• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.04a
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• pp.147-151
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• 1999

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.56-56
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• 2004

섬유강화 복합재료는 응용범위가 산업계 전반으로 빠르게 확대되고 있다. 개발 초기에는 하중을 감당하지 않는 이차 구조물에 주로 사용되어 왔으나, 점차 산업 전반의 I차 구조물(Primary Structure)에 쓰이는 등, 그 사용범위가 넓어지고 있으며, 취약한 두께방향 물성 향상의 필요성을 충족시키기 위해 다축경편(MWK) 복합재료에 대한 연구가 진행되고 있다. 본 논문에서는 다축경편(MWK) 복합재료의 기계적 체결부에 관한 응력해석을 연구하였다.(중략)

• Computational Structural Engineering
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• v.15 no.1
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• pp.17-30
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• 2002

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.6
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• pp.505-512
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• 2012

In this paper, an efficient yet accurate method for the thermal stress analysis using a first order shear deformation theory(FSDT) is presented. The main objective herein is to systematically modify transverse shear strain energy through the mixed variational theorem(MVT). In the mixed formulation, independent transverse shear stresses are taken from the efficient higher-order zigzag plate theory, and the in-plane displacements are assumed to be those of the FSDT. Moreover, a smooth parabolic distribution through the thickness is assumed in the transverse normal displacement field in order to consider a transverse normal deformation. The resulting strain energy expression is referred to as an enhanced first order shear deformation theory, which is obtained via the mixed variational theorem with transverse normal deformation effect(EFSDTM_TN). The EFSDTM_TN has the same computational advantage as the FSDT_TN(FSDT with transverse normal deformation effect) does, which allows us to improve the through-the-thickness distributions of displacements and stresses via the recovery procedure. The thermal stresses obtained by the present theory are compared with those of the FSDT_TN and three-dimensional elasticity.

• Journal of the KSME
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• v.22 no.1
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• pp.9-14
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• 1982

복합재료를 이용하여 부품제작을 한 후 어떠한 결합방법을 채택할 것인가를 결정할 때 고려해 야할 점을 기계적 결합법과 접착결합법을 비교하여 검토하였다. 기계적 결합은 하중을 많이 받고 분해 및 결합이 자주 예상되는 부품에 채택해야 할 것이며 복합재료의 특성을 고려하여 보강 시에 부착하는 평판의 섬유방향은 가급적 드릴구멍주위를 부드럽게 하여 응력집중을 낮출 수 있으며 하중의 종류에 따라 적층의 섬유방향을 조절함으로서 응력집중을 조절할 수 있다. 드릴 구멍 주위인 파손은 평판의 폭과 구멍의 직경등이 크게 작용함으로 강도해석을 할 경우에 응력 해석을 한 후 허용응력등을 결정해야할 것이다. 접착졀합법은 작업이 간단하나 신뢰도가 떨어지 므로 하중을 많이 받는 구조물에의 사용에 주의를 요하며 설계방법도 매우 다양하게 제안되어 있어 선택함에 있어 하중 환경조건등을 점검해야할 것이다. 접착결합법은 드릴구멍같은 불연속 성을 갖지 않기 때문에 응력집중이 생기지 않으나 접착층의 길이등 기하학적 형상에 따라 다르게 나타남으로 잡착층의 분리가 일어나지 않도록 설계되어야 한다. 특히 복합재료의 이방성인 성 질을 감안하여 접착층에 이웃하는 피접착층의 섬유방향에 주의해야 하며 층간응력이 파손에 미 치는 영향을 고려하여 설계에 임해야 한다.

• Composites Research
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• v.18 no.4
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• pp.44-51
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• 2005

In this paper, we developed the direct numerical simulation(DNS) model considering the geometry of yams which consist of 3D orthogonal woven composite materials, and using this model, the dynamic behavior of under transverse low-velocity impact has been studied. To build up the micromechanical model considering tow spacing and waviness, an accurate unit structure is presented and used in building structural plate model based on DNS. For comparison, DNS results are compared with those of the micromechanical approach which is based on the global equivalent material properties obtained by DNS static numerical tests. The effects with yarn geometrical irregularities which are difficult to consider in a macroscopic approach are also investigated by the DNS model. Finally, the multiscale model based on the DNS concepts is developed to enhance efficiency of analysis with real sized numerical specimen and macro/micro characteristics are presented.

• Journal of KSNVE
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• v.6 no.6
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• pp.781-790
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• 1996

The goal of current research is to suppress the acoustic noise radiated from vibration of composite plate structure. The induced noise can be reduced through the control of the corresponding structural vibration modes by using the piezoelectric materials as actuator. The acoustic fields are to be analyzed through the boundary element method (BEM) based on the Rayleigh intergral equation and structural system through the finite element method (FEM). The suppression of rediated sound is studied by adaping the piezoelectric material as the distributed actuator. Numerical results are presented on the sound radiation from composite plate of arbitrary boundary conditions, the noise reduction adapting the piezoelectric materials as distributed actuator. The results show the effectiveness and possibility of piezoelectric actuator in the control of sound radiation from composite structure.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.124-129
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• 1999

In this study, a design method for the flat sound radiator is developed to make new sound radiator system, whose shape is much thinner than that of conventional loudspeaker. Piezofilm (PVDF) is used as actuators of flat sound radiator. To avoid the distortion of sound radiated from flat sound radiator, the frequency response of radiated sound to be flat is taken as the design objective. The electrode pattern and orientation angle of piezofilm actuator is optimized to satisfy the design objective. The formulation is based on the coupled finite element and boundary element method. Genetic algorithm is used in the optimization process, which is useful in the optimization of discrete design variables. Frequency response with optimized piezofilm actuator is made flat enough to satify the design objective. For the enhancement of sound power, double-layered piezofilm actuators are also considered. The sound power with double-layered actuator becomes larger than that with single-layered actuator as expected.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.2
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• pp.23-28
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• 1998

In this paper, the experimental and numerical results of buckling loads for laminated composite plates are compared. Using boundary conditions of buckling test are all fixed supports. Experiments were conducted for plates with fiber angles $ heta$=30$^{\circ}$, 45$^{\circ}$,60$^{\circ}$ and aspect ratio a/b=0.8. Experimental results were obtained from load-deflection curves of buckling test. Numerical methods were presented to evaluate buckling loads, using structural analysis results from ANSYS.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.46-49
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• 2000

A decoupled thermo-~lezoelectric-mechanical model of composite laminates with surface bonded piezoelectric actuators, subjected to externally applied 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.