Cesim Atas

Elastic–plastic stress analysis and expansion of plastic zone in clamped and simply supported aluminum metal–matrix laminated plates

Abstract An elastic–plastic stress analysis and the expansion of plastic zone in layers of stainless steel fiber-reinforced aluminum metal–matrix laminated plates are studied by using Finite Element Method and First-order shear deformation theory for small deformations. The plate is meshed into 64 elements and 289 nodes with simply supported or clamped boundary conditions. Laminated plates of constant thickness are formed by stacking four layers bonded symmetrically or antisymmetrically. It is assumed that the laminated plates are subjected to transverse uniform loads. Loading is gradually increased from yield point of the plate as 0.0001 MPa at each load step. Load steps are chosen as 100, 150 and 200.

Elastic–plastic behavior of woven-steel-fiber-reinforced thermoplastic laminated plates under in-plane loading

Abstract This paper deals with elastic–plastic stress analysis of thermoplastic laminated composite plates reinforced with woven steel fibers and containing circular holes under in-plane static loading. Residual stresses and propagation of plastic zones are obtained in simply supported symmetric and antisymmetric laminated composite plates by using a nine-node Lagrangian finite-element method. First-order shear deformation theory was used as an equivalent single-layer laminate theory for small deformations so that large plastic strains are not allowed to occur. A modified Newton–Raphson method is used as an iterative technique for determining the non-linear behavior of the material after yielding. After yielding the load is increased by means of many load steps, 0.01 MPa at each step, to follow the stress/strain curve more accurately. Mechanical properties of a layer were obtained experimentally.

An Experimental Investigation on the Impact Response of Fiberglass/Aluminum Composites

This paper presents experimental investigations on impact response of fiberglassaluminum (FGA) composites. A number of test specimens were subjected to increasing impact energies until complete perforation of the target was achieved. The damage process of fiber-glass aluminum (FGA) composites is examined by comparing the load-deflection curves, energy profile diagram (showing the correlation between impact energy and absorbed energy) and images of damaged specimens. The failure processes in the impact-loaded FGAs were initially investigated by examining the front and rear surfaces of the damaged samples. After initial examination, damage mechanisms at the interior layers were ascertained through destructive analysis, i.e., sectioning and de-plying, of samples. Careful examination of the damaged FGA panels highlighted a number of failure mechanisms such as permanent plastic deformation, tearing and shear fracture in the aluminum layers as well as fiber fracture in glass-epoxy layers, and delamination between adjacent layers, i.e., at composite/composite and composite/metal interfaces. Along with the cross-sections, images of several impacted samples for varied impact energies are provided for discussion.

The effect of face-sheet thickness on low-velocity impact response of sandwich composites with foam cores

This paper presents an experimental investigation on impact response of sandwich composite panels with different face-sheet thicknesses. A number of low velocity impact tests were performed under various impact energies. The damage process of the sandwich composites consisted of glass/epoxy face-sheets, and foam cores are analyzed from cross-examining some graphs such as load–deflection curves and damaged specimens. The primary damage modes observed are fiber fractures at upper and lower skins, delaminations between adjacent glass-epoxy layers, and core shear fractures.

Variation of the mechanical properties of E-glass/epoxy composites subjected to hygrothermal aging:

In this study, the effects of hygrothermal aging on the mechanical properties and impact behavior of glass-epoxy composites were investigated experimentally. The vacuum-assisted resin infusion molding was used to manufacture composites. In manufacturing of composites, unidirectional E-glass fabrics with areal density of 300 g/m2 and a resin system (Araldite LY 564/Aradur 3487 BD) were used. In order to determine mechanical properties such as modulus of elasticity, longitudinal and transverse strengths, shear strength, and Poisson’s ratio, the composite samples were prepared according to the ASTM standards. Then, the samples were conditioned at a constant temperature (95℃) and a constant humidity (70%) for different periods of times, ranging from 0 h to 1200 h. The conditioning temperature was chosen due to the glass transition temperature (Tg) of the intact composites which is determined as 78℃. It is noted that the most affected mechanical property via material degradation is modulus of elasticity in transverse direction (E2) while the least affected one is shear modulus (G12). The perforation threshold of the composite materials also decreases with increase of conditioning time.

An experimental and numerical investigation on low velocity impact behavior of composite plates

This paper presents an experimental and numerical investigation on low velocity impact response of S2 glass/epoxy and aramid/epoxy composite plates. Two different impact energy levels, 20 J and 30 J, were considered for impact tests. The commercial software called LS-DYNA was used in order to perform numerical simulations. The experimental and numerical results were found to be in good agreement.

Material nonlinear behavior of laminated metal–matrix composite plates supported at edges under uniform traverse loading

Abstract This paper deals with material non-linear behavior of steel fiber reinforced aluminum metal–matrix composite plates prepared by the squeeze casting process. By such an analysis it is intended to form an opinion about elastic–plastic behavior of laminated plates used in engineering problems associated with structural designs. Therefore, loads that begin plastic flow at any point of laminate for various stacking sequences are obtained. Afterwards, how further increase in loads gradually causes spreading of plastic zone is examined. Elastic/plastic and residual stress variations correspond to diverse stacking sequences of laminated plates are illustrated in figures. Plastic zone expansions are displayed in simply supported symmetric and antisymmetric laminated composite plates by contour plots. The finite element method is applied for analyses based on small deformation effects including shear deformation. For nonlinear solution of the problem a combined incremental/iterative procedure (modified Newton–Raphson) is followed and load increments are chosen to be sufficiently small to obtain a rapid-converged equilibrium state. Mechanical properties of an orthotropic layer are obtained experimentally.

The Effects of Composite Plate Design Parameters on Linear Vibrations by Discrete Singular Convolution Method

This study is devoted to some specific free vibration analysis of thin composite plates based on discrete singular convolution (DSC) approach. As the first analysis, a parametric study is performed on the basis of number of lamination, boundary condition, and orientation angle of symmetrically laminated composite plates. As the second, the effects of material type, boundary condition, and stacking sequence on the modal characteristics of laminated plates made of E-glass/epoxy, Kevlar/epoxy, and carbon/epoxy are investigated. Thirdly, linear modal characteristics of fiber metal laminates are specifically analyzed due to their common use in aircraft design. Hopefully, the results presented in the article may be practically of interest for engineers and designers. This study displays the applicability of the DSC method for real-life problems.

Nonlinear Stress Analysis of Unidirectionally Reinforced Symmetric Aluminum Metal-Matrix Laminated Beams under a Bending Moment

This study deals with elastic-plastic behavior of aluminum metal-matrix laminated cantilever beam subjected to a bending moment at the f ree end. The Bernoull i-Euler theory is utilized in the solution and small plastic de format ions are considered. The beam consists of four layers and its material is assumed to be linearly hardening. A few ply arrangements such as [9070° ] s , [ 3 0 7 3 0 ° ] s , [ 4 5 7 4 5 ° ] s and [607 -60° ] s are taken into considerat ion for such an analysis. The moment values that initiate plastic f low at any point of the beam are carried out for diverse stacking sequences. The variation of the elastic, elastic-plastic and residual stress components versus increasing plastic zone spread are given in tables and figures.

Damage behavior of potting materials in sandwich composites with pinned joints

Abstract The damage behavior of the potting materials around a pinhole, being used in the mechanical joints of sandwich composites, is investigated experimentally. The sandwich composite panels used in the tests were manufactured by the vacuum-assisted resin infusion technique. Each of the top and bottom face sheets of the panels consisted of two woven E-glass/epoxy layers. As the core material, PVC foam (AIREX® C70.55) was used. The potting material consists of an epoxy resin and hardener system mixed with short E-glass fibers (4 wt%). The diameter of the potting material D and the edge distance to the center of pinhole E were considered as the two main varied dimensions. They were chosen as D=10, 12, 15, and 18 mm and E=15, 20, and 25 mm. The damage mechanisms of the potting material and sandwich sections are presented by using load-displacement variations and images of the damaged samples, subjected to in-plane pin loading.