جستجوی مقالات مرتبط با کلیدواژه "رشته پیچی" در نشریات گروه "فنی و مهندسی"

Flanges are parts that provide the possibility of connection, change of direction, access for repairs and inspection between large and main parts of equipment and structures. In this research, due to the importance of maximum lightening while maintaining the strength of parts in aerospace structures, composite flanges and shells were made, which are used in aeronautical structures such as bossting rockets and satellite carriers. They are responsible for connecting the parts and large shells of the structure. The material of the flanges used in these structures is aluminum in the lightest state, and in this research, with the aim of lightening as much as possible, 4 flanges and 4 shells were made in 2 sets, each set includes 2 flanges and 2 shells. After connecting the flanges and shells to each other, experimental modal analysis and tensile tests were performed. Also numerical simulation of the modal and tensile test was performed with ANSYS software. The results of experimental tests and numerical analysis on the manufactured parts show that the specific frequency of the composite flange is higher than that of the steel and aluminum flange (in low frequency range). Also, the delamination factor in the composite flange blade has more effect on increasing the length of the structure due to the tensile force, rather than the failure of the matrix and fibers.

The filament winding process is one of the most important and widely used processes in the manufacture of composite structures in order to achieve high strength and rigidity. In this process, there are important parameters such as fiber tension, how the fibers are twisted, the effect of layering, twisting angle, twisting pattern of fibers, materials, etc. which can play a significant role in this process. In this regard, the twisting pattern has been less studied by researchers than other parameters. In this research, the effect of fiber twisting pattern on the hydrostatic pressure threshold of epoxy glass cylinder has been investigated. For this purpose, glass/epoxy cylinders with 4 different twisting patterns were made with ± 54 arrangement and subjected to hydrostatic test with internal pressures of 5-50 bar, where the amount of radial displacement in the middle of the cylinder was measured experimentally. In the following, the radial displacement of cylinders due to the internal pressure was also modeled using numerical analysis (Abaqus) and compared with experimental results. In order to validate the experimental and numerical results, theoretical model was used and the results were compared. All of the results obtained were in acceptable limits and showed that the pattern having finer texture has a higher compressive strength. Also, the simulation results showed a good agreement with the experimental results.

Due to unique properties, lattice composite shells are used extensively in aviation, marine and automotive industry. The aim of this research is experimental and numerical free vibration analysis of composite sandwich cylindrical shells with lozenge cores. For the fabrication of this shells, silicone mold, filament winding, and hand lay-up method were used. Stiffened shells and simple shells are fabricated, separately. Then, composite sandwich cylindrical shells with lozenge cores were created by attaching the two parts together. The modal test is done on the shells and natural frequencies have been extracted. The comparison of experimental results and, numerical results obtained from Abaqus showed that there is a good agreement between them. By using Taguchi method, a parametric study was performed on the vibrational behavior of sandwich shells with lozenge cores via six parameters that such as stiffeners’ pair number, stiffener thickness, unit cell number, skin thickness, layers sequence and boundary condition. The results show that the natural frequency has a most sensitive to the boundary condition, skin thickness and least sensitive to stiffener thickness, layers sequence. To evaluate the efficiency of a sandwich shell, the natural frequency of sandwich shell are compared with simple shell in the different boundary condition. The results show that the natural frequency of sandwich shell with lozenge core is 176% and 34% higher than an equivalent simple shell at free and clamp boundary condition, respectively.

Braided and filament-wound tubular composites were produced by various glass fiber preform structures on a cylindrical mandrel using a modified maypole braiding machine. The composites were then impregnated with unsaturated polyester resin by vacuum infusion process (VIP). After performing compression test on the samples and calculating the failure force and failure energy، it was observed that the filament-wound sample displayed higher compression properties than those of braided samples with the same fiber volume percent. This was due to having more reinforcing layers with more reinforcing strands for compensating the effect of waviness in its braided counterpart. The results showed that the braided samples، with the same number of layers with the filament-wound tubes but different fiber volume percentage، show the highest compression failure force and energy. The reason for this phenomenon was attributed to higher tube wall thickness in the braided sample and consequently more stable behavior during compression loading.

Composite CNG tanks have a number of advantages such as high gas pressure، safer failure modes، higher mechanical properties، higher corrosion resistance، as well as being 2 to 4 times lighter than steel tanks. The main aim of this work is the thermo-mechanical analysis and evaluation of Type III composite CNG tanks. A high-performance hot-cure Araldite epoxy resin system was selected and modified as the matrix. The T-700S high-strength carbon fiber was also selected as the reinforcement. After determining the various attributes of these two principal constituents، the properties of the lamina were calculated by the micromechanical approach. A 5-axis filament winder machine was constructed in this research to manufacture the CNG tank. 3D thermo-mechanical analysis was conducted by ANSYS-12 based on the micromechanical outputs for 50، 55 and 60 percent of fiber volume fractions. Results showed that increasing the number of layers and the fiber volume fraction have opposite effects on the behavior of laminate and the metal liner failure. It wasalso found the significant effects of thermal stresses on the laminate failure; while their effects were ignorable on the metal liner failure.