• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
• /
• pp.175-183
• /
• 2000

The internal residual stresses within the multilayered structure with shan interface induced by the difference in thermal expansion coefficient between the materials of adjacent layers often provide the source of failure such as delamination of interfaces and etc. Recent development of the multilayered structure with functionally graded interface would be the solution to prevent this kind of failure. However a systematic thermo-mechanical analysis is needed fur the customized structural design of multilayered structure. In this study, theoretical model for the thermo-mechanical analysis is developed for multilayered structures of the Al-$SiC_p$ functionally graded composite for electronic packaging. The evolution of curvature and internal stresses in response to temperature variations is presented for the different combinations of geometry. The resultant analytical solutions are used for the optimal design of the multilayered structures with functionally graded interface as well as with sharp interface.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
• /
• pp.224-227
• /
• 2001

Adaptive analysis of multilayered composite and sandwich plates is carried out. The adaptive analysis is based on a finite element error form, which measures the difference between the through-the-thickness distribution of finite element displacement and the actual displacement. The region where the error-measure exceeds the prescribed admitted error value, the finite element mesh locally refined in the thickness direction using the mesh superposition technique. Several numerical tests are conducted to validate the effectiveness of the current approach for adaptive analysis of laminated plates.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
• /
• pp.89-92
• /
• 2000

In this paper, an effective procedure is presented for the local recovery of displacements and stresses in multilayered composite panels, which incorporate the local refinement using mesh superposition. The mesh superposition method is used to refine the global coarse mesh by superimposing refined mesh to the localized zone of interest without transition zones. The finite element model used is a solid element based on the Hellinger-Reissner variational principle. The a posteriori computation of the through-the-thickness distributions of displacements and stresses is achieved using a predictor-corrector procedure. The procedure utilizes the superconvergent stresses and nodal displacements of the finite element patch. The element patch is generated by locally superimposing a refined local mesh to the coarse global mesh.

• Advanced Composite Materials
• /
• 제18권2호
• /
• pp.153-166
• /
• 2009

A matrix method for evaluating effective electro-magneto-thermo-elastic properties of a generally anisotropic multilayered composite is presented. Physical variables are categorized into two groups: one that satisfies the continuity across the interface between layers and another that satisfies an average inter-layer compatibility (which is also exact). The coupled electro-magneto-thermo-elastic constitutive equation is accordingly reassembled into submatrices, which leads to the derivation of concise and exact matrix expressions for effective properties of a multilayered composite having the coupled physical effects. Comparing the results for a purely elastic multiplayer with those from other theoretical approaches validates the developed method. Examples are given for a PZT-graphite/epoxy composite and a $BaTiO_3-CoFe_2O_4$ multiplayer which exhibit piezo-thermoelastic and magnetoelectric properties, respectively. The result shows how a strong magnetoelectric effect can be achieved by combining piezoelectric and piezomagnetic materials in a multilayered structure. The magnetoelectric coefficient of the $BaTiO_3-CoFe_2O_4$ multiplayer is compared with those for fibrous and particulate composites fabricated with the same constituents.

• Composites Research
• /
• 제13권6호
• /
• pp.23-29
• /
• 2000

층상구조재료가 갖는 약점으로는 구성재료층 간의 열.기계적 특성 차이로 인하여 내부응력이 발생되고 비틀림 변형이 유발되어 형상 제어가 매우 어려울 뿐만 아니라, 반복적인 열 하중으로 인해 열이력을 받을 경우 접합부에서의 파손이 생길 수 있다는 것이다. 최근 층상구조에서 조직 혹은 조성이 점차적으로 변하는 계면을 삽입한 경사조성재료는 열.기계적 변형특성 차이에 의한 재료의 손상을 최소화시킬 수 있으나, 용도에 적합한 구조설계를 위해서 열.기계적 해석이 필요하다. 본 연구에서는 전자패키징용 $Al-SiC_p$ 경사조성 복합재료의 기하학적 구조와 온도변화에 따른 곡면화 변형 및 내부응력분포를 해석하고자 하였다. 한편 층상구조 $Al-SiC_p$ 경사조성 복합재료의 열변형량을 측정하고 내부응력분포를 실험적으로 구하여, 이론적으로 계산한 결과와 비교하였다. 본 연구의 해석결과는 경사조성 층상구조재료의 최적구조 설계에 유용하게 적용할 수 있다.

• 한국해양공학회지
• /
• 제10권4호
• /
• pp.92-102
• /
• 1996

In this research, to develope the A1 7075/CFRP multilayered hybrid composites, CRALL(Carbon Reinforced aluminum lamiate) specimens were processed by autoclavecuring system that curing temperature, time, surface pretreatment condition of aluminum were constant. Andthe fatigye life and failure mechanism on CFRP volume fraction and fiber orientation of CRALLspecimens were investigated. A fatigue life was greatly influenced by effect of CFRP fiber volume fraction but it was less effected than those of fiber orientation. The fatigue failure arised from interface delamination of CFRP and aluminum sheet after shear fracture of aluminum layer. The failure mechanism is assumed that the aluminum laminates which divide the CFRP into many thim layers tend to arrest the failure propagation.

• 한국진공학회지
• /
• 제6권S1호
• /
• pp.80-88
• /
• 1997

The attempt to enhance the strength of materials has been an important subject for materials engineering and scientists. The strength of materials is termed as the ability to support high load without excessive deformation and without breaking catastrophically. The control of dislocation densities and barriers to the movement of dislocations have been considered to be the important methods for the strengthening materials. One of the approaches is mechanical blocking of dislocations by alternately depositing material layers. The typical structure of materials is multilayered and laminated composites. The thickness of each layer is typically in the range of nanometer. Ton avoid confusion with other terminology they may be defined as microlaminate composite materials. The manufacturing process of multilayered laminate structure will be introduced. And the current theoretical theories will be reviewed in view of strengthening of microlaminte composite materials.

• Steel and Composite Structures
• /
• 제31권3호
• /
• pp.277-290
• /
• 2019

This paper investigates the parametric instability (PI) of multilayered composite conical shells (MLCCSs) under axial load periodically varying the time, using the first order shear deformation theory (FOSDT). The basic equations for the MLCCSs are derived and then the Galerkin method is used to obtain the ordinary differential equation of the motion. The equation of motion converted to the Mathieu-Hill type differential equation, in which the DI is examined employing the Bolotin's method. The expressions for left and right limits of dimensionless parametric instability regions (PIRs) of MLCCSs based on the FOSDT are obtained. Finally, the influence of various parameters; lay-up, shear deformations (SDs), aspect ratio, as well as loading factors on the borders of the PIRs are examined.

• 한국세라믹학회지
• /
• 제51권5호
• /
• pp.435-441
• /
• 2014

Silicon carbide-based ceramics and their composites have been studied for application to fusion and advanced fission energy systems. For fission reactors, $SiC_f$/SiC composites can be applied to core structural materials. Multilayered SiC composite fuel cladding, owing to its superior high temperature strength and low hydrogen generation under severe accident conditions, is a candidate for the replacement of zirconium alloy cladding. The SiC composite cladding has to retain its mechanical properties and original structure under the inner pressure caused by fission products; as such it can be applied as a cladding in fission reactor. A hoop strength test using an expandable polyurethane plug was designed in order to evaluate the mechanical properties of the fuel cladding. In this paper, a hoop strength test of the multilayered SiC composite tube for nuclear fuel cladding was simulated using FEA. The stress caused by the plug was distributed nonuniformly because of the friction coefficient difference between the inner surface of the tube and the plug. Hoop stress and shear stress at the tube was evaluated and the relationship between the concentrated stress at the inner layer of the tube and the fracture behavior of the tube was investigated.

• Smart Structures and Systems
• /
• 제9권2호
• /
• pp.105-125
• /
• 2012

A modified Pagano method is developed for the three-dimensional (3D) free vibration analysis of simply-supported, multilayered functionally graded material (FGM) circular hollow cylinders with a constant rotational speed with respect to the meridional direction of the cylinders. The material properties of each FGM layer constituting the cylinders are regarded as heterogeneous through the thickness coordinate, and then specified to obey a power-law distribution of the volume fractions of the constituents, and the effects of centrifugal and Coriolis accelerations, as well as the initial hoop stress due to rotation, are considered. The Pagano method, which was developed for the static and dynamic analyses of multilayered composite plates, is modified in that a displacement-based formulation is replaced by a mixed formulation, the complex-valued solutions of the system equations are transferred to the real-valued solutions, a successive approximation method is adopted to extend its application to FGM cylinders, and a propagator matrix method is developed to reduce the time needed for its implementation. These modifications make the Pagano method feasible for multilayered FGM cylinders, and the computation in the implementation is independent of the total number of the layers, thus becoming less time-consuming than usual.