Numan Behlül Bektaş

Elasto-plastic stress analysis in simply supported thermoplastic laminated plates under thermal loads

Abstract In this study, an elasto-plastic stress analysis is carried out on symmetric cross-ply [0°/90°]2 and symmetric angle-ply [30°/−30°]2, [45°/−45°]2, [60°/−60°]2 thermoplastic laminated plates. Laminated composite plates are simply supported and subjected to constant temperature change through the thickness. An analytical solution is performed for satisfying thermoelasto-plastic stress/strain relationships and boundary conditions for small plastic deformations. The composite materials are assumed to be perfectly plastic. The Tsai-Hill theory is used as a yield criterion. Residual stress components, σ x r and σ y r , for cross-ply laminated plates have some magnitudes but τ xy r are zero. The magnitudes of residual stress components increase gradually depending on the temperature increment. For symmetric angle-ply laminated plates, residual stresses are found zero except τ xy r .

Stress analysis of functionally graded discs under mechanical and thermal loads: analytical and numerical solutions

Abstract This study deals with stress analysis of functionally graded discs subjected to internal pressure and various temperature distributions, such as uniform T, linearly increasing To, and decreasing Ti temperatures in radial directions. For analytical study, the closed-form solutions for stresses and displacements are obtained by using the infinitesimal deformation theory of elasticity. For graded parameters, power law functions are used in analytical and numerical solutions. For numerical study, discs are modeled and analyzed by using a commercial finite element program, ANSYS®. Metal matrix composite, AlSiC, is selected as disc material. Results obtained both analytical and numerical solutions are found very well consistent with each other. The tangential stresses are found higher than the radial stresses at the inner surface for all thermal loads, and they vary from compressive to tensile and from tensile to compressive depending on the functionally graded material (FGM) properties and temperature loads. The radial stresses are found zero at the inner and outer surface and higher at one third of the disc section near the inner surface. They are also found as compressive and tensile stresses depending on the material properties and temperature loads.

Elastic-Plastic and Residual Stress Analysis of a Thermoplastic Composite Hollow Disc under Internal Pressures

This article deals with the elastic-plastic stress analysis of a thin thermoplastic composite disc under internal pressures. An analytical solution is performed for satisfying elastic-plastic stress-strain relations and boundary conditions for small plastic deformations. Because of the material properties, the composite disc is assumed to be elastic-perfectly plastic, and the Tsai-Hill Criterion is used as a yield criterion. Elastic-plastic and residual stress distributions are obtained from the inner radius to the outer radius, and they are presented in tables and figures. All radial stresses r are compressive, and they are highest at the point where the plastic deformation begins. All tangential stresses are tensile, and they are highest at the inner radius. The magnitude of tangential residual stresses is higher than that of the radial residual stresses, and it changes nonlinearly from the inner radius to the outer radius.

Elastic-Plastic Stress Analysis on Simply Supported Thermoplastic Laminated Plates Under Thermal Loads Varying Linearly

In this study, elastic-plastic stress analysis is carried out on simply supported symmetric cross-ply [0 / 90]2 and angle-ply [30 / 30]2, [45 / 45]2, [60 / 60]2 thermoplastic laminated plates under thermal loads varying linearly through the thickness. An analytical solution is performed for satisfying thermal elastic-plastic stress-strain relations and boundary conditions for small plastic deformations. Tsai-Hill Criterion is used as a yield criterion. The composite material is assumed to be linear hardening. Residual stresses distributions along the thickness of the plates are obtained and presented in figures. All the residual stress moments are in balance with respect to middle plane of the laminates since they are symmetric in opposite signs.

Thermo-Elastic Stress Analysis in a Thermoplastic Composite Disc

This study deals with thermo-elastic stress analysis on a thermoplastic composite disc reinforced curvilinearly with Ε-glass fibers. Its mechanical properties are obtained by using an Instron testing machine. The modulus of elasticity in the tangential direction is measured by using strain gauges due to the fitting of a solid disc into the composite disc. An analytical method is performed to determine thermal stresses for both uniform and linearly changing temperatures. The magnitude of the tangential stress component in polar coordinates is the highest at the inner surface of the disc. INTRODUCTION The stress analysis of discs has long been an important issue in engineering design. Due to high specific stiffness and strength, improved fracture toughness and increased impact resistance, thermoplastic composites have gained popularity. Ito et al. I\l have presented an attempt at tailoring thermoplastic laminates with near-zero coefficients of thermal expansion in one particular in-plane direction by using conventional low-cost glass fibers. Sayman and Qallioglu 121 have investigated elastic-plastic stress analysis in steel fiber reinforced thermoplastic composite cantilever beam analytically. Timoshenko and Goodier /3/ have presented a thermal stress analysis in an isotropic thin disc. Genta and Gola /4/ have investigated an analytical linear stress analysis in orthotropic rotating discs reinforced by fibers rectilinearly. Giiven and Altay 151 have studied thermal stresses in a linear hardening solid disc under a uniform heat source. Tütüncü 161 has determined stresses and deformations resulting from centrifugal forces in rotating specially orthotropic circular plates are determined. Trende et al. Ill have investigated residual stresses and dimensional changes in the compression moulded glass-mat reinforced thermoplastic (GMT) parts. A heat transfer and crystallization model with temperature dependent matrix properties has been used to obtain input to the subsequent thermal stress analysis. Shabana and Nöda /8/ have examined the thermoelastoplastic stresses in functionally graded composite materials by the finite element technique. Mackin et al. 191 have studied thermal cracking in disc brakes during hard braking. In this study, a low-density thermoplastic composite disc reinforced with Ε-glass fibers is manufactured, and its mechanical properties are determined. An analytical method is carried out on the composite disc to obtain thermo-elastic stresses under uniform and linear temperature distribution. PRODUCTION OF THE COMPOSITE DISC The composite material consists of a thermoplastic matrix with a low-density polyethylene and E-glass fibers. For preparing a polyethylene layer, 20 grams polyethylene granules were placed into the mould and heated up to 160°C by an electrical resistance. The material was kept for a five minute period at 160°C under 2.5 MPa pressure by means of a hydraulic press. Subsequently, the temperature was decreased to 30°C in five minutes under 15 MPa pressure. At the result of this process, a polyethylene layer with a thickness of 1 mm was produced. After the wound Ε-glass fibers were placed between two polyethylene layers, these materials were heated up 251 Vol. 12, No. 4, 2005 Thermo-Elastic Stress Analysis in a Composite Disc to 160°C under 2.5 MP a pressure for ten minutes. As a result of this process, an Ε-glass fiber-reinforced composite disc was produced as shown in Figure 1. The thickness of the composite disc and the outer radius are 2.5 mm and 75 mm, respectively. DETERMINATION OF MATERIAL PROPERTIES For the composite material, the volume fraction of fibers is Vf =10%. Test specimens were used to determine the material properties of the composite disc. The modulus of elasticity in the transverse direction of Ε-glass fibers was defined as Er and it was given in the direction of Ε-glass fibers as Eg . Poissons ratio (vre) and Er were measured by strain gauges bonded onto the test specimen as shown in Fig. 2a. The strains were measured as εΓ = \25μ and εβ = \.5μ . Therefore, Er and Poissons ratio (v r g ) were found as 190 MP a and 0.012, respectively. Determination of Εθ In order to find E

ELASTIC–PLASTIC STRESS ANALYSIS OF LAMINATED COMPOSITE BEAMS UNDER LINEAR TEMPERATURE DISTRIBUTION

a circular aluminum solid disc was fitted into the thermoplastic composite disc as shown in Figure 3. Because of this fitting, a pressure ρ appeared, which caused the aluminum solid disc to shrink. Strains measured in the radial and tangential directions in the aluminum solid disc were -8 μ. The external pressure in the solid disc was found as p=-0.8 MPa. Furthermore, the strains on the composite ring were obtained in the radial and tangential directions, respectively as εΓ=-\52μ and £ # = 1 4 5 / / . Hooks laws for the stresses in the radial and tangential directions are given as

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

This study deals with elastic–plastic stress analysis of symmetric laminated composite beams with perfectly clamped ends under linear temperature distribution. The Bernoulli–Euler theory is used during the solution considering infinitesimal small deformations. The composite beam is assumed to be linear strain hardening. The Tsai–Hill theory is used as a yield criterion in the solution. The stacking sequences of the composite beam are chosen as (90°/0°)s, (30°/−30°)s, (45°/−45°)s, (60°/−60°)s and also (0°)4 and (90°)4 in comparison with the composite beam of a single layer in the literature. The results obtained are in good agreement with the literature. The temperature that causes plastic yielding is found to be highest for the (30°/−30°)s stacking sequence, in order to compare with the others, except for the (0°)4 orientation. Residual thermal stresses are particularly important because they can increase the strength of the composite or may lead to premature failure. The residual stress components (σ x ) r are found to be highest at the upper and lower surfaces. When the plastic region expands further with increased temperature, the residual stress components become highest at the elastic–plastic interface.

THERMAL ELASTIC-PLASTIC STRESS ANALYSIS OF STEEL WOVEN REINFORCED ALUMINUM METAL–MATRIX COMPOSITE LAMINATED PLATES

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.

Thermal Elastic-Plastic Stress Analysis of Symmetric Aluminum Metal-Matrix Composite Laminated Plates and Residual Stresses Under Thermal Loads Varying Linearly

In this study, an elastic-plastic stress analysis is carried out on symmetric cross-ply [0°/90°]2 and angle-ply [30°/−30°]2, [45°/−45°]2, [60°/−60°]2 steel woven reinforced aluminum metal–matrix laminated plates under thermal loads varying linearly along the thickness. Laminated composite plates are simply supported and subjected to linear temperature change through the thickness as T 0 at the upper and lower surfaces and T at the middle plane, respectively. An analytical solution is performed for satisfying thermal elastic-plastic stress–strain relations and boundary conditions for small plastic deformations. The composite materials are assumed to be linearly hardening. The Tsai–Hill criterion is used as a yield criterion. Plastic and residual stress distributions along the thickness of the plates are obtained. Plastic and residual stress components, σ x ) p , (σ y ) p and (σ x ) r , (σy) r , have some magnitude but (τ xy ) p and (τ xy ) r are zero for all stacking sequences. All the residual stress components are in static balance with respect to the middle plane of the laminates since they are symmetric in opposite signs. The magnitude of the residual stress components is the highest at the upper and lower surfaces.

Thermal Elastic-Plastic Stress Analysis in Simply Supported Thermoplastic Laminated Plates

This paper deals with elastic-plastic stress analysis of symmetric cross-ply [0/90]2 and angle-ply [30/30]2, [45/45]2, [60/60]2 aluminum metal-matrix laminated plates under thermal loads varying linearly along the thickness. The temperature is T0 at the upper and lower surfaces, respectively. The solution is performed for satisfying thermal elastic-plastic stress-strain relations and boundary conditions for small plastic deformations. Tsai-Hill Criterion is used as a yield criterion. Residual stresses distributions along the thickness of the plates are obtained. All the residual stress components are in static balance with respect to middle plane of the laminates since they are symmetric in opposite signs. The magnitude of the residual stress components is the highest at the upper and lower surfaces.