• Advances in nano research
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• 제14권2호
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• pp.141-154
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• 2023

Effects of viscoelastic foundation on vibration of curved-beam structure with clamped and simply-supported boundary conditions is investigated in this study. In doing so, a micro-scale laminate composite beam with two piezoelectric face layer with a carbon nanotube reinforces composite core is considered. The whole beam structure is laid on a viscoelastic substrate which normally occurred in actual conditions. Due to small scale of the structure non-classical elasticity theory provided more accurate results. Therefore, nonlocal strain gradient theory is employed here to capture both nano-scale effects on carbon nanotubes and microscale effects because of overall scale of the structure. Equivalent homogenous properties of the composite core is obtained using Halpin-Tsai equation. The equations of motion is derived considering energy terms of the beam and variational principle in minimizing total energy. The boundary condition is assumed to be clamped at one end and simply supported at the other end. Due to nonlinear terms in the equations of motion, semi-analytical method of general differential quadrature method is engaged to solve the equations. In addition, due to complexity in developing and solving equations of motion of arches, an artificial neural network is design and implemented to capture effects of different parameters on the inplane vibration of sandwich arches. At the end, effects of several parameters including nonlocal and gradient parameters, geometrical aspect ratios and substrate constants of the structure on the natural frequency and amplitude is derived. It is observed that increasing nonlocal and gradient parameters have contradictory effects of the amplitude and frequency of vibration of the laminate beam.

• 대한기계학회논문집A
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• 제41권10호
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• pp.959-965
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• 2017

최근 선진항공사에서는 항공기 복합재 구조의 변형률을 평가할 때 적층판 파손이론을 사용한다. 적층판 파손이론은 복합재 구조평가에 적층판의 파손변형률을 사용한다. 본 논문은 적층판 인장파손특성의 시험적 평가 절차를 보여준다. 시험적 평가는 회귀분석법(regression analysis method)을 사용하였다 회귀분석은 적층판의 파손변형률을 응답변수로 하고 적층판 내 $0^{\circ}$, ${\pm}45^{\circ}$층의 비율을 회귀변수로 하는 방법이다. 본 논문에 사용된 복합재료는 $177^{\circ}C(350^{\circ}F)$에서 경화되는 Carbon/Epoxy UD Tape 프리프레그이다. 시편은 $0^{\circ}$, $+45^{\circ}$, $-45^{\circ}$ 및 $90^{\circ}$층으로 적층된 14 종류의 노치없는 적층판으로 총 149개 시편으로 구성하였다. 시험방법은 ASTM-D-3039 규정을 사용하였다.

• 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.

• 전산구조공학
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• 제7권4호
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• pp.103-111
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• 1994

앞의 논문 Part 1 에서 유도한 변분원리를 이용하여 복합재료적층판의 진동해석을 할 수 있는 유한요소해석 모델을 개발하였다. 이 모델에서는 어느 한 층의 면내 변위와 나머지층 단면의 회전각, 그리고 판 전체의 연직방향처짐을 절점변수로 취하게 되어 n개층으로된 적층판의 경우 2(n+1)+1의 절점 자유도를 갖는다. 따라서, 판의 주변에서는 한층의 면내변위와 각층단면의 회전각을, 판의 면내에서는 연직방향 처짐을 경계조건값으로 정의할 수 있다. 이 모델에 의해 개발한 프로그램을 이용하여 각층의 재료특성이 크게 다른 혼종형 복합재료적층판(hybrid laminate)의 고유진동문제를 해석하였다. 탄성이론해 및 다른 유한요소해석결과와 본 해석결과와의 비교를 통해 제시모델이 기존의 다른 유한요소모델보다 정확함을 예시하였다.

• 대한기계학회논문집
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• 제15권1호
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• pp.28-40
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• 1991

본 연구에서는 4변이 단순 지지된 두꺼운 역대칭 앵글 플라이 적층판의 굽힘, 좌굴 및 진동 거동을 규명하였으며, 인장과 굽힘, 비틀림 사이의 결합 특성을 고려하 였고, 전단 변형을 고려하였다.또 유사 변환 개념을 도입하여 복합 재료 적층판의 거동을 일반화 하였다.

• 한국생산제조학회지
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• 제21권4호
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• pp.608-612
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• 2012

To reduce these costs and time by finite element analysis program has been much research (3~4). At virtual CAE program as like Abaques, Ansys, Ls-dyna and Nastran, the input data of material is got bellow coupon test. In case of carbon composite, it is also put in lamina/laminate properties. There have big problem. If you want to simulate FW(filament winding or wind blade) how do you input material data. Each area of FW is different stacking conditions. It's too hard that each area is tested for inputting lamina or laminate properties. The composite structure increasing load is applied occurred as the matrix dependence of the crack-induced nonlinearity and nonlinear mobility appears since the initial damage. And uni-direction for this research applies the theory to have been confined to. On this study, we are going to get basically fiber properties and matrix than carbon composite properties for simulating according stacking method by GENOA-MCQ. It is help to simulate easily composite material. Also Calculate the matrix nonlinear for simulating non-linear.

• Structural Engineering and Mechanics
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• 제5권4호
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• pp.433-450
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• 1997

The objective of this work is to predict the failure loads, associated maximum transverse displacements, locations and the modes of failure, including the onset of delamination, of thin, flat, square symmetric laminates under the action of uni-axial compression. Two progressive failure analyses, one using Hashin criterion and the other using Tensor polynomial criteria, are used in conjunction with the finite element method. First order shear deformation theory and geometric nonlinearity in the von Karman sense have been employed. Five different types of lay-up sequence are considered for laminates with all edges simply supported. In addition, two boundary conditions, one with all edges fixed and other with mixed boundary conditions for $(+45/-45/0/90)_{2s}$ quasi-isotropic laminate have also been considered to study the effect of boundary restraints on the failure loads and the corresponding modes of failure. A comparison of linear and nonlinear results is also made for $({\pm}45/0/90)_{2s}$ quasi-isotropic laminate. It is observed that the maximum difference between the failure loads predicted by various criteria depend strongly on the laminate lay-ups and the flexural boundary restraints. Laminates with clamped edges are found to be more susceptible to failure due to the transverse shear and delamination, while those with the simply supported edges undergo total collapse at a load slightly higher than the fiber failure load.

• 한국공작기계학회논문집
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• 제12권4호
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• pp.43-49
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• 2003

This research work has been carried out for finding J-integral in mode II of CFRP(carbon fiber reinforced plastics) laminate plates based on the classical bar theory in dynamic conditions with consideration of the effect of inertia forces, eventually to lead to finding the dynamic inter-layer fracture toughness. Dynamic inter-layer fracture toughness was found by a self-made ENF(End Notched Flexure) experimental apparatus using Split Hopkinson's Bar(SHPB), and also observed the variation of the fracture toughness haying different resin contents and fiber arrangements of CFRP specimen([$0_3^{\circ}/90_3^{\circ}/0_6^{\circ}/90_3^{\circ}/0_3^{\circ}$], [$0_{20}^{\circ}$], [$0_5^{\circ}/90_{10}^{\circ}/0_5^{\circ}$]). As an experimental result, in either cases of quasi-static or dynamic load condition, the critical load and the inter-layer fracture toughness increased sharply depending on the increase of resin contents. Therefore, it could, be concluded that the effect by resin contents is the major factor determining the inter-layer fracture toughness in the CFRP laminate plates.

• Steel and Composite Structures
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• 제50권2호
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• pp.183-199
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• 2024

In this paper, a closed-form rigorous solution for interfacial stress in continuous steel beam with variable section strengthened with bonded prestressed FRP plates and subjected to a uniformly distributed load is developed using linear elastic theory and including the variation of fiber volume fractions with a longitudinal orientation of the fibers of the FRP plates. The results show that there exists a high concentration of both shear and normal stress at the ends of the laminate, which might result in premature failure of the strengthening scheme at these locations. The theoretical predictions are compared with other existing solutions. Overall, the predictions of the different solutions agree closely with each other. A parametric study has been conducted to investigate the sensitivity of interface behavior to parameters such as laminate and adhesive stiffness, the thickness of the laminate and the fiber volume fractions where all were found to have a marked effect on the magnitude of maximum shear and normal stress in the composite member. This research gives a numerical precision in relating to the others studies which neglect the effect of prestressed plate and the shear lag impact. The physical and geometric properties of materials are taken into account, and that may play an important role in reducing the interfacial stresses magnitude.

• Composites Research
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• 제16권4호
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• pp.1-9
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• 2003

타이어 벨트층의 층간거동을 모사하기 위하여 2층 복합적층판을 고려하였다. 벨트층내의 층간전단응력 및 변형률을 측정하기위하여 3차원 유한요소해석을 수행하였다. 폭방향 전단변형률은 핀 이용법을 활용하여 측정되었다. 이들 실험 측정값은 적층판의 중앙부에서는 고전적층판이론과 그리고, 양가장자리부에서는 Kassapoglou 및 Kelsey의 이혼과 비교 하였다. 고무는 선형탄성체의 가정하였으며. 고투/코드 복한적층판은 직교이방성재질로 단순화 하였다 해석결과로부터, 층간박리의 원인인 층간전단응력은 고무내부의 양가장자리부에서 가장 큰 값을 보였다. 결과값은 중앙영역에서 고전적 층판이론과 매우 잘 일치하였으며. 양가장자리부에서는 이론값들과는 다소 차이를 보였다.