유한 요소법에 의한 크로스-플라이 복합적층판의 해석

송석은,이원홍 진주산업대학교 1998 산업과학기술연구소보 Vol.- No.5

In general, cross-ply laminated compostie plates exhibit properties considerably different from those of the single-layer plate. The great difference in elastic properties between fiber and mtrix materials leads to a higher ratio of in-plane Young`s modulus to transverse shear modulus for laminated composite plates. Thus, to obtain the more accurate solutions to laminated composite plate problems, effcets of shear strain should be considered in analysis of them. The purpose si to expend the first-order shear deformation theory by Finite Element Analysis and to clarify the cross-ply laminated composite plates.

응력장을 이용한 직교적층 탄소섬유/에폭시 복합재 적층판의 모드 I 균열 특성 연구

강민송,전민혁,김인걸,우경식 한국복합재료학회 2019 Composites research Vol.32 No.6

The delamination is a special mode of failure occurring in composite laminates. Several numerical studies with finite element analysis have been carried out on the delamination behavior of unidirectional composite laminates. On the other hand, the fracture for the multi-directional composite laminates may occur not only along the resin-fiber interface between plies known as interply or interlaminar fracture but also within a ply known as interyarn or intralaminar fracture accompanied by matrix cracking and fiber bridging. In addition, interlaminar and intralaminar cracks appear at irregular proportions and intralaminar cracks proceeded at arbitrary angle. The probabilistic analysis method for the prediction of crack growth behavior within a layer is more advantageous than the deterministic analysis method. In this paper, we analyze the crack path when the mode I load is applied to the cross-ply carbon/epoxy composite laminates and collect and analyze the probability data to be used as the basis of the probabilistic analysis in the future. Two criteria for the theoretical analysis of the crack growth direction were proposed by analyzing the stress field at the crack tip of orthotropic materials. Using the proposed method, the crack growth directions of the cross-ply carbon/epoxy laminates were analyzed qualitatively and quantitatively and compared with experimental results. 층간분리는 복합재 적층판에서 발생하는 특수한 파손 모드이다. 유한요소해석기법을 활용하여 균열 성장 방향이 확실히 예측되는 일방향 복합재 적층판의 층간분리 거동과 관련된 많은 수치적 연구가 수행되었다. 반면에 여러 방향으로 적층된 복합재 적층판의 층간분리는 층간 균열 뿐 만 아니라 기지재료 파손 및 섬유 브릿징을 수반하는 층내 균열이 발생한다. 또한 층간 균열과 층내 균열이 불규칙적인 비율로 나타나고 층내 균열도 임의의 각도로 성장한다. 이러한 직교적층 복합재 적층판의 균열 성장 방향에 대한 예측은 확정론적 해석 방법 보다는 확률론적 해석 방법이 유리하다. 본 논문에서는 직교적층 탄소섬유/에폭시 복합재 적층판에 모드 I 하중이 가해질 때 균열 경로를 분석하여 향후 확률론적 해석의 기반 자료로 사용할 수 있는 확률 데이터를 수집하고 분석하였다. 직교이방성 재료의 균열선단에서의 응력장 해석결과를 활용하여 균열 성장 방향을 분석할 수 있는 두 가지 기준을 제안하였다. 제안한 방법을 이용하여 직교적층 탄소섬유/에폭시 복합재 적층판의 균열 성장 방향을 정성적, 정량적으로 분석하고 실험값과 비교분석하였다.

Rate-Dependence of Off-Axis Tensile Behavior of Cross-Ply CFRP Laminates at Elevated Temperature and Its Simulation

Takeuchi, Fumi,Kawai, Masamichi,Zhang, Jian-Qi,Matsuda, Tetsuya The Korean Society for Composite Materials 2008 Advanced composite materials Vol.17 No.1

The present paper focuses on experimental verification of the ply-by-ply basis inelastic analysis of multidirectional laminates. First of all, rate dependence of the tensile behavior of balanced symmetric cross-ply T800H/epoxy laminates with a $[0/90]_{3S}$ lay-up under off-axis loading conditions at $100^{\circ}C$ is examined. Uniaxial tension tests are performed on plain coupon specimens with various fiber orientations $[{\theta}/(90-{\theta})]_{3S}$ ($\theta$ = 0, 5, 15, 45 and $90^{\circ}C$) at two different strain rates (1.0 and 0.01%/min). The off-axis stress.strain curves exhibit marked nonlinearity for all the off-axis fiber orientations except for the on-axis fiber orientations $\theta$ = 0 and $90^{\circ}$, regardless of the strain rates. Strain rate has significant influences not only on the off-axis flow stress in the regime of nonlinear response but also on the apparent off-axis elastic modulus in the regime of initial linear response. A macromechanical constitutive model based on a ply viscoplasticity model and the classical laminated plate theory is applied to predictions of the rate-dependent off-axis nonlinear behavior of the cross-ply CFRP laminate. The material constants involved by the ply viscoplasticity model are identified on the basis of the experimental results on the unidirectional laminate of the same carbon/epoxy system. It is demonstrated that good agreements between the predicted and observed results are obtained by taking account of the fiber rotation induced by deformation as well as the rate dependence of the initial Young's moduli.

Elastic stresses and failure of rotating cross-ply laminate disks

구교남 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.5

Centrifugal force acting on a rotating disk induces in-plane loads in the radial and circumferential directions. An application of fiber-reinforced composite materials to a rotating disk can satisfy the demand for increasing its rotating speed. However, previous researches have been confined to single lamina disks. In this paper, a stress analysis of rotating disks made of multidirectional laminates is performed. The Tsai-Wu failure criterion is applied to the strength analysis of the rotating laminate disks, from which the maximum allowable speeds are obtained. The cross-ply ratios providing the maximum allowable speeds are obtained for the glass/epoxy and carbon/epoxy cross-ply laminate disks with CD geometry.

광섬유 A-EFPI 센서를 이용한 직교적층 복합재료의 표피층 및 내부층의 변형률 해석

우성충 ( Sung Choong Woo ),박래영 ( Lai Young Park ),최낙삼 ( Nak Sam Choi ),권일범 ( Il Bum Kwon ) 한국복합재료학회 2004 Composites research Vol.17 No.5

Curvature tailoring of unsymmetric laminates with an initial curvature

Ryu, Junghyun,Kong, Jung-Pyo,Kim, Seung-Won,Koh, Je-Sung,Cho, Kyu-Jin,Cho, Maenghyo SAGE Publications 2013 Journal of composite materials Vol.47 No.25

<P>An unsymmetric laminated composite having bi-stability is interesting as a morphing structure because it can sustain large deformation without energy supply and the deformed state is stable. Especially, inducing different curvature values at each stable state is important for the practical application of unsymmetric laminates. In this study, we propose a method for tailoring the curvature of unsymmetric cross-ply laminates by curing the composite on a curved tool plate. The results show that the final normal curvature tensor of unsymmetric laminates is the summation of the tool plate curvature tensor and the normal curvature tensor of the laminates.</P>

A new refined hyperbolic shear deformation theory for laminated composite spherical shells

Kada Draiche,Abdelouahed Tounsi 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.6

In this study, a new refined hyperbolic shear deformation theory (RHSDT) is developed using an equivalent singlelayer shell displacement model for the static bending and free vibration response of cross-ply laminated composite spherical shells. It is based on a new kinematic in which the transverse displacement is approximated as a sum of the bending and shear components, leading to a reduction of the number of unknown functions and governing equations. The proposed theory uses the hyperbolic shape function to account for an appropriate distribution of the transverse shear strains through the thickness and satisfies the boundary conditions on the shell surfaces without requiring any shear correction factors. The shell governing equations for this study are derived in terms of displacement from Hamilton’s principle and solved via a Navier-type analytical procedure. The validity and high accuracy of the present theory are ascertained by comparing the obtained numerical results of displacements, stresses, and natural frequencies with their counterparts generated by some higher-order shear deformation theories. Further, a parametric study examines in detail the effect of both geometrical parameters (i.e., side-to-thickness ratio and curvature-radius-to-side ratio), on the bending and free vibration response of simply supported laminated spherical shells, which can be very useful for many modern engineering applications and their optimization design.

Analysis of Longitudinal Strains of Cross-ply Composite Laminates using A-EFPI Optical Fiber Sensor

Woo, Sung-Choong,Choi, Nak-Sam,Kwon, Il-Bum,Rhee, Kyong Y. Sage Publications 2007 Journal of composite materials Vol.41 No.7

<P>The longitudinal strains (U03B5;<SUB>x</SUB>) of the core and the skin layers in glass fiber reinforced plastic (GFRP) cross-ply composite laminates are analyzed using embedded optical fiber sensors (OFSs) of absolute extrinsic FabryU2014;Perot interferometer (A-EFPI). Foil-type strain gages (SGs) bonded on both upper and lower surfaces of a specimen are employed for comparison of the strain measurement on the surface. It has been shown that the values of U03B5;<SUB>x</SUB> in the interior of the skin layer and the core layer measured by embedded A-EFPI sensor are lower than those of the specimen surface measured by SGs. Experimental results agree well with those from finite element analysis based on a shear lag model. Optical microscopy observation of the damage behavior around the fiber sensor by the thin-sectioning technique shows that reinforcing glass fibers protect the OFS embedded in the 0<SUP> U00B0;</SUP> skin layer, whereas the formation of transverse cracks in the 90<SUP> U00B0;</SUP> core layer substantially reduces strains at the failure of OFS embedded in the core layer.</P>

ANALYSIS OF A LAMINATED COMPOSITE WIND TURBINE BLADE CHARACTERISTICS THROUGH MATHEMATICAL APPROACH

최영도,고재귀,김석찬 한국산업응용수학회 2019 Journal of the Korean Society for Industrial and A Vol.23 No.4

A 1kW-class horizontal axis wind turbine (HAWT) rotor blade is taken into ac-count to investigate elastic characteristics in 2-D. The elastic blade field is composed of symmetric cross-ply laminated composite material. Blade element momentum theory is applied to obtain the boundary conditions pressuring the blade, and the plane stress elasticity problem is formulated in terms of two displacement parameters with mixed boundary conditions. For the elastic characteristics a fair of differential equations are derived based on the elastic theory. The domain is divided by triangular and rectangular elements due to the complexity of the blade configuration, and a finite element method is developed for the governing equations to search approximate solutions. The results describe that the elastic behavior is deeply influenced by the layered angle of the middle laminate and the stability of the blade can be improved by control-ling the layered angle of laminates, which can be evaluated by the mathematical approach.

복합적층 회전원판의 응력 및 진동 해석

구교남(Koo, Kyo-Nam) 한국소음진동공학회 2006 한국소음진동공학회 논문집 Vol.16 No.9

The centrifugal force acting on a rotating disk creates the in-plane loads in radial and circumferential directions. Application of fiber reinforced composite materials to the rotating disk can satisfy the demand for the increment of its rotating speed. However, the existing researches have been confined to lamina disks. This paper deals with the stress and vibration analysis of rotating laminated composite disks. The maximum strain theory for failure criterion is applied to determine the strength of the laminate disk from which the maximum allowable speed is obtained. Dynamic equation is formulated in order to calculate the natural frequency and critical speed for rotating laminated disks. The Galerkin method is applied to obtain the series solution. The numerical results are given for the cross-ply laminated composite disks.