part of rocket. In this research, the nozzle was made by AISI 4340 coated by termal barrier coating (TBC). The TBC material is Al₂O₃SiO₂ composite, with different variation: Al₂O₃ 20% SiO₂; 70% Al₂O₃ 30% SiO₂; and 60% Al₂O₃ 40% SiO_2. The aim of this research to observe the composittion which will produce optimum adhesive strength and the most widely formed mullite phase. Mullite is an expected phase formed from composite and it has thermal resistance during 1300°C. Coating process was conducted by flame spray with variation of plies. The effect ratio, plies, microstructure, phase, and adhesive strength of TBC were investigated using Scanning Electron Microscope (SEM), X-ray diffraction (XRD),) and adhesion testing. The results showed that the highest adhesive strength was 16 MPa for 20%SiO2 with 2 plies. The highest mullite forming was TBC. After heat treatment, it was found that the mullite phases were most widely formed at a composition of TBC 30% SiO₂-70% Al₂O₃.

Abstract: Micro Metal Injection Molding utilizing 316 steel nanopowder with 100 nm in mean size was investigated to fabricate micro part. The nanopowder was used since its advantages to produce better surface roughness and detail structure in the micro part fabrication. During nanopowder preparation, thin oxide must be formed intentionally to avoid powder burnt before its exposed to the air during mixing with the wax binder system. Unfortunately, this oxide still exist after sintering and decrease the mechanical properties (ductility and densification) by the formation of secondary phase which detected as chrome oxide. In this paper, deep elaboration for oxide characteristics and the ways to reduce it by vary the sintering parameters and in Hydrogen atmosphere were described briefly. Here, we infer by reducing the heating rate, increasing the sintering temperature and utilizing the Hydrogen atmosphere can be effectively optimize the utilizing of nanopowder for micro part fabrication.

Abstract: The effect of electron beam irradiation on mechanical properties of Ethylene vinyl acetate (EVA) with polyamide 6/high density polyethylene/HDPE-g-MAH and montmorillonite (MMT) were prepared by melt blending the characterization were investigated. The composites were characterized by Fourier Transform Infrared (FTIR) spectrophotometer and Thermogravimetric Analyzer (TGA) The samples were cross-linked by electron beam and irradiated at the dosage range of 0-200 kGy and 3.0 MeV. The mechanical properties of the samples which are tensile test and flexural test were measured by universal tensile machine whiles hardness was measured using Rockwell hardness tester. The gel content was performed to determine the formation of crosslinking and it showed improvement with increase dose up to 150 kGy. The result shows the increasing of tensile strength, tensile modulus, and hardness at the dosage 150 kGy but slightly decline at dose up to 200 kGy. Meanwhile TGA test showed that both irradiated and unirradiated samples have same trend characterization but irradiated samples are slightly more thermal stability. As a conclusion the electron beam irradiation enhance mechanical and thermal properties of ethylene vinyl acetate/polyamide 6/high density polyethylene nanocomposite.

Abstract: The influences of tool tilt angle and tool plunge depth on tensile properties of friction stir welded AA 5083-H116 with the thickness of 4 mm were studied. Four different values of tool tilt angle of 1΀ 2°, 3°, and 4° were used to fabricate the joints. The tool plunge depths were choosen 3.85 mm, 3.90 mm and 3.95 mm. The FSW rotational speed and welding speed were 1125 rpm and 30 mm/min, respectively. The temperature, macrostructure, hardness and tensile strength of joints were compared and discussed. Results show that the increase of tool tilt angle and tool plunge depth resulted the welding temperature increase. Due to the increase of welding temperature, the hole defect become smaller. Tensile testing results indicated that the tensile strength of joints increased with increasing both the tool tilt angle and tool plunge depth.

Abstract: This work study the mechanical properties (tensile, flexural and impact) of four different formulation of HDPE/EVA/MMT nanocomposite with present of 1.5 phr compatibilizer as a preliminary study before further development of HDPE/EVA/MMT/EFB nanohybrid biocomposite. The ethylene vinyl acetate (EVA) was varied from 0, 10, 20 and 30 wt%. Meanwhile the nanoclay montmorillonite (MMT) was varied from 0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 phr. HDPE/EVA/MMT ternary blends were prepared by melt extrusion blending technique using a single screw extruder. The result found that in absent of nanoclay MMT, the tensile and flexural properties (strength and modulus) of HDPE/EVA/1.5 phr compatibilizer were decreased as EVA amount are increased. Meanwhile in absent of EVA gave the highest tensile and flexural strength which are 38.53 MPa and 35.02 MPa respectively. However the trend is reciprocal for impact strength. The Izod impact test found that 30 wt% EVA give the highest impact strength which is 103.88 J/m , followed by 20 wt% EVA, 10wt % EVA and 0 wt% EVA which are 59.91 J/m, 38.11 J/m and 30.63 J/m respectively. This is because EVA plays a role as impact modifier. Meanwhile incorporation of nanoclay MMT improved the tensile and flexural properties but reducing the impact properties.