نشریه علوم و فناوری کامپوزیت
سال یازدهم شماره 3 (پیاپی 41، پاییز 1403)

The Purpose of this study is fabrication aluminum matrix composites reinforced with TiB2 in situ ceramic particles by the stir casting process. So, produce composites with 2%, 4% and 6 wt% and contrast with AA5083 alloy of reinforcing particles without. In this study, in order to impurities and surface contamination cleanse and also water molecules contained in the powders of TiO2 and B2O3, preheating operation performed on them. Then milling operation done with speed 750 Rpm for 15 hours, in order to mechanical activation and prevent performed of adverse reactions between the powders in during the casting process. After preparing the powders, they are stoichiometric determined ratio to achieve values of 2%, 4% and 6wt% TiB2 phase were added to the AA5083 alloy molten and after stirring for 15 minutes with speed 350 Rpm, the casting was performed. At the end of in order to properties improve of casting specimens from used hot extrusion process. Then, using phase analysis (XRD), microstructure analysis (OM and SEM) and tensile, hardness and density tests, production or non-production, distribution of reinforcing particles and mechanical properties investigated of samples. The ultimate goal of this research is, using a combined method to problems solve of cast aluminum matrix composites and improving their properties. The results showed an improvement in mechanical properties of samples with increasing reinforcing particles up to 4wt% after completion treatment. As the highest tensile strength and hardness obtained at cast and extruded sample (at temperature of 330 ° C) AA5083/4% TiB2.

Today, composite materials are widely used in various industries due to their unique properties. In the meantime, considering the special application of thermoplastic composites, especially in the aerospace industry, the mechanical properties and fracture behavior of these materials should be evaluated. One of the important processes in the production of thermoplastic composite parts is the HOT PRESS production process. Considering the high durability of these materials and the type of place of use, in addition to examining the mechanical properties, the failure and fatigue life of these materials should also be examined. In this paper, the main goal is to investigate the mechanical properties and failure behavior of the mixed mode (I/II) in the Glass/PP continuous fibers composite. For this purpose, Glass/PP continuous fiber composite was made by HOT PRESSING method. Then, using experimental methods, the composite mode failure behavior (I/II) of this material was evaluated using the fabricated MMB fixture. Finally, the experimental and analytical values of stress intensity coefficients and fracture energy in the mixed mode (I/II) will be reported.

Cycloaliphatic structure in epoxy resins can improve chemical, physical, mechanical and electrical properties. In order to investigate this issue, two cycloaliphatic epoxy resins, (bi-functional) and (tri-functional) were used and then their properties were investigated and compared with DGEBA epoxy resin which has an aromatic structure. All three resins were cured with m-Phenylenediamine and the properties of the cured resins were analyzed by DSC, DMTA and three-point bending analysis. According to the obtained results, the strength and flexural modulus and ILSS of the DGEBA sample were 60, 2600 and 116 MPa, respectively. Bi-functional cycloaliphatic epoxy resin has a limited increase in properties (59, 3700 and 123 MPa) due to the hydrogen bonds of ester groups, and the cycloaliphatic structure hanging in the network does not contribute much to the increase in properties. Meanwhile, the tri-functional epoxy resin, in addition to the role of hydrogen bonds of ester groups, has unique properties due to the correct placement of the cycloaliphatic structure in the cured network and the higher crosslinking density. If the cycloaliphatic structure is placed in polymer network with four links, through the change of conformation between the boat and chair forms or by stretching it, it dissipates the external energy entered into system and by increasing the fracture energy, it prevents the brittle fracture of cured resin. The strength, flexural modulus and ILSS of tri-functional cycloaliphatic resin were obtained as 82, 4300 and 173 MPa, respectively, which shows improvement of about 35, 70 and 50% compared to DGEBA epoxy resin.

This study introduces an innovative approach to the design of honeycomb structures by presenting a new reinforced structure with hexagonal spring-reinforced cell walls. The crashworthiness and energy absorption capabilities of the proposed structure are evaluated and compared to those of traditional honeycomb structures. Additionally, the impact of filling the void space between the cells of the honeycomb structure with rigid polyurethane foam on the mechanical strength and energy absorption of the structures is investigated. In this research, four types of honeycomb structures made of polylactic acid (PLA+) were fabricated using an FDM 3D printer with cubic dimensions. Subsequently, a two-part polyurethane foam was injected into the void space between the cells. The samples were then subjected to quasi-static compressive loading out-of-plane, and the resulting force-displacement diagrams were extracted. The results showed that the proposed spring-reinforced honeycomb structure, in its empty state, exhibited a 14% increase in energy absorption and mean crushing force, along with a 24% increase in crushing force efficiency compared to the traditional honeycomb structure. When filled with foam, the proposed structure showed a 21% increase in energy absorption and mean crushing force and a 26% increase in crushing force efficiency, indicating an improved performance. Furthermore, applying polyurethane foam in both traditional and reinforced honeycomb structures resulted in a 16% and 23% increase in energy absorption and mean crushing force, respectively, demonstrating an improvement in their mechanical properties.

In the present study, the effect of bath temperature (30, 35, and 40°C) on the microstructure and corrosion behavior of the Zn-Co-Al2O3 composite coating deposited on St37 steel substrate was investigated. The microstructure and corrosion behavior of the coating were studied by changing the bath temperature during electroplating. The coatings were deposited at 30, 35, and 40°C. The microstructure and surface morphology of the samples were investigated by scanning electron microscopy (SEM). Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were performed in a 3.5 wt% NaCl aqueous solution to investigate the corrosion resistance of the uncoated and coated samples. The microstructural examination of the coatings revealed that the coating formed at 40°C had more cohesion and uniformity than the other coatings. Furthermore, the percentage of Al2O3 particles in the coating was maximum at this temperature. The positive effect of the coating on enhancing the corrosion resistance of the steel was more pronounced for the coating formed at 40°C compared to the others. In this case, the polarization resistance obtained from the potentiodynamic polarization test was the highest, while the corrosion current density was the lowest for this coating compared to the others. The lower capacitance of the coating formed at 40°C compared to the other coatings in the electrochemical impedance spectroscopy test also confirmed the higher corrosion resistance of this coating.

In this work, Phthalonitrile resin based on bisphenol A was synthesized with a yield of 93% and a purity of 98.91%, and its structure was identified using various techniques. To investigate the effect of curing agent type on curing temperature and thermal property of resin, the synthesized resin was cured with two different curing agents including bisphenole A and methylene dianiline. It was observed that the amine curing agent, despite its lower weight percentage, has a more significant effect on accelerating the curing process. Finally, a composite of the synthesized phthalonitrile resin and carbon fibers was prepared with two resin contents, 32% and 41%, and its mechanical and thermal properties were evaluated. The results indicated that the composite with 32% resin content exhibited superior properties, with an interlaminar shear strength (ILSS) of 36.4 MPa and a modulus of 14.56 GPa. The thermal resistance of both resin and composite was assessed using the TGA technique, revealing that the pure resin has a char yield of 72%, while the composite with 32% resin content has a char yield of 87% at 800°C under a nitrogen atmosphere. Moreover, the TGA results demonstrated that the phthalonitrile / carbon fiber composites has approximately the same thermal stability at air and argon atomosphere, domenstrating excellent ability of this resin as a thermal barrier.