• Structural Engineering and Mechanics
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• v.72 no.4
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• pp.433-441
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• 2019

In this paper, geometrically nonlinear static analysis of laminated composite beams is investigated under hygrothermal effect. In the solution of problem, the finite element method is used within the first shear beam theory. Total Lagrangian approach is used nonlinear kinematic model. The geometrically nonlinear formulations are developed for the laminated beams with hygro-thermal effects. In the nonlinear solution of the problem, the Newton-Raphson method is used with incremental displacement. In order to verify of obtained formulations, a comparison study is performed. The effects of the fiber orientation angles, the stacking sequence of laminates, temperature rising and moisture changes on the nonlinear static displacements and configurations of the composite laminated beam are investigated in the numerical results.

• Structural Engineering and Mechanics
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• v.77 no.2
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• pp.245-259
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• 2021

In this research, the influence of the laminate stacking sequence on thermal stress distribution in symmetric composite plates with a quasi-square cutout subjected to uniform heat flux is examined analytically using the complex variable technique. The analytical solution is obtained based on the thermo-elastic theory and the Lekhnitskii's method. Furthermore, by employing a suitable mapping function, the solution of symmetric laminates containing a circular cutout is extended to the quasi-square cutout. The effect of important parameters including the stacking sequence of laminates, the angular position, the bluntness, the aspect ratio of cutout, the flux angle and the composite material are examined on the thermal stress distribution. It is found out that the circular shape for cutout may not necessarily be the optimum geometry for all stacking sequences. The finite element analysis results are used to validate the analytical solution.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.74-78
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• 2003

Stress analysis was conducted with finite element method to study the stress distributions in both single-pin and multi-pin loaded composite laminates. The various parameters involved in the design of the joint method were considered. The stress distributions in the vicinity of the holes were predicted considering the effects of various parameters such as the lay-ups, number of pins, number of rows, row spacing, and hole patterns. The results show that the performance of joint is greatly affected by these parameters.

• Journal of Theoretical and Applied Mechanics
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• v.3 no.1
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• pp.45-65
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• 2002

A constitutive model on oorthotropic thermo-elasto-viscoplasticity for fiber-reinforced composite materials Is illustrated, and their thermomechanical responses are predicted with the fully-coupled finite element formulation. The unmixing-mixing scheme can be adopted with the multipartite matrix method as the constitutive model. Basic assumptions based upon the composite micromechanics are postulated, and the strain components of thermal expansion due to temperature change are included In the formulation. Also. more than two sets of mechanical variables, which represent the deformation states of multipartite matrix can be introduced arbitrarily. In particular, the unmixing-mixing scheme can be used with any well-known isotropic viscoplastic theory of the matrix material. The scheme unnecessitates the complex processes for developing an orthotropic viscoplastic theory. The governing equations based on fully-coupled thermomechanics are derived with constitutive arrangement by the unmixing-mixing concept. By considering some auxiliary conditions, the Initial-boundary value problem Is completely set up. As a tool of numerical analyses, the finite element method Is used with isoparametric Interpolation fer the displacement and the temperature fields. The equation of mutton and the energy conservation equation are spatially discretized, and then the time marching techniques such as the Newmark method and the Crank-Nicolson technique are applied. To solve the ultimate nonlinear simultaneous equations, a successive iteration algorithm is constructed with subincrementing technique. As a numerical study, a series of analyses are performed with the main focus on the thermomechanical coupling effect in composite materials. The progress of viscoplastic deformation, the stress-strain relation, and the temperature History are careful1y examined when composite laminates are subjected to repeated cyclic loading.

• Structural Engineering and Mechanics
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• v.63 no.5
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• pp.597-605
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• 2017

Our work aims to analyze using the finite element method the evolution of the stress intensity factor (SIF) parameter K of three laminated folded plates stacks [$+{\alpha}$, $-{\alpha}$], made of the same epoxy matrix and different reinforcement fibers (boron, graphite and glass). Our results show that the angle of orientation of the boron/epoxy composite has no great influence on the variation of the parameter KI. Compared to composite graphite/epoxy and glass/epoxy, the laminated composite boron/epoxy reduces more the SIF KI in the middle of the plate for angles $0^{\circ}{\leq}{\alpha}{\leq}30^{\circ}$.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.191-194
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• 2001

A partially coupled thermo-piezoelectric-mechanical triangular finite element model of composite laminates with surface bonded piezoelectric actuators, subjected to externally applied mechanical load, temperature change load, electric field load is developed. The governing differential equations are obtained by applying the principle of free energy and variational techniques. A higher order zigzag theory displacement field is employed to accurately capture the transverse shear and normal effects in laminated composite plates of arbitrary thickness. Nonconforming shape functions by Specht are employed in the transverse displacement variables. Numerical examples demonstrate the accuracy and efficiency of the proposed triangular plate element.

• The KSFM Journal of Fluid Machinery
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• v.11 no.4
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• pp.22-31
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• 2008

In this study, computer applied engineering (CAE) techniques are fully used to conduct structural and dynamic analyses of a huge composite rotor blade. Computational fluid dynamics is used to predict aerodynamic load of the rotating wind-turbine blade model. Static and dynamic structural analyses are conducted based on finite element method for composite laminates and multi-body dynamic simulation tools. Various numerical results for aerodynamic load, static stress, buckling and dynamic analyses are presented and characteristics of structural behaviors are investigated herein.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.3
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• pp.360-369
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• 2015

A methodology for determining the design allowables of composite laminates by using lamina level test data and finite element analysis (FEA) is proposed and verified in this paper. An existing method that yields the laminate design allowables by using the complete test results for laminates was improved to reduce the expensive and time-consuming tests. Input property samples for FEA were generated after considering the statistical distribution characteristics of lamina level test data., and design allowables were derived from several FEA analyses of laminates. To apply and verify the proposed method, Hexcel 8552 IM7 test data were used. For both un-notched and open-hole laminate configurations, it was found that the design allowables obtained from the analysis correctly predicted the laminate test data within the confidence interval. The potential of the present simulation to substitute the laminate tests was demonstrated well.

• Steel and Composite Structures
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• v.13 no.3
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• pp.207-223
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• 2012

This paper deals with critical thermal buckling load optimization of symmetrically laminated four layered angle-ply plates with one or two different intermediate line supports. The design objective is the maximization of the critical thermal buckling load and a design variable is the fibre orientation in the layers. The first order shear deformation theory and nine-node isoparametric finite element model are used for the finite element solution of the laminates. The modified feasible direction (MFD) method is used for the optimization routine. For this purpose, a program based on FORTRAN is used. Finally, the numerical analysis is carried out to investigate the effects of location of the internal line supports, plate aspect ratios and boundary conditions on the optimal designs and the results are compared.

• Steel and Composite Structures
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• v.37 no.4
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• pp.419-429
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• 2020

Composite structures are generally pressurized at both sides when repaired by the scarf repair method. But single-face vacuum bag curing (SVC) may be used in some practical scarf repair of penetration damage due to the low accessibility of composite structures, which can decrease bonding quality and may reduce structural mechanical properties. In this paper, experimental investigations were conducted on tensile and compressive properties of scarf-repaired composite laminates using SVC and double-face vacuum bag curing (DVC) in four hygrothermal environments. Finite element models of composite scarf joints with voids were established to further explore the failure mechanism of scarf-repaired laminates. Results show that the curing condition hardly affects tensile and compressive properties of the repaired laminates though it significantly affects the bonding quality with adhesive inner voids. Failure loads of scarf joints almost keep unchanged with adhesive voids increasing.