Ümran Esendemir

An elastic–plastic stress analysis of simply supported metal-matrix composite beams under a transverse uniformly distributed load

Abstract An analytical elastic–plastic stress analysis is carried out on metal-matrix composite beams of arbitrary orientation, supported from two ends under a transverse uniformly distributed load. The composite layer consists of stainless steel fiber and aluminum matrix. The material is assumed to be perfectly plastic during the elastic–plastic solution. The intensity of the uniform force is chosen at a small value; therefore, the normal stress component σy is neglected in the elastic–plastic solution. The expansion of the plastic region and the residual stress component of σx are determined for orientation angles of 0, 30, 45, 60 and 90°. Plastic yielding occurs for 0° and 90° orientation angles on the lower and upper surfaces of the beam at the same distances from the mid-point. However, it starts first at the lower surface for 30, 45 and 60° orientation angles. The intensity of the residual stress component of σx is found to be maximum at the lower and upper surfaces; however, the intensity of the residual stress component of τxy is a maximum on or around the x axis of the beam.

An Elasto-Plastic Stress Analysis in a Polymer Matrix Composite Beam of Arbitrary Orientation Subjected to Transverse Linearly Distributed Load:

An elasto-plastic stress analysis is carried out in a low density polyethylene thermoplastic cantilever beam of arbitrary orientation subjected to transverse linearly distributed load reinforced by Cr-Ni steel fibers analytically. In the elasto-plastic solution, the material is assumed to be perfectly plastic. The expansion of the plastic region and the residual stress component of σ x are determined for 0°, 30°, 45°, 60° and 90° orientation angles. The yielding begins at the upper and lower surfaces of the beam at the same distances from the free end. The intensity of residual stress component of σ x is maximum at the upper and lower surfaces but residual stress component of τ xy is maximum on the x axis of the beam. Sample problems are given for various angles, x axis of the beam is used to obtain the location of the elasto-plastic boundary and to calculate elastic, elasto-plastic and residual normal and shear stresses.

The Effects of Shear on the Deflection of Simply Supported Composite Beam Loaded Linearly

In this study two deflection functions due to both the flexure and the shear of an orthotropic simply supported beam loaded linearly are obtained by means of the anisotropic elasticity theory. In order to see the effect of shear, the deflections are calculated for different fiber directions. Two different composite materials are used during the deflection analysis. The error level and the shear deflection for the thermoplastic composite beam are the smallest for 45 orientation angle, and that for the polymer-matrix composite beam are the smallest for 90 orientation angle. When the cross-sectional height to the beam-length ratio increases, the shear effect also increases.

An Experimental Study of Mechanically Fastened Composite Joints with Clearance

In this article, the bearing strengths, failure modes, and joint geometries of woven glass-epoxy prepreg composite mechanically fastened joints with clearance subjected to preload moments were studied experimentally. Two different geometrical parameters were investigated. Therefore; the edge distance-to-pin diameter (E/d) and width-to-pin diameter (W/d) ratios were systematically varied and corresponding failure modes and loads were defined. The preload moments were selected as 0 and 2 Nm. The experiments were also carried out under a clearance for the diameters of the pin and the circular hole for 5 and 5.2 mm, respectively. Damage of specimens with clearance was examined using scanning electron microscope. The experimental results obtained from joints with clearance were compared with the earlier results that were not including clearance. It was observed that the effect of clearance on the bearing strength of mechanically fastened joints is significant. The failure loads of the composite joints with preload moment were larger than those of the composite joints without preload moment. Also, if geometrical parameters of mechanically fastened composite joints are varied, the failure modes and loads are strictly influenced from this variation.

Static and Dynamic Analysis of Simply Supported Beams

In this study, two deflection functions due to flexure and shear have been obtained for the global form of composite materials. Two different composite materials are selected for comparison of these deflection functions. These composites are: polymer matrix composite simply supported beam, reinforced by unidirectional fibers; and thermoplastic simply supported beam, reinforced by woven Cr-Ni steel fibers. In accordance with these different material properties, analytical and numerical solutions have been carried out. For 0, 30, 45, 60, and 90 fiber orientation angles, static and dynamic behavior of the two different composite materials are examined. Numerical solutions are given as graphical forms. In addition to modal analysis, two different composite materials have been realized. Natural frequencies and vibration modes are given as graphical forms. ANSYS and MATLAB software are used for numerical analysis of the different composite materials.

Investigating bearing strength of pin-loaded composite plates in different environmental conditions

Composites are subjected to different working environments when they are employed. In this study, the bearing strength and failure modes of composite-pinned joints subjected to various types of environments for different exposure times are investigated, experimentally. The specimens were divided into five categories which include cold environment, hot environment, humid environment, seawater environment, and room temperature. The test results were carried out after 1 and 2 months of exposure to different environmental conditions. A total of 540 test specimens with 20 different geometries were fabricated for the pin-bearing experiments. Two different geometrical parameters were investigated during analysis. The ratio of edge-distance-to-hole diameter and the ratio of the specimen width-to-hole-diameter were systematically varied and corresponding failure modes and loads were defined. The performance of the joints is closely related to changing in geometrical parameters. It was observed that different environment conditions did not change failure modes consisting of net tension, shear-out, bearing, and mixed, generally. Also, the experimental results show that the bearing strength of composite-pinned joints is affected at different levels when subjected to environmental conditions for various exposure times.

A Mathematical Model for Thermomechanical Behavior of Arbitrary Fiber Reinforced Viscoelastic Composites - II

This study examines the behavior of a composite material under mechanical loads arising of the external medium in a viscoelastic medium reinforced by two arbitrary independent and inextensible fiber families, provided that isotropy constraint is imposed on the matrix material. Despite the fact that the matrix material is isotropic the model in consideration bears the characteristic of directed media included in the transverse isotropy symmetry group solely due to its fiber distribution. The reaction of the object to external loads is expressed in elastic stress and dissipative stress. Based on constitutive axioms and concepts pertaining to the symmetry group of the material, constitutive functionals have been obtained. To materially determine arguments of these functionals, findings of the theory of invariants have been used as a routine method. As a result constitutive equations pertaining to elastic stress and dissipative stress have been found in material and spatial coordinates whereas symmetric and asymmetric stresses have been found in terms of displacement gradient and its derivative by using the expressions of elastic stress and dissipative stress. K e y W o r d s : Viscoelasticity, balance equations, isotropy, balance equations, constitutive equations.

An Elasto-Plastic Stress Analysis in a Polymer–Matrix Composite Beam Supported from Two Ends under Transverse Linearly Distributed Load by Use of Anisotropic Elasticity Theory

An analytical elasto-plastic stress analysis is carried out in a low-density polyethylenethermoplastic beam supported from two ends under transverse linearly distributed load reinforced by Cr–Ni steel fibers analytically. The material is assumed to be perfectly plastic for the elasto-plastic solution. The intensity of the uniform force is chosen at a small value; therefore, the normal stress component y is neglected in the elastic–plastic solution. The expansion of the plastic region and the residual stress component of σx and τxy are determined for 0, 30, 45, 60, and 90 orientation angles. The yielding begins at the upper and lower surfaces of the beam at the same distances from the ends. The intensity of residual stress component of x is maximum at the upper and lower surfaces but residual stress component of τxy is maximum on the x axis of the beam. The strength of the beam is increased by residual stresses.

An elastic-plastic stress analysis on a thermoplastic composite beam of arbitrary orientation supported from two ends acted upon with a force at the midpoint

An analytical elastic-plastic stress analysis is presented for a low density polyethylene thermoplastic composite reinforced by woven steel fibers supported at the ends acted upon with a force at the midpoint. The expansion of the plastic region and the residual stress component of σ x are determined for θ = 0°, 15°, 30° and 45° orientation angles. Plastic yielding occurs for 0° and 45° orientation angles on the lower and upper surfaces of the beam at the same distances from the midpoint. But, it starts first at the lower surface for 15° and 30° orientation angles. The residual stress components are obtained after releasing the external force. The residual stress component of σ x is maximum at the lower and upper surfaces. However, the intensity of the residual stress component τ xy is maxiumu on or around the x axis of the beam. The beam can be strengthened by using the residual stresses.

An Elastic-Plastic Stress Analysis in a Polymer Matrix Composite Beam of Arbitrary Orientation Supported from Two Ends Under a Transverse Uniformly Distributed Load

An analytical elastic-plastic stress analysis is carried out in a low density polyethylene thermoplastic composite beams supported from two ends under a transverse uniformly distributed load reinforced by Cr-Ni steel fibers analytically. In the elasto-plastic solution, the material is assumed to be perfectly plastic. The intensity of the uniform force is chosen as a small value; therefore, the normal stress component of σ y is neglected during the elasto-plastic solution. The expansion of the plastic region and the residual stress component of σ x are determined for 0, 30, 45, 60 and 90° orientation angles. The intensity of residual stress component of σ x is maximum at the upper and lower surfaces, but residual stress component of τ xy is maximum on the x axis of the beam. Plastic yielding occurs for 0 and 90° orientation angles on the lower and upper surfaces of the beam at the same distances from the mid point. However, it starts first at the lower surface for 30, 45 and 60° orientation angles.