Abdullah Mimaroglu

Influence of Process Parameters on the Mechanical and Foaming Properties of PP Polymer and PP/TALC/EPDM Composites

In this study, PP and Talc/EPDM/PP composite materials are used. Foaming process is achieved by a conventional injection molding method. The influence of injection pressure and melting temperature on the average cell dimension, cell number, skin layer thickness, foam density and mechanical properties of investegated foam materials were evaluated. It is observed that cell density is increased by the increment of injection pressure. However, the values of skin layer thickness, density, cell diameter and charpy impact strength are decreased. In addition, the values of skin layer thickness, cell density, density and impact strength are increased with the increment of melting temperature.

Extension in Shelf Life of Fresh Food Using Nanomaterials Food Packages

In this study, the use of nanocomposite polyethylene films to extend shelf life of food products and to enhance its barrier and mechanical properties was investigated. Nanocomposite was designated 80%wt LLDPE, 14.28%wt PE-g-MA, and 5.72%wt organoclay and package films were prepared on the “cast-film” line. The physical and chemical properties of these films were determined and evaluated. The results showed that an “exfoliated/intercalated” mixture was obtained, with un pronounced change in mechanical properties and transparencies, while oxygen permeability is decreased by 42% and the shelf-lives of foods extended up to twofold.

Tribological performance of industrial polyamide-imide and its composite under different cooling conditions

Abstract Polyamide-imide (PAI) polymer is a high-temperature resistant polymer, which is used as contact breaker material because of its high electrical insulation property. The working conditions of contact breakers arise from the wear and friction problem conditions of these materials. Therefore, the tribological behavior of PAI polymer is important. In this study, the friction and wear performance of pure PAI polymer and PAI composite [PAI+12% graphite+3% polytetrafluoroethylene (PTFE)] were studied in two different cooling environmental conditions (with and without air cooling). Wear tests were carried out with the configuration of a polymer pin, on a rotating AISI 316 L stainless steel disc. Test conditions were atmospheric conditions, 50 N, 100 N, and 150 N loads and 0.5, 1.0, 2.0 and 3.0 m/s sliding speeds. For sliding without air cooling and sliding with air cooling, the results show that the coefficient of friction and wear rates for pure PAI and PAI+12% graphite+3% PTFE composite, slightly decrease and increase with the increase in applied load and sliding speed values, respectively. In addition, for the range of loads and sliding speeds of this study, low coefficients of friction and high specific wear rates are registered at sliding under air cooling conditions. Finally, the wear mechanism includes adhesive and abrasive processes.

Surface Modification of Medium Carbon Steel by Using Electrolytic Plasma Thermocyclic Treatment

In this work, using the electrolytic plasma thermocyclic treatment technique (EPTT), surface modification of medium carbon steel was carried out. The EPTT system was set as industrial scale. Na2CO3 was used as electrolyte in water. Various voltage and ampere values were performed to obtain good surface properties. Moreover, different impulse ratio and cooling rates were performed. Metallographic studies were carried out with an optical microscope, scanning electron microscope (SEM), energy dispersive spectrometer (EDS) to study the hardened and modified surfaces. Also microhardness and Rockwell hardness tests were performed. The reliable microstructure and hardness values were obtained on the surface of steel samples.

Comparison of tribological performance of PEEK, UHMWPE, glass fiber reinforced PTFE and PTFE reinforced PEI composite materials under dry and lubricated conditions

Abstract In this study, the tribological performance of poly-ether-ketone (PEEK), ultrahigh molecular weight polyethylene (UHMWPE), glass fiber reinforced poly-tetra-fluoro-ethylene (PTFE) and PTFE reinforced poly-ether-imide (PEI) composite materials, under dry and lubricated conditions, were compared and evaluated. Wear tests were carried out on a pin-disc arrangement and under 50, 100 and 150 N applied loads and 0.5 m/s sliding speed conditions. The results show that the coefficient of friction and specific wear rates for these materials decreases with the increase in applied load values. Finally, the wear rates for PEEK, UHMWPE polymers, PTFE+20% glass fiber reinforced (GFR) and PEI+10% PTFE composites under dry and lubricated conditions are in the order of 10-14 and 10-15, respectively. The results suggested that it is convenient to use PTFE+20% GFR composites for machine components with low processing and product costs.

Mechanical, electrical and tribological properties of graphite filled polyamide-6 composite materials

Abstract In this study, the influence of adding graphite filler, on the mechanical, electrical and tribological properties of nylon-6 composites, is studied. Graphite fillers with different percentages, varying between 5 and 15 wt% were added to nylon-6 polymer material. Nylon-6 composite samples were prepared by the injection molding process. Tensile, impact, electrical and tribological tests were carried out and the dielectric permittivity tangent loss factor, tensile strength, modulus of elasticity, elongation at break, impact strength, specific wear rate and coefficient of friction properties were obtained. The results showed that the tensile strength, elongation at break, impact strength, and specific wear rate of nylon-6 composites, decrease with the increase in graphite filler weight ratio, while the modulus of elasticity, hardness, real part of dielectric permittivity, imaginary part of dielectric permittivity and dielectric loss, increase with increase in the filler weight ratio. Furthermore, it is observed that a rise in the relaxation time of ionic polarization is proportional to the increase in the amount of graphite in the medium and the dielectric conductivity and loss decrease proportionally after approximately 10 KHz. Finally, the maximum improvement in properties, in total, is recorded following the addition of 5 to 10 wt% graphite filler.

Evaluation of the sliding performance of polyamide, poly-oxy-methylene and their composites

Abstract The friction and wear performance of cast polyamide, unfilled poly-oxy-methylene, 10 wt.% graphite filled polyamide 6, 10 wt.% graphite filled poly-oxy-methylene, and 10 wt.% graphite plus 6% wax filled polyamide 6 sliding against stainless steel under dry sliding conditions were studied. The aim was to evaluate the tribological behavior of the above materials which enables suggesting alternative material for costly cast polyamide polymer in industrial applications. Tribological tests were carried out using a pin-on-disk arrangement at a sliding speed of 0.5–2.0 m s−1 and under applied loads of 50 to 150 N. The results showed that the friction coefficient of the tested materials decreases with the increase in applied load as well as with the decrease in sliding speed values. Furthermore, the lowest wear rate is 2.24−15 m2 N−1 for 10 wt.% graphite filled polyamide 6 composite. This suggests its use instead of cast polyamide polymer. Finally, it is concluded that the wear mechanism includes transfer film and deformation.

Evaluation of morphological characteristics and mechanical performance of Rockforce mineral fiber- and glass fiber-reinforced polyamide-6 composites

Abstract In this study, the effect of addition of Rockforce mineral and glass fiber fillers on the mechanical properties and morphological characteristics of polyamide-6 composites were evaluated and compared. Reinforcements, single and mixed compounds by various weight ratios between 10 and 30 wt%, were added to polyamide-6 polymer. Uniaxial tensile, Izod impact, and flexural tests were carried out. Tensile strength, elongation at break, tensile modulus, flexural strength, flexural modulus, and impact strength were obtained. The results showed that the tensile strength, tensile modulus, flexural strength, and flexural modulus of polyamide-6 composite increased with the increase in the glass fiber ratio and are slightly influenced by the addition of Rockforce mineral fibers. Moreover, the impact strength follows an increasing and decreasing profile, whereas elongation at break values decreased with the increase in reinforcement ratio. Finally, scanning electron microscopy was used for comparison and evaluation of the fracture surface of the polyamide-6 composite.

Robustness of Wheelchairs Under Direct Frontal Impact Loading Conditions

In this study, the robustness of five different commercial type wheelchairs under direct frontal impact loadings were modeled, examined and compared. Wheelchairs were modeled, simulated and analyzed under direct frontal impact process using ANSYS/LS-DYNA software. The stresses, strains and displacements of deformed shapes were obtained and compared. The results showed that, “Wheelchair Chassis 4” is the most economic and robust design. Finally the chosen wheelchair design was modified and developed and its robustness was examined.Copyright

Experimental and theoretical study of the rubbing process of epoxy composites against steel

Abstract In this study, the tribological behavior of epoxy composites was experimentally studied and analytically modeled using finite element techniques. Wear test and modeling were carried out for pin-on-disk configuration and under identical boundary and test conditions. The tribological elements consisted of Al2O3 filled epoxy composite pin and a steel disk. The tribological system was modeled two-dimensionally and a quasi-static analysis was performed. The wear amount and the developed stresses during the rubbing process were predicted and compared with the experimentally determined results. A good correlation between the experimental and analytical results were observed.