نشریه علوم و فناوری کامپوزیت
سال نهم شماره 3 (پیاپی 33، پاییز 1401)

In recent decades, the use of nanoparticles in composite structures and composite sandwich panels has expanded due to the achievement of mechanical and physical properties. In the present study, the effect of graphene nanoparticles on the strength of a sandwich panel structure with a new vein geometry model under quasi-static loading and low-velocity impact has been investigated. The vein structures are made of glass/epoxy layers with different percentages of 0.0, 0.1, 0.3 and 0.5% of graphene nanoparticles. In addition, polyurethane foam was used in the center of the sandwich vein structure. In order to check the damage inside the vein structure, cut-out images of the damage have been prepared and the results have been reported. In addition, FE-SEM analysis was used to investigate the microstructure and evaluate the distribution of graphene nanoparticles in the polymer structure. The characteristics of crashworthiness in the tested samples were discussed. It was concluded that this type of sandwich vein structure with polyurethane foam core can limit the propagation of the damage in quasi-static loading and drop weight test and keep the sandwich structure healthy. On the other hand, as a result of the impact, several different failure modes have occurred, including fiber failure, matrix cracking, delamination, Foam detachment, foam failure, and foam crushing. After the FE-SEM analysis, it was observed that the sandwich structure with 0.3% of nanoparticles has a higher density than the other tested structures

In this research, Al-Al2O3 composite coating was created using cold spraying process on Al-1050 alloy sheet. In order to create the coating, pure aluminum powder and Al2O3 powder were mixed with equal weight percentage (50% wt.). The coating was done using nitrogen gas at a temperature of 300 ℃ and a pressure of 30 bar and a spraying distance of 20 mm. Moreover, the coating was shot peened using a centrifugal process with a speed of 3000 rpm and peen size of 0.6 mm for 3 minutes. The effect of the shot peening process on the properties and quality of the coating was investigated. The characteristics of the coating were investigated using microhardness measurement, scanning electron microscope, Clemex image analysis software, and atomic force microscope. The results show that the hardness of the coating increases by 10% due to the shot peening process on the composite coating and the porosity of the coating decreases by 80% due to the shot peening process. The results of the atomic force microscope show that the surface roughness increases due to the shot peening process, and on the other hand, the coating thickness decreases due to condensation and wear.

The aim of this study was manufacturing and evaluation of the mechanical and physical (water absorption) of a green geopolymer composite reinforced with kenaf fibers and carbon nanotubes. For this purpose, the effect of amount of kenaf fibers, carbon nanotubes and water each in 5 levels (% wt) compared to metakaolin-based geopolymer and steel slag on the mechanical and physical properties of the composite were evaluated. Response surface method and central composite design were used as statistical method to select the mixtures. Bending tests (bending strength, modulus of elasticity and fracture toughness), compression test and water absorption were conducted on the samples. Also, ultrastructure of geopolymer and dispersion quality of carbon nanotubes and kenaf fibers in the composite matrix, was evaluated by FESEM images. The results showed that by increasing the amount of kenaf fibers up to 7.5%, the bending strength, compressive strength, fracture toughness and water absorption increased, whilst at higher amounts of the fibers, the values of mechanical strength decreased. Also, the use of carbon nanotube as a reinforcement up to 0.6%, had a positive effe on increasing the mechanical strengths of the composite. The results of FESEM showed that with increasing the amount of percentage of kenaf fibers, and carbon nanotubes the diameters of pores in matarix highly increased. Generally, in this research accoriding to the statistical results, the sample with the combination of 7.5% kenaf fiber, 0.6% carbon nanotube and 29% water is introduced as the optimal combination.

The use of nanoparticles in the hyperthermia method is very effective due to their small size to penetrate the cancer cell and better control and uniform temperature distribution. Cobalt nanoparticles are a good option in hyperthermia due to their saturated momentum and excellent magnetic properties. On the other hand, to minimize the cytotoxicity of cobalt nanoparticles and improve hyperthermia, it is necessary to use cobalt nanoparticles in composite form with other materials. For this purpose, in the present study, reduced cobalt-reduced cobalt (rGO-Co) composite nanoparticles were synthesized for use in heat treatment by the co-precipitation method. The synthesized powders were characterized by FESEM, TEM, XRD, VSM, and DSC-TGA tests, and the MTT test was used to determine biocompatibility, and hyperthermia test was used to determine the specific adsorption rate of the material. The results of the hyperthermia test showed a higher specific adsorption rate of rGO-Co composite nanoparticles than graphene oxide and cobalt nanoparticles. The study of the biological behavior of rGO-Co composite nanoparticles at concentrations of 30-100 μg/ml showed good biocompatibility of rGO-Co composite nanoparticles in comparison with cobalt nanoparticles. Fibroblasts grew and proliferated well at concentrations of 30 and 50 μg/ml.

In this paper, first, the process of modeling the delamination due to the traditional drilling process with twist bit in composite laminates in the finite element bed has been described and the drilling results in a laminate have been investigated. Then, the mechanical behavior of this laminate containing the delamination was studied under uniaxial loading and the results of the analysis were compared with the literature. For this analysis, the mechanical and strength properties and behavior of the composite layers were assigned by writing the structural laws of anisotropic materials and the Hashin damage criterion, respectively, in the form of VUMAT subroutine in ABAQUS software. To monitor the delamination phenomenon, cohesive elements between the layers were used based on the bilinear traction-separation law. There was a good agreement between the results of the present finite element analysis and the previous researches. In the following, the behavior of drilled composite laminate containing primary drilling-induced delamination under tensile and compressive loads was investigated. The results show that in the case where the initial delamination was applied around the hole, the tensile and compressive strength of the laminate decrease by 5.5 and 19.5 percent on average, respectively, compared to the case where the drilled plate was analyzed regardless of the initial delamination. The larger the delamination area, the greater the strength drop

Epoxy resins are widely used as coating to protect metals in various applications. The properties such as very good processability, excellent chemical resistance, good insulation against electricity, and strong adhesion to non-homogeneous materials have caused epoxy materials to be widely considered in the coating industries. Epoxy coatings are susceptible to damage such as microcracking. These types of damages cause defects in the coating and reduce the appearance (beauty) and mechanical strength of the coating. Also, the penetration of water, oxygen and corrosive agents to the surface of the metal is accelerated. As a result, the local corrosion occurs in the metal. The repair process of polymer coatings is time-consuming, expensive, and in many cases it is impossible to detect the damages and access them for repair. Therefore, it is very important to find a solution to automatically repair the microcracks without any type of human intervention and the replacement of new components. Therefore, this can be possible by designing self-healing intelligent systems. The most common method of preparing self-healing coatings is microencapsulation of healing agent in polymer or mineral shells and embedding the prepared microcapsules in the epoxy matrix. The self-healing properties of the epoxy coatings can be investigated with electrical impedance spectroscopy and salt spray tests. In this research, the studies on self-healing epoxy coatings have been reviewed.