Gürkan Altan

Stress Analysis of Curvilinearly Orthotropic Rotating Discs under Mechanical and Thermal Loading

This study deals with the thermal stress analysis of a curvilinearly orthotropic rotating annular disc under internal and external pressures. The temperature distribution is chosen to vary parabolically from the inner surface to the outer surface along the radial section. With an increasing temperature, the tangential stress component decreases at the inner surface whereas it increases at the outer surface, and the radial stress component goes down gradually. The magnitude of the tangential stress component is higher than that of the radial stress component. The radial displacement is calculated analytically and has higher values at the inner surface than that of the outer surface, for all the temperature distributions. The stresses and the radial displacement obtained are also compared with the stresses and displacement in a rectilinearly hollow rotating disc of [Çallioğlu, H., Stress Analysis of an Orthotropic Rotating Disc under Thermal Loading, J. Reinforced Plastics and Composites, (in press)].

Flexural behavior of 3D printed honeycomb sandwich structures with waste filler material

Abstract In this study, the flexural behavior of filled and unfilled honeycomb structures was experimentally examined. As filler material, waste materials of the furniture and marble industry were used. In this context, effects of the wastes of the furniture industry (i. e., pine sawdust) and of the marble industry (i. e., travertine powder) on the flexural behaviors of honeycomb structures were investigated by the three point flexural test. Honeycomb specimens were produced by using PLA plastic material in a 3D printer by rapid prototyping techniques. By changing cell sizes of the honeycomb structures used in the flexural tests, the relation between the waste filler materials and the cell size was also investigated. The flexural behavior of unfilled honeycomb specimens was at maximum for the specimens with small cell size. In the honeycomb structures filled with waste material, it was determined that the flexural loads of small cell sized specimens were decreased by approx. 10 % while the flexural loads of big cell sized specimens were increased by approx. 10 %. As a result, it was found that the flexural behavior of unfilled honeycomb structures with big cells which have low flexural behavior could be increased using waste filler material.

Thermo-elastic stress of a metal-matrix composite disc under linearly-increasing temperature loading by analytical and FEM analysis

In this study, the elastic stress analysis of a composite disc with aluminium matrix subjected to a linearly-increasing temperature distribution has been carried out. The values of tangential and radial stress components that have occurred under the effect of the temperature from the inner surface of the disc towards the outer surface have been obtained by two different methods, numerical and analytical. In the analytical analysis, a computer program has been developed to get the values of thermal stresses. But in the numerical study carried out with the finite-element method, Abaqus 6.8 package program has been used. As a result of these analyses, it has been observed that the stress values obtained from both methods support each other. It has been determined under this temperature distribution that tangential stress components are always on the condition of compression in the inner surface of the disc and of tensile in the outer surface. It has also been found out that radial stress components are always in the state of tensile along the whole profile of the disc. Finally, the stress analysis of the same composite disc subjected to this temperature distribution, but with a reduced mass, has also been examined numerically.

Elastic-Plastic and Residual Stress Analysis of an Aluminum Metal-Matrix Composite Disk under Internal Pressures:

This paper deals with the elastic-plastic stress analysis of a thin aluminum metal-matrix composite disk under internal pressure. An analytical solution is performed for satisfying the elastic-plastic stress-strain relations and boundary conditions for small plastic deformations. The Tsai-Hill Criterion is used as a yield criterion, and an elastic-perfectly-plastic material is assumed. Elastic-plastic and residual stress distributions are obtained from inner radius to outer radius, and they are presented in the tables and figures. All radial stresses, σr, are compressive, and they are highest where the plastic deformation begins. All tangential stresses, σ θ , are tensile, and they are highest at the inner radius. Magnitude of the tangential residual stresses is higher than that of the radial residual stresses, and it is changing from negative sign to positive.

An investigation on damage loads of mechanical butt joints in composite structures

With the advanced technology of our time comes an increased need for high quality materials. The conventional engineering materials are no longer adequate to suit the needs of the manufacturing process. Therefore, there is constant growth in the fields of the use of composite materials formed by the combination of two or more materials. Also various difficulties occur in the field where the composite materials are used. The systems which will be used both in the manufacturing process and in engineering designs are composed of more than one component. Therefore, the components should be jointed for the system designed. These joints are enabled with mechanical and bonding techniques. In this study, mechanical joints made with a joint lock having I profile have been recommended for use instead of the bonding technique in the butt joint of the composite plates. Load-carrying capacities of the locks of different dimensions formed with the exchange of basic geometric parameters that characterize I profile joint lock and its effects on the first damage have been analyzed experimentally and numerically. Determining the optimal joint with the best strength has also been conducted. The composite structure has been prevented from complete damage by the determination of the initial damage that may occur on I profile joint lock. Thus, the lifespan of the composite structure has been increased with the exchange of the lock component.

Assessment of the buckling strengths of composite plates impacted with different impact loads and points

This study has been designed to experimentally assess the changes of buckling loads of the E-glass fiber/epoxy composite laminates impacted at different impact energy levels. With the experiments conducted, the effects of the geometry parameters such as the ratio of impact point to the length of buckling (G = y/L) have been examined. According to the results of the experiments made, when the ratio of impact position is 0.2, buckling behaviors of the impacted specimens made at the energy levels of and under 10 J have been determined to be almost the same as the buckling behaviors of the non-impacted specimens. Generally, it has been found out that buckling behaviors of the impacted specimens made at the energies under such levels of energy as 15 J increase with the impact point ratio, and when the ratio is 0.2, buckling behaviors have been observed to be maximum.

Elastic-Plastic Stress Analysis of Thermoplastic Composite Beams Loaded by a Single Force

In this study an elastic-plastic stress analysis is carried out in a woven thermoplastic fiber-reinforced thermoplastic composite cantilever beam loaded by a constant single force at its free end. The expansion of the plastic region and the residual stress component of x are determined for 0, 15, 30, and 45 orientation angles. Yielding begins for 0 and 45 orientation angles of both upper and lower surfaces of the beam at the same distances from the free end. An elastic-plastic analysis is carried out for the plastic region, which spreads both at the upper and lower surfaces. The residual stress components are obtained after releasing the external force. The distributions of the residual stress components of x are also determined. The intensity of the residual stress components of x is maximum at the upper or lower surfaces of the beam.