Cutout Orientation Research Articles

Strength Prediction and Damage Assessment of Laminated Composite Plates With Rectangular/Square Cutout Using Finite Element Method

The progressive failure analysis of symmetrically laminated rectangular composite plate [0/+45/-45/90]2s with square/rectangular cutout under uniform uniaxial compression loading is carried out using finite element method. Hashins failure criterion is used to predict the failure of lamina. A parametric study has been carried out to study the influence of square/rectangular cutout size, cutout orientation and plate thickness on the ultimate failure load of laminated composite plate under uni-axial compression loading. Ultimate failure loads were computed for six different laminate configurations [0/+45/-45/90]2s, [75/-60/30/-15]2s, [0/90]4s, [-45/45]4s, [15/-75]4s, [30/-60]4s. It is observed that the laminate stacking sequence, plate thickness , cutout size and cutout orientation has substantial influence on the ultimate failure load of notched composite plates.

Dynamic instability analysis of perforated stiffened laminated composite panels subjected to non-uniform in-plane edge load under hygrothermal condition

A robust and computationally efficient finite element (FE) formulation has been developed in an effort to understand the parametric instability behaviour of a perforated stiffened composite panel subjected to a pulsating non-uniform edge load under a hygrothermal environment. The panel is modelled using a 9-noded heterosis element to avoid shear locking, whereas the stringer uses a 3-noded isoparametric beam element with a displacement compatibility condition employed at the skin–stringer​ interface. Due to the non-uniform distribution of stress in the perforated panel as a result of exposure to environmental and mechanical loading conditions, a unique dynamic technique has been implemented to account for the instability performance by employing two types of boundary conditions. In the current investigation, an unstiffened panel is initially obtained based on the highest value of the dynamic instability opening (DIO) and the unstable excitation frequency of the panel for different lamina schemes, cutout shapes, and loading conditions. The obtained unstiffened panel is further investigated for various stiffener configurations to determine a highly unstable perforated stiffened panel based on the DIO value and instability zone frequency range. Detailed parametric studies are then carried out considering the cutout sizes, cutout orientation, panel’s aspect ratio, and stiffener depth to understand the parametric instability behaviour of the panel in a hygrothermal environment. It is found that moisture significantly influences the dynamic instability behaviour of the perforated stiffened panel compared to the temperature exposure by shifting the instability zone towards the lower frequency. The width of the instability region of the stiffened panel broadens abruptly as the magnitude of the applied static in-plane edge load enhances. Also, for certain combinations of the dynamic and static load factors, the lower bound of the instability region reduces to zero, resulting in fluttering. In general, it is observed that stiffer the panel, wider is the instability zone with a higher unstable excitation frequency range.

Effect of elliptical cutouts on buckling and vibration characteristics of stiffened composite panels under non-uniform edge loads

This study is motivated by the need to understand the effect of elliptical cutouts on the buckling and vibration characteristics of stiffened composite panels under the influence of various types of non-uniform in-plane edge loads. The study is carried out by using a Finite Element (FE) formulation wherein the plate, and the stiffener are discretized by employing a 9-noded heterosis plate element and a 3-noded isoparametric beam element, respectively. The contributions of shear deformation and rotary inertia are considered in the FE formulation. Since the stress distribution within the panel is highly non-uniform for a given loading and geometric imperfection, a dynamic approach has been adopted to solve the buckling problem wherein two sets of boundary conditions are used to calculate the pre-buckling stresses and the buckling load of the stiffened panel. A new structured mesh pattern is proposed to house the stiffeners attached to the centrally located elliptical cutout panel in the form of a grid so that the stiffener can be attached anywhere and in any direction as per the requirements. The influences of various parameters, such as ply orientation, cutout size, cutout orientation, boundary conditions and depth to width ratio of the stiffener, are examined in detail. From the analysis, it is noticed that the depth of the stiffener has a significant effect on the buckling and vibration characteristics of the panel.

Effect of cutout geometry on the failure strength of symmetric laminates under uniform heat flux

The present work aims to investigate the thermal stress distribution in an infinite symmetrical laminated composite plate with a polygonal cutout to determine the laminate failure strength based on the first ply failure according to Hashin–Rotem and Tsai–Wu criteria. Lekhnitskii’s solution technique has been used to obtain the required potential functions. The extension of the technique used for the circular and elliptical cutouts into polygonal cutouts was performed using conformal mapping function in accordance with the procedure of complex variables. The main parameters such as cutout orientation, bluntness factor, the aspect ratio of the cutout, as well as stacking sequences in composite plates with symmetrical laminates made of glass/epoxy material containing triangular, square, pentagonal, and hexagonal cutouts have been examined. According to the research findings, it is possible to improve the failure strength of perforated plates by appropriate selection of cutout shapes along with the optimum values of the effective parameters. The unexpected result was that circular geometry was not always the best choice for the cutout because the selection of appropriate values for the parameters under consideration for a laminate with non-circular cutout leads to higher failure strength compared to the same plate with circular cutout.

Determination of the Effective Parameters for Perforated Functionally Graded Plates with Polygonal Cutout by Analytical Solution

This paper investigates the moments and stress resultants from infinite FG laminates with different polygonal cutouts subject to uniaxial tensile load. The analytical solution used for the calculation of stress resultants and moments is the basis of the complex-variable method and conformal mapping function. The impact of various factors, namely cutout orientation angle, cutout aspect ratio as well as the cutout corner curve on stress distribution and moment resultants is studied. The effect of the aforementioned parameters around triangular, square, pentagonal and hexagonal cutout is analyzed. The mechanical characteristics of the graded plates are hypothesized to vary throughout the thickness exponentially. Finite element numerical solution is employed to examine the results of the present analytical solution. This comparison showed a favorable agreement level among the acquired analytical and numerical outcomes.

Buckling analysis of thin cylindrical CFRP panel with oval cutout

Abstract The use of laminated composite is growing rapidly in many fields due to their high stiffness to weight and strength to weight ratios, low modulus of expansion, thermal conductivity etc. According to their applications, composite materials undergo different loading conditions. One of the common failures is buckling, when the laminate is subjected to axial compressive load. Hence buckling analysis of composite structure is very important from design point of view. Different cutout shapes of thin cylindrical shells have been studied for buckling, but oval shaped cutouts with different orientations seems scanty and requires more investigation. In the present study, buckling analysis of thin cylindrical carbon fiber reinforced polymer (CFRP) composite shell with oval cutout has been investigated. The effects of three types of variables viz. layup orientation, element type and cutout orientation are analyzed numerically. The results show that the buckling load and mode shape depend on all three variables. The four ply stack orientations panel show significantly higher buckling load than two ply stack, and large decrease in buckling load with respect to cutout orientation. The buckling modes are highly affected by the cutout orientation. The minimum value of buckling load with respect to cutout orientation depends upon layup configuration. The lowest value of buckling load has been obtained for configuration 2 at 90° cutout orientation.

Nonlinear Buckling Analysis of Steel Cylindrical Shell with Elliptical Cut-out Subjected to Longitudinal Compressive Load

The current paper investigates the effect of cut-out design parameters on load-bearing capacity and buckling behaviour of steel cylindrical shell using a nonlinear finite element analysis in modelling cylinder buckling under longitudinal compressive load. The effect of four geometry design parameters: shell diameter to thickness ratio, cut-out location, orientation, and size were investigated in this study. To enhance the prediction of buckling behaviour, both geometrical and material nonlinearities were considered. An ANSYS APDL code was written and tested by verifying its validity through comparison with former buckling study. The results showed that changing the cut-out location from mid-height of the cylindrical shell towards a fixed edge caused an increase in the buckling load value. Moreover, the study showed that increasing parameters such as shell thickness and cut-out orientation have a positive influence in which the buckling load value increased too. For fast design purposes, an empirical numerical based regression formula was presented for the calculation of the critical buckling load of a cylindrical shell having an elliptical cut-out.

Determination of optimum effective parameters on thermal buckling of hybrid composite plates with quasi-square cut-out using a genetic algorithm

ABSTRACTThe thermal buckling load on perforated composite plates is affected by several parameters, including design variables such as cut-out orientation, fibre angle, bluntness of cut-out corners, cut-out size to plate size ratio and stacking sequence. This study investigates the effect of these parameters on the thermal buckling load of a composite plate with a quasi-square cut-out. Optimal values of the parameters are determined using a genetic algorithm to achieve the maximum buckling load. The composite used herein is a four-layer laminated composite plate. The stacking sequences of the plate are also studied. Stability equations are obtained using first order shear deformation theory. The results showed that a plate with a quasi-square cut-out is more resistant to thermal buckling than one with a circular cut-out; thermal buckling of a composite plate is dependent on various parameters, and the maximum thermal buckling load can be achieved by appropriate selection of these parameters.

Effects of Cut-Out Orientation and Fiber Angle on Stress Concentration in an Infinite Orthotropic Plate

The presence of cutout in structures may result in strength degradation due to alteration of load lines around the cutout. The effects of these cutouts on stress field should be studied carefully while designing of any material. This article presents the optimum design of an infinite orthotropic plate weakened by complex cutout using a genetic algorithm where cutout orientations and fiber angles are considered as design variables. The stress concentration factor is used as fitness function derived using the Muskhelishvili’s complex variable approach for various in-plane loadings. The effects of cutout orientation and fiber angles on stress concentration are discussed.

General solution of stress field in exponential functionally graded material plates containing a quasi-rectangular cutout

In this paper, using an analytic technique based on complex variable method, the stress resultants and moments in infinite functionally graded plates with rectangular cutout under uniaxial tensile load are investigated. The mechanical properties of the functionally graded plate are assumed to change exponentially. The effect of different parameters such as cutout orientation, aspect ratio of the cutout, and cutout corner curvature on the distribution of stress resultants and moments is investigated. To verify the accuracy of the presented analytical method, its results are compared with the numerical results obtained from finite element modeling in ABAQUS. The comparisons demonstrate a good level of agreement between the obtained numerical and analytical results. According to the results, the above parameters have a significant impact on the distribution of stress resultants and moments around the cutout, and the load-bearing capacity of the functionally graded plates with cutouts can be improved by careful selection of these parameters.

Numerical Analysis of Stress Concentration in Isotropic and Laminated Plates with Inclined Elliptical Holes

The design of high-performance composite structures frequently includes discontinuities to reduce the weight and fastener holes for joining. Understanding the behavior of perforated laminates is necessary for structural design. In the current work, stress concentrations taking place in laminated and isotropic plates subjected to tensile load are investigated. The stress concentrations are obtained using a recent quadrilateral finite element of four nodes with 32 DOFs. The present finite element (PE) is a combination of two finite elements. The first finite element is a linear isoparametric membrane element and the second is a high precision Hermitian element. One of the essential objectives of the current investigation is to confirm the capability and efficiency of the PE for stress determination in perforated laminates. Different geometric parameters, such as the cutout form, sizes and cutout orientations, which have a considerable effect on the stress values, are studied. Using the present finite element formulation, the obtained results are found to be in good agreement with the analytical findings, which validates the capability and the efficiency of the proposed formulation. Finally, to understand the material parameters effect such as the orientation of fibers and degree of orthotropy ratio on the stress values, many figures are presented using different ellipse major to minor axis ratio. The stress concentration values are considerably affected by increasing the orientation angle of the fibers and degree of orthotropy.

Optimum Design of Perforated Orthotropic and Laminated Composite Plates under in-plane loading by genetic algorithm

In this paper, the parameters influencing the stress distribution around regular polygon cutouts in orthotropic plates and symmetrical composite laminates are studied, and then the genetic algorithm is used to determine the optimal values of effective parameter for attaining the lowest normalized stress and the highest failure strength. The parameters examined for this purpose are cutout geometry, curvature radius of cutout corners, cutout orientation, fiber angle, and load angle and stacking sequence of laminated composite. An analytical method is used to calculate the stress distribution around different cutouts under different in-plane loads. Using conformal mapping and complex variable method, the Lekhnitskii’s method that is originally introduced for circular and elliptical cutouts is expanded for cutouts with different shapes. The results show that the failure strength of perforated plates can be improved by choosing the appropriate shape of cutout and the optimal values of the effective parameters. The results show that contrary to expectation, the best cutout geometry is not always a circle, as in some cases by choosing the appropriate values of bluntness parameter, cutout orientation, and stacking sequence for a laminate with non-circular cutout the failure strength higher than that of a circular cutout can be achieved.

On the stress concentration around a polygonal cut-out of complex geometry in an infinite orthotropic plate

The best values of fiber volume fractions, fiber arrangements, and cut-out orientations in an orthotropic infinite plate weakened by a polygonal discontinuity of regular and complex geometry are investigated in the present work. Considering the stress concentration factor as a fitness minimization function, the genetic algorithm is employed and, elastic constants and stresses are computed utilizing the Mori-Tanaka theory and the Muskhelishvili’s complex variable method, respectively. The upshot of present work shows a substantial impact of fiber volume fraction, fiber arrangement and, corner radius and orientation of cut-out, on values of stress concentration factor for various in-plane loading conditions. Furthermore, the database of the complex constants used in the Schwarz–Christoffel mapping to develop distinct complex shapes is also reported.

Studying the effect of different parameters on stress resultant and moments distribution around non‐circular cutouts in unsymmetric laminates

AbstractIn this study, using complex potential approach, the stress analysis of unsymmetric laminates with non‐circular cutouts is examined. In this study, using an appropriate mapping function the solution of perforated unsymmetric laminate with a circular cutout is extended to calculate stress distribution around non‐circular cutouts and the effect of some parameters such as lay‐up, cutout orientation and bluntness of cutouts on the stress resultants and moment resultants around them is studied. The results obtained are presented for two different lay‐ups [0/90]T and [45/–45]T. Finite element numerical solution is used to validate results obtained from the present analytical solution. The analytical solution is in conformity with the finite element solution. It is interesting to note that the unexpected results indicate that the stress resultants and moment resultants around circular cutout aren't less than other cutouts. Furthermore, if appropriate values are selected for bluntness and cutout orientation, the stress resultants and moments will be reduced in significant value.

SCF in Isotopic & Orthotropic Plates Part II: Biaxial Load

This is the second of two companion papers which collectively present a comprehensive 3D finite element analysis on stress concentration in isotropic and orthotropic plates. Any design engineer must know the effect of the various parameters on the stress distribution and strength to successfully design a machine element. The following research makes an attempt to study the effect of cutout orientation and bluntness ratio on the Stress Concentration Factor (SCF) of biaxial loaded isotropic and orthotropic plates. ANSYS APDL environment has been used here to carry out the 3D analysis. The bluntness ratio r/R=0.2 is most effective in terms of percentage reduction in SCF as compared to higher bluntness ratios. The percentage reduction in SCF with r/R=0.2 is about 35% for Mat 1 and Mat 3 and about 50% for Mat 2.

Progressive Failure Analysis of Laminated Composite Plates with Elliptical or Circular Cutout Using Finite Element Method

The progressive failure analysis of symmetrically laminated composite plate [0°/+45°/-45°/90°]2s with circular or elliptical cutout under uniform uniaxial compression loading is carried out using finite element method. Hashin's failure criterion is used to predict the lamina failure. A parametric study has been carried out to study the effect of elliptical / circular cutout orientation, cutout size and plate thickness on the ultimate failure load of laminated composite plate under uni-axial compression loading. It is noticed that elliptical cutout orientation has influence on the strength of the notched composite plates. It is observed that the laminate size of the elliptical/circular cutout and plate thickness has substantial influence on the ultimate failure load of notched composite plates.

Optimum design of laminated composite plates containing a quasi-square cutout

In this paper, an attempt has been made to calculate the optimal values of effective parameters on the stress distribution around a quasi-square cutout using different optimization algorithms such as Particle Swarm Optimization (PSO), Genetic Algorithm (GA) and Ant Colony Optimization (ACO). To achieve this goal, the analytical results of symmetric laminated composite plates containing a square cutout have been used. The analytical solution can be achieved with the development of the Lekhnitskii solution method. This method is based on using complex variable method in the analysis of two-dimensional problems. In order to use the method in stress analysis of laminates containing a square cutout, by using conformal mapping, the area outside the square cutout is mapped to the area outside of a unit circle. Effective parameters on stress distribution around the square cutout in symmetric laminated plates considered as design variables include: load angle, cutout orientation, bluntness and the stacking sequence of the laminate. Cost function in this problem is the maximum stress created around the cutout calculated by the analytical solution method. Another goal of this paper is to investigate the performance of aforementioned optimization algorithms. The results show that the PSO algorithm converges earlier than the other two methods and have the better cost function.

Mechanical Characterization and Finite Element Investigation on Properties of PLA-Jute Composite

materials are on high demand in recent days amongst high performance products that need to be strong enough in severe loading conditions. It can be developed with a suitable combination of matrix and reinforcement materials to meet the requirement of specific applications. The present work attempts to form composite plates using a combination of natural polymers and fibers to improve certain properties. The focus is to develop a biodegradable composite of comparable properties with those available commercially. The formed plates are tested to determine different mechanical properties such as tensile strength, impact resistance, hardness etc. The thermal parameters are also determined by DSC (Differential scanning calorimetry) test. A finite element analysis is conducted and the results have been compared with Graphite epoxy composite for checking the effective use of this material. responses along with vibration behavior of laminated composite plates have been extensively investigated. Pandya and Kant (6) has proposed a C0 continuous displacement finite element formulation of laminated composite plates under transverse loading using Higher order Shear Deformation theory. The static behavior of laminated composite and sandwich plates is studied analytically using Navier's technique based on higher order refined theory by Kant and Swaminathan (7). Soltani et al. (8) has analyzed nonlinear tensile behavior of glass fibre reinforced aluminium laminates using finite element modeling. Attallah et al. (9) presented 3- D solutions of laminated composite plates by using a combined finite strip and state space approach. Bharet al. (10) analyzed the significance of the HSDT over the FSDT for laminated composite stiffened plates by using FEM. Grover et al. (11) investigated the static and buckling analysis of laminated composite and sandwich plates in the framework of a new inverse hyperbolic shear deformation theory and this theory is based on shear strain shape function. Kumar et al. (12) studied static analysis of thick skew laminated composite plate with elliptical cutout based on 3-D elasticity theories. Riyah and Ahmed (13 investigated stresses of composite plates with different types of cutouts. Rezaeepazhand and Jafari (14) analytically analyzed the stresses of composite plates with a quasi-square cutout subjected to uniaxial tension based on Lekhnitskii's theory. Static analysis of isotropic rectangular plate with various support conditions and loads are studied by Vanamet al. (15) using finite element analysis (FEA). A recent study detailed the effect of cutout orientation on SCF (16).

Numerical Study of Stress Concentration in a Tensioned Plate

A numerical study using (FEM) has been carried out to investigate the effect of some parameters on the stress concentration factor in a plate, having different types of cutout and subjected to uniaxial tension. These parameters include the location of cutout, orientation of cutout with respect to the axis of loading, radius of bluntness of cutout and the thickness of the plate. Maximum values of stress concentration factor (SCF) were found in cases of: 1. the cutout is in the center of the plate, 2. the angle of a corner of cutout is bisected by an axis perpendicular to the loading axis, 3. the corners of cutout are sharp (zero radius), and 4.the plate is very thin.

Effects of cutouts on natural frequency of laminated composite plates

Abstract In this study, the effects of cutouts (circular, square, triangular and elliptical), cutout position and fiber orientations of laminated composite plates on natural frequencies are investigated. In order to study the effects of cutouts on natural frequencies of the composite plates, experiments have been carried out. Finite element analysis is also performed to predict the effects of different cutouts, cutout position, fiber orientation and length of the plate on natural frequencies for E-glass/polyester. Several outcomes and behavioral characteristics are discussed. These outcomes include the cutout shape, cutout orientation and fiber orientation angle. It has been seen that all of the experimental and finite element results are very close to each other. It has also been concluded that the natural frequency of composite plate is affected by the fiber orientation and cutout location but not considerably affected by cutout shape. The results show that fiber orientation angle and cutout location are the most important parameters on the natural frequency. When the fiber orientation angle increases, both bending and twisting natural frequencies decrease. Maximum natural frequency occurs on [(0/90)4]S laminated plate.