Composite shells are widely used in various industries due to their low weight and high strength. Designing these structures involves various engineering analyses, and one of the most important studies is the investigation of the buckling of shells under axial load. The aim of this research is to investigate the vibrational correlation method on composite cylinders with delamination defects. Delamination defects can occur in structures under different conditions and have a significant impact on the strength of the cylinder. Therefore, in this study, different dimensions and quantities of delamination defects in various specimens were examined using the vibrational correlation method. Carbon fibers of type T300 were used as the reinforcement material, and the epoxy resin LY556 was used as the matrix. The hardener and accelerator combined with the resin in this research are HY917 and DY70, respectively. The layer stacking in the specimens was done with angles [55 90 90 55] using the FILAMENT WINDING method, and artificial delamination defects were created between layers 2 and 3 using Teflon sheets. The manufactured specimens were subjected to modal testing under various compressive forces, and then the critical buckling load of the specimens was obtained using the modal testing method. Using numerical modeling software, critical buckling loads and natural frequencies were calculated for various axial compressive loads through linear and nonlinear analysis. These numerical results were compared with experimental results. The vibrational correlation method accurately predicted the critical buckling load in defect-free specimens with a 3% error, but its accuracy was significantly

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, fiber twisting pattern of fibers, type of material suitable for twisting, etc., which can play a significant role in this the strength of the processstructure. In this regard, the twisting pattern has been less studied by researchers less 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, first, glass/epoxy cylinders with 4 four 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 amount of radial displacement of cylinders due to the internal pressure was is 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 twist pattern having with finer texture has a higher compressive strength. Also, the simulation results showed a good agreement with the experimental results.

To study the energy absorption features in composite structures, it is necessary to identify the functional mechanisms and determine the impact of each on the energy absorption. In this study, the behavior of composite tubes under compressive axial load was investigated by acoustic emission monitoring. To make a FILAMENT wound composite tube, the optimal parameters were first determined using literature. In determining the optimal parameters, due to the uncertainty effect of fiber angles, from the intermediate range, the angle of 35 degrees was selected. Then, to ensure the experimental results, the finite element simulation method and the use of the VUMAT subroutine based on the 3D Hashin criterion were used. The results showed that the dominant failure mode was a local shear failure and lateral damage, which first caused the plastic deformation of the sample and then caused the growth of cracks in the fiber direction. Also, the highest percentage of failure mechanisms are matrix cracking, fiber breakage, and separation of fibers from the matrix, respectively. Finally, the use of the developed subroutine to predict the behavior of the structure was useful and was able to predict the behavior of the composite tube even after the maximum crushing force.

Due to the extensive use of composite materials in various industries, recognizing the failure models of these materials is very important. In this article, the behavior and failure models of composite pipes made by FILAMENT-wound with fiberglass, with internal liner and silica nanoparticles under local impact tested and examined. FILAMENT WINDING is performed using a semi-automatic FILAMENT-wound device. Nano particles of silica that are used in the manufacturing the samples during the process of mixing and for better homogenization, the ultrasound is used. The FILAMENT WINDING angle of all 16 tubes was ±55. Impact test, using a gas gun with speeds of 118, 113, 108 and 100 meters per second is done. Add silica nanoparticles increases the elastic modulus and strength of the matrix. However, the existence of brittle liner, the composite shell behavior puts under its effect. In all tests, penetration of the projectile into the tube were occurred. The failure area due to impact, were same to the diameter of the projectile. Rupture of fibers failures in the matrix is the most important models of failure that were observed in impacted composite tubes. The experimental observation were reported, discussed and commented upon.

In this study, the analysis, manufacturing and experimental buckling test of a composite warhead subjected to external pressure and axial load are investigated. Variation of angle and thickness along the none length are obtained, also the optimum FILAMENT WINDING design is achieved by considering minimum disordered patterns and wasting materials. In continue the static and buckling analysis of the composite warhead is performed using FEM software with Eigen value Analysis. The variation of the wound angle and the thickness are surveyed and the optimum angle is extracted. The composite warhead is manufactured based on the optimum angle. The process and equipments of the external pressure test are designed and the composite warhead is tested. The obtained buckling results of the FEM and the experimental are compared and also the efficiency of this method in prediction of buckling behavior of the composite warhead is demonstrated.

Hydrogen has become an attractive source of energy for transportation industry, which is adaptable to the environment. Using composite pressure vessel type IV for storing compressed hydrogen gas seems to be a safety solution because of their ratio of strength to weight. Type IV composite pressure vessels consist of three main parts of polymeric liner, metallic boss and carbon fiber/epoxy composite shell. In the dome zones of these vessels, the thickness of composite layers and the fiber angle would increase because of accumulation of resin and reduction in radius. This issue is caused the modeling of these vessels to be a serious challenge. The WCM plug-in is presented for simulation of axisymmetric or three-dimensional composite pressure vessels type III and IV in ABAQUS software. In addition to the parameters like layer thicknesses and fiber angles, manufacturing parameters such as bandwidth, transition angle and end fraction could be also defined in this plug-in in order to achieve more accurate results. In this study, a type IV high pressure composite vessel with inner volume of two liters is modeled using the WCM plug-in in ABAQUS software. Numerical results are assessed by the available experimental results in the literature. Moreover, failure pressure of this vessel has been estimated by calculating the on-axis stresses and using failure criteria such as Tsai-Hill, Tsai-Wu and Hashin which is not done in other investigations.

Nowadays, multi-WINDING transformers are widely used in power systems, especially in traction networks and steel producing companies. The multi-WINDING transformers have special geometry. They encounter with serious problems and difficulties in design procedure in comparison with conventional two-WINDING transformers. Considering the importance of WINDINGs losses (and the generated heat), the current research firstly focuses on thermal calculations in this type of transformers, also introduces a semi-numerical technique for electromagnetic analysis of split-WINDING traction system transformer. Combining finite element and analytical methods, the WINDINGs losses distribution due to eddy currents is calculated and the modeling results are validated using the experimental results. As shown, the introduced semi-numerical method is a powerful technique for electromagnetic modeling and WINDING losses calculations in split-WINDING transformers. Also, the WINDING losses of the split-WINDING transformer are discussed and compared to the conventional two-WINDING transformer results. Finally, the relation between the WINDING losses and frequency is studied in this paper.

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.