• Steel and Composite Structures
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• 제43권1호
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• pp.19-30
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• 2022

The static strength and fatigue crack resistance of the aircraft skin structures depend on the materials used and joint type. Most of the commercial aircraft's skin panel structures are made from aluminium alloy and carbon fibre reinforced epoxy. In this study, the fatigue resistance of four joint configurations (metal/metal, metal/composite, composite/composite and composite/metal) with riveted, adhesive bonded, and hybrid joining techniques are investigated with experiments and finite element analysis. The fatigue tests were tension-tension because of the typical nature of the loads on aircraft skin panels susceptible of experimenting fatigue. Experiment results suggest that the fatigue life of hybrid joints is superior to adhesive bonded joints, and these in turn much better than conventional riveted joints. Thanks to the fact that, for hybrid joints, the adhesive bond provides better load distribution and ensures load-carrying capacity in the event of premature adhesive failure while rivets induce compressive residual stresses in the joint. Results from FE tool ABAQUS analysis for adhesive bonded and hybrid joints agrees with the experiments. From the analysis, the energy release rate for adhesive bonded joints is higher than that of hybrid joints in both opening (mode I) and shear direction (mode II). Most joints show higher energy release rate in mode II. This indicates that the joints experience fatigue crack in the shear direction, which is responsible for crack opening.

• Steel and Composite Structures
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• 제19권6호
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• pp.1501-1510
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• 2015

The frequency selective surface (FSS) embedded hybrid composite materials have been developed to provide excellent mechanical and specific electromagnetic properties. Radar absorbing structures (RASs) are an example material that provides both radar absorbing properties and structural characteristics. The absorbing efficiency of an RAS can be improved using selected materials having special absorptive properties and structural characteristics and can be in the form of multi-layers or have a certain stacking sequence. However, residual stresses occur in FSS embedded composite structures after co-curing due to a mismatch between the coefficients of thermal expansion of the FSS and the composite material. In this study, to develop an RAS, the thermal residual stresses of FSS embedded composite structures were analyzed using finite element analysis, considering the effect of stacking sequence of composite laminates with square loop (SL) and double square loop (DSL) FSS patterns. The FSS radar absorbing efficiency was measured in the K-band frequency range of 21.6 GHz. Residual stress leads to a change in the deformation of the FSS pattern. Using these results, the effect of transmission characteristics with respect to the deformation on FSS pattern was analyzed using an FSS Simulator.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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• pp.63-66
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• 2000

This paper describes the need for a ductile Fiber Reinforced Plastic(FRP) reinforcement for concrete structures. Using the material hybrid and geometric hybrid, it is demonstrated that the pseudo-ductility characteristic can be generated in FRP rebar. Ductile hybrid FRP bars were successfully fabricated at 4mm and l0mm nominal diameters using an hand lay up method. Tensile specimens from these bars were tested and compared with behavior of FRP rebar and steel bar

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.34-37
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• 2001

This study developed Fiber/Particle Hybrid MMCs and analyzed their mechanical properties. Using $\textrm{Al}_2\textrm{O}_3f$ and $\textrm{Al}_2\textrm{O}_3p$ with the fiber to particle ratio of 1:1, 1:3, 1:5 hybrid preform and MMCs are fabricated. For the analysis of the mechanical properties, three point bending tests were preformed for the preform and tensile test for the MMCs. The experimental results show that the hybrid MMCs can be successfully fabricated using the equipment of fiber preform fabrication system and squeeze casting method. And as the amount of particle in hybrid MMCs increases, the tensile strength, elastic modulus and the volume fraction of reinforcement increases.

• Tribology and Lubricants
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• 제28권3호
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• pp.117-123
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• 2012

Tribological properties of hybrid type friction materials were studied. Hybrid friction materials were produced by combining non-steel(NS) and low-steel(LS) type friction materials. The emphasis of the investigation was given to possible synergistic effects from the two different friction materials, in terms of friction stability at high temperatures and the amplitude of friction oscillation, also known as stick-slip at low sliding speeds. The high temperature friction test results showed that the friction effectiveness of the hybrid friction material was well sustained compared to LS and NS friction materials. Wear resistance of the hybrid type was similar to LS friction materials. Examination of the rubbing surfaces after tests revealed that the friction characteristics of the hybrid friction material were attributed to the wear debris produced from low-steel friction materials, which were migrated to the surface of the non-steel friction material, forming new contact plateaus. The stick-slip amplitude and its frequency were pronounced when non-steel friction material was tested, while hybrid and low-steel types showed relatively small stick-slip amplitudes. These results suggest possible improvement of tribological properties by designing a hybrid composite of low-steel and non-steel friction materials.

• Structural Engineering and Mechanics
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• 제66권6호
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• pp.761-769
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• 2018

In this paper, we study the Carbon/Glass hybrid laminated composite plates, where the buckling behavior is examined using an accurate and simple refined higher order shear deformation theory. This theory takes account the shear effect, where shear deformation and shear stresses will be considered in determination of critical buckling load under different boundary conditions. The most interesting feature of this new kind of hybrid laminated composite plates is that the possibility of varying components percentages, which allows us for a variety of plates with different materials combinations in order to overcome the most difficult obstacles faced in traditional laminated composite plates like (cost and strength). Numerical results of the present study are compared with three-dimensional elasticity solutions and results of the first-order and the other higher-order theories issue from the literature. It can be concluded that the proposed theory is accurate and simple in solving the buckling behavior of hybrid laminated composite plates and allows to industrials the possibility to adjust the component of this new kind of plates in the most efficient way (reducing time and cost) according to their specific needs.

• Composites Research
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• 제18권6호
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• pp.1-8
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• 2005

섬유강화 복합재료는 우수한 기계적, 전자기적 물성 등으로 다양한 분야에서 응용되고 있다. 열경화성 복합재는 제작공정에서의 성형온도와 제품의 운용온도인 상온간의 온도차이로 형상의 변형(스프링 백)이 발생하게 된다. 이러한 스프링 백은 하이브리드 구조의 정밀한 형상 제작을 위해서 반드시 보정되어야할 부분이다. 본 연구에서는 유리섬유/에폭시 복합재와 카본섬유/에폭시 복합재로 구성된 비대칭 하이브리드 복합재를 경화사이클, 적층두께, 적층방법 등 다양한 조건을 적용하여 제작하고 3차원 좌표측정기를 이용하여 스프링 백을 측정하였다. 또한 고전 적층판 이론(CLT)과 유한요소해석(ANSYS)으로 스프링백을 예측하고 실험결과와 비교하였다. 고전 적층판 이론과 유한요소해석으로 예측된 스프링 백은 실험 결과와 잘 일치하였으며, 성형온도가 낮을수록 스프링 백이 감소되는 경향을 보임을 확인하였으나 근원적으로 스프링 백이 제거되지는 않았다.

• Advances in materials Research
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• 제4권2호
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• pp.97-111
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• 2015

Polypropylene short fiber (PP)-clay particulate-epoxy ternary composites were prepared by reinforcing PP short fiber and clay particles in the range of 0.1 phr to 0.7 phr into epoxy resin. Prepared hybrid composites were characterized for their mechanical, thermal and flame retardant properties. The obtained results indicated an increase in impact resistance, tensile strength, flexural strength and Young's modulus to an extent (up to 0.5 phr clay and 0.5 phr PP short fiber) and then decreases as the reinforcing phases are further increased. The thermal stability of these materials are found to increase up to 0.2 phr clay and 0.2 phr PP addition, beyond which it is decreased. Addition of clay is found to have the negative effect on epoxy-PP short fiber composites, which is evident from the comparison of mechanical and thermal properties of epoxy-0.5 phr PP short fiber composite and epoxy-0.5 phr PP short fiber-0.5 phr clay composite hybrid. UL-94 tests conducted on the composite hybrids have showed a reduction in the burning rate. Morphological observations indicated a greater fiber pull with the addition of clay. The performed tests in the present study indicated that materials under investigation have promising applications in construction, agriculture and decorative purposes.

• 한국안전학회지
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• 제34권3호
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• pp.1-7
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• 2019

A variety of composite materials are applied to industries for the realization of light weight and high strength. Fiber-reinforced composites have different strength and range of application depending on the weaving method. The mechanical performance of CFRP(Carbon Fiber Reinforced Plastic) in many areas has already been demonstrated. Recently, the application of hybridization has been increasing in order to give a compensation for brittleness of CFRP. Target materials are UHMWPE (Ultra High Molecular Weight Polyethylene), which has excellent cutting and chemical resistance, so it is applied not only to industrial safety products but also to places that lining performance is expected for household appliances. In this study, the CFRP and UHMWPE of plain weave, which are highly applicable to curved products, were molded into laminated hybrid composite materials by autoclave method. The mechanical properties and the mode I failure behavior between the layers were evaluated. The energy release rate G has decreased as the initial crack length ratio increased.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.486-490
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• 1997

Composite materials have varios complicated characteristics to the ply materials, ply orientations, ply stacking sequences and boundary conditions. Therefore, it is difficult to analysis composite materials. For efficient use of composite materials in engineering applications the dynamic behavior, that is, natural frequencies, nodal patterns should be informed. This study presents the experimental and FEM results for the free vibration of symmetrically and antisymmetrically laminated composite and hybrid composite rectangular plates. In order to demonstrate the validity of the experiment, FEM analysis using ANSYS was performed and natural frequencies experimentally obtined is compared with that calculated by FEM analysis. The results obtained from both experiment and FEM analysis show a good agreement.