Jung-Il Song

Wear properties of Saffil/Al, Saffil/Al2O3/Al and Saffil/SiC/Al hybrid metal matrix composites

Abstract The purpose of this study is to investigate the wear properties of Saffil/Al, Saffil/Al 2 O 3 /Al and Saffil/SiC/Al hybrid metal matrix composites (MMCs) fabricated by squeeze casting method. Wear tests were done on a pin-on-disk friction and wear tester under both dry and lubricated conditions. The wear properties of the three composites were evaluated in many respects. The effects of Saffil fibers, Al 2 O 3 particles and SiC particles on the wear behavior of the composites were elucidated. Wear mechanisms were analyzed by observing the worn surfaces of the composites. The variation of coefficient of friction (COF) during the wear process was recorded by using a computer. Under dry sliding condition, Saffil/SiC/Al showed the best wear resistance under high temperature and high load, while the wear resistances of Saffil/Al and Saffil/Al 2 O 3 /Al were very similar. Under dry sliding condition, the dominant wear mechanism was abrasive wear under mild load and room temperature, and the dominant wear mechanism changed to adhesive wear as load or temperature increased. Molten wear occurred at high temperature. Compared with the dry sliding condition, all three composites showed excellent wear resistance when lubricated by liquid paraffin. Under lubricated condition, Saffil/Al showed the best wear resistance among them, and its COF value was the smallest. The dominant wear mechanism of the composites under lubricated condition was microploughing, but microcracking also occurred to them to different extents.

Fabrication of borassus fruit lignocellulose fiber/PP composites and comparison with jute, sisal and coir fibers.

Novel composites based on borassus fruit fine fiber (BFF) and polypropylene (PP) were fabricated with variable fiber composition (5, 10, 15 and 20 wt%) by injection molding. Maleated PP (MAPP) was also used as compatibilizer at 5 wt% for effective fiber-matrix adhesion. FTIR analysis confirms the evidence of a chemical bonding between the fiber and polymeric matrix through esterification in presence of MAPP. The tensile and flexural properties were found to increase with 15 and 10 wt% fiber loadings respectively, and decreased thereafter. Coir, jute and sisal fiber composites were also fabricated with 15 wt% fiber loading under the same conditions as used for BFF/PP composites. It was found that the mechanical properties of BFF (15 wt%)/PP composites were equivalent to jute/PP, sisal/PP and superior to coir/PP composites. Jute/PP and sisal/PP composites showed higher water absorption than BFF/PP and coir/PP composites. These results have demonstrated that the BFF/PP composites can also be an alternative material for composites applications.

Dry sliding wear behavior of Al2O3 fiber and SiC particle reinforced aluminium based MMCs fabricated by squeeze casting method

Al2O3 fiber (Al2O3f) and SiC particle (SiCp) hybrid metal matrix composites (MMCs) were fabricated by squeeze casting method. The tests were carried out using a pin-on-disk friction and wear tester by sliding these pin specimens at a constant speed of 0.36 m/s (570 r/min) against a steel counter disk at room temperature, 100 °C and 150 °C, respectively. To observe the wear characteristics and investigate the wear mechanism, the morphologies of the worn surfaces and specific wear rate were analyzed by using scanning electron microscope (SEM) and Arrhenius plots. Moreover, the effects of fiber orientation and hybrid ratio were discussed.

Mechanical and thermal properties of epoxy composites reinforced with waste peanut shell powder as a bio-filler

Bio-filled polymer composites are gradually replacing plastics to achieve the aim of environmental sustainability. Present study has been carried out to prepare the composites made by reinforcing waste peanut shell powder (PSP) as a natural filler into epoxy resin matrix. The natural filler extracted by manual process was subjected to alkali treatment with the concentrations of 2, 5 and 7 w/v%. The composites fabricated by varying the weight fractions of filler in the range of 5 to 15 wt%. The effects of bio-filler content of the composites on tensile and thermal properties were evaluated by Fourier transmission infrared spectroscopy (FTIR), universal testing machine, scanning electron microscope (SEM) and thermal gravimetric analysis (TGA). The studies reveal that the tensile strength and tensile modulus increased with the increasing of bio-filler content. The highest mechanical properties of 7 % alkali treated PSP loaded Epoxy composite were achieved at biofiller mass content of 15 wt.%. The morphology of the composites shows better bonding between the filler and resin, thus leading to improvement of the mechanical properties. The TGA results revealed that the polymer composites showed thermal resistance on increasing NaOH concentration and filler content.

Improved flame-retardant and tensile properties of thermoplastic starch/flax fabric green composites

This article highlights the development of biodegradable flame-retardant composites using a compression technique on low-cost starch, flax fabric (FF) and ammonium polyphosphate (APP) raw materials. The starch was plasticized into thermoplastic starch through a mechano-ball milling process and composites were developed by reinforcing the FF and incorporating varying amounts of APP. The effects of APP on the flammability and thermal properties of the composites were studied. Limited oxygen index and horizontal-burning tests exhibited significant sustainability of the composites toward flame and direct flame self-extinguishment. It was observed that at higher temperatures, APP leads to formation of thermally stable char. The flame retardant properties of the composites were speculated to be due to the protective compact crosslinked network (POP and POC) of the char. The reported effects of APP include improvement in mechanical and biodegradation properties. This investigation provides the design of novel flame-retardant green composites with excellent properties.

Effect of Ultrasonic Nanocrytalline Surface Modification on the Microstructural Evolution of Inconel 690 Alloy

Specimens of Inconel 690 were investigated after ultrasonic nanocrystalline surface modification (UNSM) using microhardness tests, electron backscattered diffraction, and transmission electron microscopy (TEM). After UNSM treatment, a 60% increase of hardness up to ∼310 µm in depth was observed. Layer-by-layer TEM analysis showed well-refined grains and twins in addition to the high dislocations density. The mechanism of the microstructure refinement was attributed to the development of nano-grains, twin structures, and dislocations.

Thickness dependent properties of diamond-like carbon coatings by filtered cathodic vacuum arc deposition

Abstract Diamond-like carbon (DLC) coatings of 300, 500 and 650 nm thickness were deposited on stainless steel substrates using a filtered cathodic vacuum arc hybrid with magnetron sputtering system. A 100 nm thick chromium interlayer was deposited before the deposition of the DLC coatings. The films morphology was characterised by field emission scanning electron microscopy and structure was identified by Raman spectroscopy. Tribology was evaluated by ball disc wear test and wear tracks were observed by scanning electron microscopy. The interface adhesion was studied by scratch tester. The results of all characterisations were concluded and 500 nm DLC coating has suggested as optimum thickness that would be applicable for industrial applications.

Effect of concentration of ATH on mechanical properties of polypropylene/aluminium trihydrate (PP/ATH) composite

Aluminium trihydrate (ATH) is being extensively added to polypropylene (PP) to make a fire retardant composite. Blends of PP/ATH composite are more fire resistant as compared to pure PP. Percentage proportion of both the constituents in the final composite depends upon the application. Improvement in the fire retardant properties of such composites have been studied and published in literature but effects on mechanical strength have not been addressed. The effect of concentration of ATH on the strength of PP/ATH composite was presented. The tensile, flexural and fracture properties were studied and discussed. Experimental tests, ASTM analytical formulae and finite element approach were used. It has been found that increase in ATH has an inverse effect on the mechanical strength.

Microstructural Characterization of SS304 upon Various Shot Peening Treatments

In the majority of cases, material failure initiates from the surface because of fatigue, creep, wear, corrosion, etc. Thus, optimizing the surface microstructure enhances the general behavior of a material in terms of fatigue life, friction, wear, corrosion and even tomography, and also its lifetime. Thanks to intensive and extensive studies on nanostructured metals in the past several decades, the beneficial effects of optimizing nanostructure of metals and alloys have become more and more obvious (Gleiter, 2000; Meyers et al., 2006), e.g., ultra-high hardness and strength (Liu et al., 2013), enhanced physical properties (Lu et al., 2004), enhanced corrosion resistance (Lee et al., 2009). Fabrication of a nanostructure on the surface of a bulk metal can involve either coating it with a dense, hard film creating a surface alloy, or inducing a phase transformation via plastic deformation such as a strain induced surface grain refinement (Mayer et al., 2012), or also nano crystallization (Lu & Lu, 2004; Zhong et al., 2010). Of course, even the combination of the methods can be used for some specific applications (Du et al., 2009; Hong et al., 2011). Shot peening technologies have been used for a long time and are proven to be an effective method for introducing severe plastic deformation to the surface region, thereby refining and possibly nanocrystallizing the surface microstructure (Tong et al., 2003; Umemoto et al., 2003; Suh et al., 2007). One such method, air blast shot peening (ABSP), utilizes hard balls (tungsten carbide) for the energy transfer from compressed air to the surface of the work pieces. ABSP is a very flexible technology and is normally used in a cast factory to clear and strengthen the surface of the castings. However, little is known

Optimization of process parameters for electrophoretic deposition in CNTs/carbon fiber hybrid composites

Carbon nanotubes (CNTs) have attracted a great deal of interest in the development of high-performance engineering composites, due to their exceptional physical, mechanical, electronic and thermal properties. Incorporation of CNTs into polymer has shown great improvements in the functional property, however, the enhancement of the mechanical property was insignificant compared with that of micro-sized fiber reinforced polymers. In order to realize the application of composites for structural and multifunctional parts, it is necessary to develop hybrid composites with micro- and nano-sized reinforcements. CNT reinforced hybrid composites have been studied in several ways: the addition of CNTs to a matrix with various dispersion methods, the growth of CNTs on substrate reinforcements, CNT sprays, etc. In this study, the electrophoresis deposition (EPD) method has been applied to deposit CNTs on a carbon fabric. By applying an electric field between a copper plate and a substrate, the negatively charged CNTs in a suspension move toward a carbon fabric. The controllable parameters in the EPD process are identified as the deposition time, the voltage, the contents of the CNTs, and the distance between the copper plate and the carbon fabric. In order to determine the optimal process conditions, the Taguchi method for the statistical design of experiment (DOE) has been utilized. Since the interlaminar shear strength (ILSS) of the hybrid composites is associated with the amount and the degree of distribution of the CNTs, it was selected as the response for the analysis of means (ANOM) and signal to noise (S/N) ratio. The ILSS was measured by short-beam test according