• Journal of Sensor Science and Technology
• /
• v.8 no.6
• /
• pp.440-447
• /
• 1999

Tensile stress loaded on smart composite structures and thermal stress occurred during the during process of the smart composite materials with embedded optical fiber sensors affect directly the mechanical behavior of the embedded optical fiber sensors within the smart composite structures. Stress distribution within the optical fiber sensors varies with respect to the stacking sequence of the composite laminate and the coating conditions of the optical fibers. The cracks occurred within the composite laminate affect not only the fracture of the composite laminate but also the fracture of the optical fiber sensors embedded within the composite laminate. In this study, firstly, stress distribution of the optical fiber sensors embedded within the composite laminate which is subjected to the tensile and thermal stresses was analyzed using Finite Element Method. And, secondly, the effect of the stacking sequence of the composite laminate and the coating conditions of the optical fiber sensors on the stress distribution of the optical fiber sensors was investigated. Finally, the effect of the crack occurred within the smart composite laminate on the fracture behavior of the optical fiber sensors was also observed through the tensile test.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.30 no.2
• /
• pp.59-66
• /
• 2002

In this paper, we present the simulataneous monitoring of the strain and temperature during cures f various composite laminates using fiber Bragg grating/extrinsic Fabry-Perot interferometric (FBG/EFPI) hybrid sensors. Three types of graphite/epoxy composite were used : a undirectional laminate, a symmetric cross-ply laminate, and a fabric laminate. Two FBG/EFPI hybrid sensors were embedded in each laminate at different directions and different locations. We performed the real time monitoring of fabrication strains and temperatures at two points within the composite laminates during cure process in an autoclave. Throuhg these experiments, FBG/EFPI sensors proved to be an efficient choice for smart cure monitoring of composite structures.

• Journal of Korean Society of Steel Construction
• /
• v.16 no.5 s.72
• /
• pp.621-628
• /
• 2004

This paper introduces a new theory, that in a stiffened plate, a steel stiffener could be substituted a composite material in order to prevent from buckling. Changing a steel stiffener into a composite material would not only preclude welding, but could also prevent damage to the material due to fatigue and corrosion.A composite material is assumed to adhere to a steel plate, and is never separated from the plate until the steel plate reaches buckling.Such plate has variable shapes, with different lengths and widths, and also shows an anisotropic material property. LUSAS, a commercial finite element analysis package, was used in the buckling analysis.This paper investigated buckling behavior in anisotropic composite plates with variable parameters.

• Composites Research
• /
• v.33 no.6
• /
• pp.377-382
• /
• 2020

The free vibration characteristics of corrugated laminated composite plates with axial stiffeners is investigated using the Rayleigh-Ritz method. The plate is stiffened by beams with open cross-section area. The equivalent homogenization model is used for the corrugated laminated composite plates. This homogenization model is treated a corrugated plate as an orthotropic plate that has different material properties in two perpendicular directions. The motion of equivalent plate is represented on the basis of the first order shear deformation theory (FSDT) to account for the effect of rotary inertia and transverse shear deformation. Stiffeners are considered as discrete elements to predict the local vibration mode to be generated by the presence of stiffeners. To validate the proposed analytical approach, natural frequencies and vibration mode shapes from the analytical method are compared with those from the FEA by ANSYS.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.13 no.1
• /
• pp.129-138
• /
• 2000

Composites are finding increasing use in a wide variety of engineering applications due to their outstanding mechanical properties. A number of studies have focused on the development of new materials as well as the response of composite structures to static and dynamic loads by assuming the external driving forces to be deterministic. However, there ate many situations in practice where the exciting forces vary randomly. In this work, the nonlinear response of laminated composite plates excited by stochastic loading is studied by the finite element method. Classical, first-order and third-order shear theories for plates are used in the finite element formulation. Since most composites exhibit significant nonlinearity in the shear stress-strain law, this is included in the present analysis.

• Composites Research
• /
• v.29 no.5
• /
• pp.243-248
• /
• 2016

Although thermoset carbon fiber composite bipolar plates not only have high mechanical properties but also high corrosion resistance in acid environment, high manufacturing cost and low bulk electrical conductivity are the biggest obstacle to overcome. In this research, thermoplastic polymer is employed for the matrix of carbon composite bipolar plate to increase both the manufacturing productivity and bulk electric conductivity of the bipolar plate. In order to increase the electrical conductivity and strength, plain type carbon fabric rather than chopped or unidirectional fibers is used. Also nano particles are embedded in the thermoplastic matrix to increase the bulk resistance of the bipolar plate. The area specific resistance and the mechanical strength of the developed bipolar plate are measured with respect to the environmental temperature and stack compaction pressure.

• Composites Research
• /
• v.16 no.5
• /
• pp.39-44
• /
• 2003

Embedding viscoelastic-damping materials into composites can greatly increase the damping properties of composite structures. Usually viscoelastic-damping materials behave isotropically so that their damping properties are the same in all directions. In these days, there is a desire to develop viscoelastic-damping materials that behave orthotropically so that damping properties vary with material orientation. These orthotropic damping materials can be made by embedding rows of thin wires within the viscoelastic materials. These wires add significant directional stiffness to the damping materials. where the stiffness variation with wire orientation follows classical lamination theory. In this paper, the loss factor of composite laminate was evaluated based on Ni and Adams' theory. To investigate the effect of directional damping material, the low-velociy impact response analysis was also performed. The present analysis results show that directional damping material has a great influence on vibration and damping characteristic of composite laminate.

• Composites Research
• /
• v.26 no.5
• /
• pp.328-333
• /
• 2013

In this study, bone plate made of glass/polypropylene composite material which was applied to an artificial bone was tested to check the service ability under fatigue loading. To check serviceability of composite bone plates fatigue test was carried out considering changes in the moisture absorption rate, locking position of screws and loading condition. Test results showed that all the tested specimens had the fatigue life more than one million cycles which was much higher fatigue life than the expected value of 650,000 cycles. Screw position was not critical impact on the deformation of the fracture site. In this paper, the mechanical performance of the glass/polypropylene composite was verified by fatigue test under various water absorption conditions, and this result may give useful information on the design of composite bone plate.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 1999.11a
• /
• pp.22-27
• /
• 1999

고급복합재료(advanced composite material)는 여러 가지 훌륭한 장점에도 불구하고 건설기술자에게는 그 이론이 너무 복잡하여 건설구조에 대한 응용이 지연되고 있다. [$\alpha/\beta/\beta/\gamma/\alpha/\alpha/\beta$]r, $\alpha$=-$\beta$, $\gamma$=0$^{\circ}$ 또는 90$^{\circ}$ 와 같은 몇 가지 배향각을 갖은 적층판은, r이 증가함에 따라, $B_{i,j}$강성이 0으로 접근한다(1995). 건설구조물은 그 치수가 커서 r이 증가해도 지간 대 두께비가 충분히 커서, 횡방향 변형율(${\varepsilon}_{xz}$,${\varepsilon}_{yz}$)의 영향이 무시될 수 있다. 이 경우 판의 지배방정식은 간단한 특별직교이방성판의 식으로 변화된다. 김덕현은 토목구조물에 흔히 적용될 수 있는 이러한 배향각을 가진 적층판의 지배방정식을 취급이 간단한 특별직교 이방성 판의 경우로 변경시킨 다음 해석을 더 간단히 진행할 수 있도록 기술자들이 유사 등방성 상수(quasi-isotropic constant)를 사용하여 낮익은 등방성판의 방정식을 사용하여 답을 구한 다음 그가 개발한 "수정계수(correction factor)"를 사용하여 "정확한"해를 구하는 방법을 발표한바 있다(1991).는 방법을 발표한바 있다(1991).

• Composites Research
• /
• v.15 no.4
• /
• pp.1-8
• /
• 2002

In this study, the rigidities of fiber-reinforced composite corrugated plates are derived to achieve the weight reduction, high strength, and high stiffness. The vibration of the corrugated plates for all the conventional boundary conditions in the plates is analyzed numerically by applying the derived rigidities, and so the analysis system is programmed to obtain the results by using Visual Basic language. Consequently, the characteristics of fiber-reinforced composite corrugated plates can be easily investigated from the results provided by the programmed system.