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Showing 3 results for Mohammadian Semnani
Volume 5, Issue 3 (Fall 2021)
Abstract
Abstract
Research subject: In this research, epoxy modification was successfully performed by polyurethane and its effect on abrasion and adhesion properties have been investigated. The most important concern in the blending of these polymers was the formation of gels upon exposure of epoxy resin and isocyanate in polyurethane.
Research approach: One solution to overcome this problem is to control the chemical activity of Isocyanate. Therefore to reduce the chemical activity of isocyanate and prevent gel formation due to the combination of epoxy and polyurethane, first polyurethane prepolymer containing 3.58 wt.% NCO was prepared by mixing poly tetra methylene glycol 2000 (PTMG 2000) and toluene di isocyanate (2,4-TDI); and then by adding 20 wt.% of it to the epoxy resin, the curing process was completed by using dimethyl thio-toluene di amine (DMTDA) as a common curing agent and also specific heat treatment.
Main results: Fourier transformation infrared spectroscopy results showed that the modification process has been successful by elimination of the peaks related to epoxide and isocyanate groups in the prepared sample in addition to the formation of a broad peak related to secondary hydroxyl group (C-O) due to the opening of epoxide rings. Pull off tests also confirmed increasing adhesion to carbon steel substrate as a result of secondary hydroxyl generation through this blending. Although, the Persoz hardness of modified epoxy decreased by 5%, but with a 17-fold reduction of elastic modulus (as per tensile test result), abrasion resistance improved 6 times according to abrasion test. Finally, joining of the cavities to each other is introduced as the abrasion mechanism by considering the field emission- scanning electron microscope images.
Volume 20, Issue 9 (September 2020)
Abstract
This research is mainly focused on to study microstructure and mechanical properties of AA5051 aluminum alloy deformed by equal-channel angular pressing (ECAP) process at 200˚C and in BC routes and 4 four passes. The ECAP processing was carried out using die with an intersecting channel angle ‘ϕ’= 120° and corner angle ‘Ψ’= 20°. The results of uniaxial tensile test showed that tensile strength was found to be increased from 115MPa for annealed sample to 239MPa after four passes ECAP in route BC that shows that the strength in ECAP samples has increased. In addition, the percentage of elongation also decreased in initially passes and then increased slowly. Microstructure and grain refinement of specimens were investigated by optical microscopy and scanning electron microscopy and fractography were investigated by scanning electron microscopy. The grain size of annealed sample was 123μm and decreased to 18μm after four passes ECAP in route BC. The hardness also increased from 51HV in annealed sample to 90HV the fourth passes.
Volume 21, Issue 6 (June 2021)
Abstract
The aim of this study is to improve the strength properties of glass-aluminum multilayer hybrid composite using AA1050 aluminum sheets processed by the accumulative roll bonding (ARB) process. Also, the effect of different cycles of ARB process on the strength properties of hybrid composite has also been investigated. At first, the ARB process was applied on the AA1050 sheet. Afterwards, the microstructure and tensile properties of the ARB deformed sheets were investigated. Then, the ARB processed AA1050 sheets were used to make glass reinforced aluminum laminate (GLARE). In the end, the tensile properties of the GLARE composite were examined. By the progress of the ARB process, the hardness and strength of the sheet increased. The elongation of the first cycle processed specimens dropped drastically. But, by increasing the process cycles, the elongation increased gradually. The use of the ARB processed aluminum sheet in the manufacture of GLARE composite significantly improved the tensile strength of the GLARE. In the GLARE made of annealed aluminum, most of the elongation of the aluminum layer occurred after the breaking of the glass fibers and in conditions outside the GLARE composite; as a result, the reduction of the sheet elongation during the ARB process caused the simultaneous failure of the metal layers and the glass fibers during the tensile test of the GLARE. Hence, this event did not reduce the ductility of the composite. In other words, the total energy absorption and fracture toughness of the aluminum layers occurred when the GLARE had not failed.
