The vibration and stability of axially loaded sandwich cylindrical shells with the functionally graded (FG) core with and without shear stresses and rotary inertia resting Pasternak foundation are investigated. The dynamic stability is derived based on the first order shear deformation theory (FSDT) including shear stresses. The axial load and dimensionless fundamental frequency for FG sandwich shell with shear stresses and rotary inertia and resting on the Pasternak foundation. Finally, the influences of variations of FG core, elastic foundations, shear stresses and rotary inertia on the fundamental frequencies and critical axial loads are investigated
Polymer composites have a wide share among engineering materials. It is important that the material properties are known before being used in industrial applications. Damage behavior needs to be determined in order to safely forming of laminated composites. Propagation characteristics of existing cracks for determining damage are among the current research topics of the researchers. In this study, the fracture toughness of the composite structure was investigated by performing compact tensile and compact compression tests for hybrid fiber reinforced polypropylene composite laminates which have three types of composition having various thicknesses and fiber contents, woven and/or chopped glass fiber reinforcement. The critical energy release rates of fiber and matrix in both tensile and compressive fracture cases were determined in pre-cracked specimens under plane-strain loading conditions. The damage mechanisms of the composite materials used in the present study were described as fiber breakage/buckling of longitudinal and matrix crack/crushing of transverse. As a result of the longitudinal tension, the damage progressed gradually as translaminar fiber breaking in materials containing continuous fibers. In the transverse tension process, fiber-matrix separation caused 2 intralaminar deformation in the materials. The highest fracture critical energy release rate was found in the material with the maximal fiber layer.
It is known that the use of renewable energy has an increasing trend in whole world. Wind energy is one of the renewable energy types, as well is among the cleanest and most economical energy sources. Nowadays, in order to provide much more energy from wind, turbine towers are being built higher and the turbine blades have begun to be manufactured longer. Due to these applications, tower and turbine weights are continuously increasing. For this reason, it is necessary to optimize the materials used as well as the dimensions of the turbine towers. In the present study, behavior of TLP floating wind turbine towers with three different designs under wave, hydrostatic and static loads were investigated. In order to clarify the effect of these loads, turbine designs were analyzed in the ratio of 1/5 using finite elements method. Steel, reinforced concrete and hybrid (reinforced concrete and steel) wind turbine towers tied to sea floor at a depth of 10 meters rigidly by TLP floating method. In this context, 10-meter-high turbine towers having three different designs which static analyzed previously were used for investigate effects of wave and hydrostatic loads. Turbine structures analyzed with ABAQUS finite elements model. The deformations and stress values of underwater turbine structures were obtained and compared with each other. As it can be seen from analysis results, compared to the reinforced concrete design, the displacement of steel tower design decreased 77.84%. It is seen that the torsion effect was dominant in the steel tower design. However, the decreasing displacement value for steel design was recorded as 44.43% compared to the hybrid tower design.
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