• 대한기계학회논문집A
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• 제23권6호
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• pp.1048-1054
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• 1999

It is important to study the shielding effectiveness(SE) of reinforcing material of plastic composite materials against the electromagnetic(EM) waves. In this paper, SE of the shielding material of EM waves was investigated with actual experiments. The materials used in this study were made up of film, fiber and powder of conductive materials - Cu, Al, CF etc. Also, The resin film was used as matrix. The experiment was carried out by using a shielding evaluator(Shielding box) TR17302 with an ADVANTEST spectrum analyzer, model R3361C. It was found from the experimental results that copper, aluminum and carbon fiber were good candidates as a shielding material against the EM waves with increasing the SE as the composite was laminated. The characteristics of the SE against the EM waves depended on a mode of preparation of specimen. The effects of interval of wires on the SE were studied when the orientation and the space of Cu wires were changed. The SE strongly depended on the. orientation and the space of the Cu wire. SE decreased as the space of the Cu wires was increasing.

• Steel and Composite Structures
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• 제30권4호
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• pp.327-336
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• 2019

This paper presents geometrically nonlinear behavior of cracked fiber reinforced composite beams by using finite element method with and the first shear beam theory. Total Lagrangian approach is used in the nonlinear kinematic relations. The crack model is considered as the rotational spring which separate into two parts of beams. In the nonlinear solution, the Newton-Raphson is used with incremental displacement. The effects of fibre orientation angles, the volume fraction, the crack depth and locations of the cracks on the geometrically nonlinear deflections of fiber reinforced composite are examined and discussed in numerical results. Also, the difference between geometrically linear and nonlinear solutions for the cracked fiber reinforced composite beams.

• Advances in aircraft and spacecraft science
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• 제5권1호
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• pp.129-139
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• 2018

The composite materials are widely used in aircraft structures. Their relative rigidity/weight gives them an important advantage over the metal structures. The objective of this work is to analyze by the finite element method the mechanical behavior of composite plate type notched with various forms under tensile load. Two basic parameters were taken into consideration. The first, the form of the notch in order to see its effect on the stress and the failure load. The second, we studied the influence of the locale orientation of fiber around the plate's notch. These parameters are studied in order to see their effects on the distribution stress and failure load of the plate. The calculation of the failure load is determined numerically with the numerical code ABAQUS using the XFEM (extended Finite Element Modeling) based on the fracture mechanics. The result shows clearly that it is important to optimize the effect of fiber orientation around the notch.

• 한국생산제조학회지
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• 제19권2호
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• pp.235-240
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• 2010

The recent trend of vehicle design aims at crash safety and environmentally-friendly aspect. For the crash safety aspect, energy absorbing members should be absorbed with collision energy sufficiently. But vehicle structure must be light weight for the environmentally-friendly aspect, in order to improve fuel efficiency and to reduce tail gas emission. Therefore, the light weight of vehicle must be achieved in a status of securing safety of crash. An aluminum or CFRP (Carbon Fiber Reinforced Plastics) is representative one among the light-weight materials. In this study, impact collapse behavior of circular hybrid thin-walled member is evaluated. The hybrid members are manufactured by wrapping CFRP prepreg sheets outside the aluminum circular members in the autoclave. Because the CFRP is an anisotropic material whose mechanical properties change with its stacking condition, special attention is given to the effects of the stacking condition on the collapse behavior evaluation of the hybrid thin-walled member. Collapse mode and energy absorption capability of the hybrid thin-walled member are analyzed with change of the fiber orientation angle and interface number.

• 콘크리트학회논문집
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• 제21권5호
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• pp.541-548
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• 2009

지금까지 ECC의 인장거동 예측에 대한 이론적인 연구는 균열면에서 섬유가 균일하게 분산되어 있다고 가정하고 섬유 가교 곡선을 유도하는 방법으로 수행되었으며, 섬유의 기울어진 각도와 섬유사이의 간격은 섬유 가교 곡선을 예측하는데 큰 영향을 준다. 그러나 이론적으로 유도된 방법은 섬유의 기울어진 각도와 섬유 간격에 따라서 섬유가교 곡선의 형태가 달라지는 것을 모사하지 못하여 실제 섬유 가교 곡선과 차이를 보이며, ECC 인장거동을 예측할 때 큰 오차가 발생할 수 있다. 이 연구에서는 이러한 문제점을 해결하기 위하여 균열면에서 섬유 가교 작용에 기여하는 유효 섬유의 개수를 섬유의 기울어진 각도와 섬유 간격에 따라 고려한 후, 수정된 섬유 가교 곡선을 구하고, 이를 이용하여 보다 합리적인 ECC의 인장거동 예측기법을 제시하였다. 또한, 인장거동 예측에 중요한 변수인 초기 균열 강도, 섬유 가교 곡선에서의 최고 응력과 변위, 인장변형률, 균열간격을 구하기 위한 방법과 절차를 제시하였다. 그리고 예측 방법의 타당성을 평가하기 위하여 수정된 섬유 가교 곡선과 이론적인 섬유 가교 곡선으로 구한 ECC의 인장거동을 실험 결과와 비교하였다. 수정된 섬유 가교 곡선을 사용할 경우, 실험 결과와 잘 일치함을 알 수 있었으며, ECC의 인장거동을 합리적으로 예측할 수 있을 것으로 판단된다.

• 한국해양공학회지
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• 제11권3호
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• pp.69-75
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• 1997

A A12024-T3 plate has been reinforced with AFRP to be a Hybrid-Composite, APAL. The fatigue life of the APAL has been investigated. The effects of bonding surface, numbers of AFRP bonded and AFRP orientation on fatigue life have been compared with A12024-T3 plate. Fatigue life of APAL has been remarkedly increased compared with that of A12024-T3 plate. The fatigue life has depended on bonding surface and AFRP orientation, but no relationship could be found with numbers of AFRP laminates.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.184-187
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• 2002

Compression molding was specifically developed for replacement of metal components with composites. As the mechanical properties of the products are dependent on the separation and orientation, it is important to research the fiber mat structure and molding conditions. In this study, the effects of the fiber mat structure(NP: 5, 10, 25punches/$\textrm{cm}^2$) and the mold closure speed($\dot{\textrm{h}}$=0.1, 1, 10mm/min) on the viscosity of composites were discussed. The composites is treated as a Non-Newtonian power-law fluid. The parallel-plate plastometer is used and the viscosity is obtained from the relationship between the compression load and the thickness of the specimen.

• 한국해양공학회지
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• 제11권2호
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• pp.18-27
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• 1997

Al 6061 alloy reinforced with 10 vol.% ${\delta}-Al_2O_3$ short fiber was fabricated by Rheo-compocasting and squwwze cating. Extrusion processings were performed at temperatures from 40$0^{\circ}C$ to 55$0^{\circ}C$ with various extrusion ratio for curved shape dies. In proportion to the increase of extrusion ratios and temperatures, ultimate tensile strength for extruded materials improved. SEM observation of fractured surfsce was capcble oof accounting for fracture mechanism and bounding state of fiber and matrix.

• Steel and Composite Structures
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• 제27권5호
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• pp.567-576
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• 2018

The objective of this work is to analyze large deflections of a fiber reinforced composite cantilever beam under point loads. In the solution of the problem, finite element method is used in conjunction with two dimensional (2-D) continuum model. It is known that large deflection problems are geometrically nonlinear problems. The considered non-linear problem is solved considering the total Lagrangian approach with Newton-Raphson iteration method. In the numerical results, the effects of the volume fraction and orientation angles of the fibre on the large deflections of the composite beam are examined and discussed. Also, the difference between the geometrically linear and nonlinear analysis of fiber reinforced composite beam is investigated in detail.

• Structural Engineering and Mechanics
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• 제55권1호
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• pp.79-92
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• 2015

In this study, free vibration analyses of symmetric laminated cantilever and simply supported damaged composite beams are investigated by using finite element method (FEM). Free vibration responses of damaged beams are examined using Euler Bernoulli beam and classical lamination theories. A computer code is developed by using MATLAB software to determine the natural frequencies of a damaged beam. The local damage zone is assumed to be on the surface lamina of the beam by broken fibers after impact. The damaged zone is modeled as a unidirectional discontinuous lamina with $0^{\circ}$ orientations in this study. Fiber volume fraction ($v_f$), fiber aspect ratio ($L_f/d_f$), damage length ($L_D$) and its location (${\lambda}/L$), fiber orientation and stacking sequence parameters effects on natural frequencies are investigated. These parameters are affected the natural frequency values significantly.