• Structural Engineering and Mechanics
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• 제33권6호
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• pp.657-674
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• 2009

In this paper a 3-D continuum damage mechanics formulation for composite laminates and its implementation into a finite element model that is based on the layer-wise laminate plate theory are described. In the damage formulation, each composite ply is treated as a homogeneous orthotropic material exhibiting orthotropic damage in the form of distributed microscopic cracks that are normal to the three principal material directions. The progressive damage of different angle ply composite laminates under quasi-static loading that exhibit the free edge effects are investigated. The effects of various numerical modeling parameters on the progressive damage response are investigated. It will be shown that the dominant damage mechanism in the lay-ups of [+30/-30]s and [+45/-45]s is matrix cracking. However, the lay-up of [+15/-15] may be delaminated in the vicinity of the edges and at $+{\theta}/-{\theta}$ layers interfaces.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.1-4
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• 2001

A new non-destructive fatigue prediction model of the composite laminates is developed. The natural frequencies of fatigue-damaged laminates under extensional loading are related to the fatigue lift of the laminates by establishing the equivalent flexural stiffness reduction as a function of the elastic properties of sublaminates. The flexural stiffness is derived by relating the $90^{\circ}$-ply elastic modulus reduction, and using the laminate plate theory to the degraded elastic modulus and the intact elastic modulus of other laminate. The natural frequency reduction model, in which the dominant fatigue mode can be identified from the sensitivity scale factors of sublaminate elastic properties, provides natural frequency vs. fatigue cycle curves for the composite laminates. Vibration tests were also conducted on $[\textrm{90}_{2}\textrm{0}_{2}]_s$ carbon/epoxy laminates to verify the natural frequency reduction model. Correlations between the predictions of the model and experimental results are good.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1994년도 가을 학술발표회 논문집
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• pp.121-128
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• 1994

A layerwise theory for the dynamic response of a laminated composite plate with integrated piezoelectric actuators and sensors subjected to both mechanical and electrical loadings is proposed. The formulation is derived form the variational principle with consideration for both total potential energy of the structures and the electrical potential energy of the piezoceramics. The governing equations of the present theory account for direct and converse effects of piezoelectrics, and layerwise variation of displacement field through the thickness of a laminate.

• Journal of Mechanical Science and Technology
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• 제19권4호
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• pp.947-957
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• 2005

In this study a simple model is developed that predicts impact damage in a composite laminate avoiding the need of the time-consuming dynamic finite element method (FEM). The analytical model uses a non-linear approximation method (Rayleigh-Ritz) and the large deflection plate theory to predict the number of failed plies and damage area in a quasi-isotropic composite circular plate (axisymmetric problem) due to a point impact load at its centre. It is assumed that the deformation due to a static transverse load is similar to that oc curred in a low velocity impact. It is found that the model, despite its simplicity, is in good agreement with FEM predictions and experimental data for the deflection of the composite plate and gives a good estimate of the number of failed plies due to fibre breakage. The predicted damage zone could be used with a fracture mechanics model developed by the second investigator and co-workers to calculate the compression after impact strength of such laminates. This approach could save significant running time when compared to FEM solutions.

• Structural Engineering and Mechanics
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• 제52권4호
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• pp.815-827
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• 2014

Buckling optimization of laminated composite plates is significant as they fail because of buckling under in-plane compressive loading. The plate is usually modeled without cutout so that the buckling strength is found analytically using classical laminate plate theory (CLPT). However in real world applications, the composite plates are modeled with cutouts for getting them assembled and to offer the provisions like windows, doors and control system. Finite element analysis (FEA) is used to analyze the buckling strength of the plate with cutouts and it leads to high computational cost when the plate is optimized. In this article, a genetic algorithm based optimization technique is used to optimize the composite plate with cutout. The computational time is highly reduced by replacing FEA with artificial neural network (ANN). The effectiveness of the proposed method is explored with two numerical examples.

• Structural Engineering and Mechanics
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• 제22권3호
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• pp.331-349
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• 2006

The stresses and deflections in a laminated rectangular plate under thermal vibration are determined by using the moving least squares differential quadrature (MLSDQ) method based on the first order shear deformation theory. The weighting coefficients used in MLSDQ approximation are obtained through a fast computation of the MLS shape functions and their partial derivatives. By using this method, the governing differential equations are transformed into sets of linear homogeneous algebraic equations in terms of the displacement components at each discrete point. Boundary conditions are implemented through discrete grid points by constraining displacements, bending moments and rotations of the plate. Solving this set of algebraic equations yields the displacement components. Then substituting these displacements into the constitutive equation, we obtain the stresses. The approximate solutions for stress and deflection of laminated plate with cross layer under thermal load are obtained. Numerical results show that the MLSDQ method provides rapidly convergent and accurate solutions for calculating the stresses and deflections in a multi-layered plate of cross ply laminate subjected to thermal vibration of sinusoidal temperature including shear deformation with a few grid points.

• Journal of Advanced Marine Engineering and Technology
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• 제25권3호
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• pp.617-622
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• 2001

The purpose of this study is to design and the analyze the stress of composited shaft which is wound by filament winding method. The composites shaft has high strength and reduction in weight compared to metal shaft. The classical laminate plate theory(CLT) was used fro analysis the stress, and for structure design. In order to replace metal shaft by composites shaft, the diameter of shaft was determined to $\phi$ 40. The ration of diameter was determined to 0.4 for torsional moment with CLT. In this result of analyzing the stress, composites shaft was safe $30^{\circ}~60^{\circ}$C of winding angle, and was fractured on $90^{\circ}$.

• Structural Engineering and Mechanics
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• 제6권6호
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• pp.583-612
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• 1998

A unified third-order laminate plate theory that contains classical, first-order and third-order theories as special cases is presented. Analytical solutions using the Navier and L$\acute{e}$vy solution procedures are presented. The Navier solutions are limited to simply supported rectangular plates while the L$\acute{e}$vy solutions are restricted to rectangular plates with two parallel edges simply supported and other two edges having arbitrary combination of simply supported, clamped, and free boundary conditions. Numerical results of bending and vibration for a number of problems are discussed in the second part of the paper.

• 대한기계학회논문집
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• 제17권7호
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• pp.1686-1699
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• 1993

In this paper, the thermal buckling of thick composite angle-ply laminates subject to uniform temperature distribution is studied. For the plates of 4-edges simply supported condition and those of 4-edges clamped condition, the critical buckling temperatue is derived, using tile finite element method based on the shear deformation theory. The effects of lamination angle, layer number, laminate thickness, plate aspect ratio and boundary constraints upon the critical buckling temperature are presented.

• Structural Engineering and Mechanics
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• 제31권5호
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• pp.587-603
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• 2009

We performed a free vibration analysis of skew composite laminates with or without cutout based on the high-order shear deformation plate theory (HSDT). The effects of skew angles and ply orientations on the natural frequencies for various boundary conditions are studied using a nonlinear high-order finite element program developed for this study. The numerical results are in good agreement with those reported by other investigators for simple test cases, and the new results reported in this paper show the interactions between the skew angle, layup sequence and cutout size on the free vibration of the laminate. The findings highlight the importance of skew angles when analyzing laminated composite skew plates with cutout or without cutout.