• Composites Research
• /
• v.26 no.1
• /
• pp.21-28
• /
• 2013

The ballistic limit of Carbon/Epoxy composite laminates with the finite effective area are predicted by using the quasi-static perforation test and semi-empirical formula. The perforation energy were calculated from force-displacement curve in quasi-static perforation test. Also, the actual ballistic limit and penetration energy were obtained through the high-velocity impact test. The quasi-static perforation test and high-velocity impact test were conducted for the specimens with 3 different effective areas. In the high-velocity impact test, the air gun impact tester were used, and the ballistic and residual velocity was measured. The required inputs for the semi-empirical formula were determined by the quasi-static perforation tests and high-velocity impact tests. The comparison between semi-empirical formula and high-velocity impact test results were conducted and examined. The ballistic limits predicted by semi-empirical formula were agreed well with high-velocity impact test results.

• Composites Research
• /
• v.32 no.1
• /
• pp.6-12
• /
• 2019

This paper describes the characteristics for mode I interlaminar and intralaminar fractures of cross-ply carbon/epoxy composite laminates. We obtained mode I interlaminar fracture toughness and mode I intralaminar fracture toughness based on energy release rate and Finite Element Analysis (FEA). For this purpose, the Double-Cantilever Beam (DCB) test and FEA were performed for cross-ply DCB specimens. Also, the behavior of load-displacement curve at the interlaminar and intralaminar crack was analyzed. The results show that mode I intralaminar fracture toughness was lower than mode I interlaminar fracture toughness in the cross-ply DCB specimen.

• Composites Research
• /
• v.34 no.2
• /
• pp.123-128
• /
• 2021

This paper dealt with multi-scale natural frequency characteristics of wavy CNT (carbon nanotube) reinforced composites by applying the Mori-Tanaka method, rule of mixture, and Halpin-Tsai equation. By compelling benefit of an ad-hoc Eshelby tensor, the load-transfer characteristics of CNT with a waviness implanted in the polymer matrix was determined. The numerical results obtained are in good agreement with those reported by other investigators. Furthermore, the new results reported in this paper show the interactions between CNT weight, waviness ratios and layup sequences of laminated composites. Key observation points are discussed and significant considerations are given in practical designing of CNT reinforced composites.

• 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.

• Journal of Korean Society of Steel Construction
• /
• v.13 no.1
• /
• pp.101-113
• /
• 2001

The main purpose of this paper is to present deflections of laminated composite plates on the two-parameter foundations. that is an elastic foundation with shear layer. This paper focuses on the deformation behaviour of anisotropic structures on elastic foundations. The third-order shear deformation theory is applied by using the double-fourier series. To validate the derived equations the obtained displacements for simply supported isotropic and orthotropic plates on elastic foundations are compared with those of Timoshenko and LUSAS program. The results show an excellent agreement for the isotropic and LUSAS program. The results show an excellent agreement for the isotropic and orthotropic plates on the elastic foundations. Numerical results for displacements are presented to show the effects of side-to-thickness ratio aspect ratio, material anisotropy and shear modulus of foundations.

• Aerospace Engineering and Technology
• /
• v.3 no.1
• /
• pp.257-266
• /
• 2004

A three node triangular element with drilling rotations incorporating improved higher-order zig-zag theory(HZZT) is developed to accurately assess the stress distribution through thickness of the laminated plate and analyze the vibration of pretwisted composite plates with embedded damping layer. Shear force matching conditions are enforced along the interfaces between the embedded damping patch and the border patch. The natural frequencies and model loss factors are calculated for cantilevered pretwisted composite blade with damping core with the present triangular element, and compared to experiments and MSC/NASTRAN using a layered combination of plate and solid elements.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2009.04a
• /
• pp.492-495
• /
• 2009

본 논문에서는 유한대판법(Finite Strip Method, FSM)을 이용하여 복합재료로 구성된 박판구조물의 좌굴해석을 수행하였다. 유한대판법에서의 변위장은 정현곡선으로 구성된 X방향 성분과 여현곡선의 Y방향 성분으로 구성되어 있는 면내성분, 면외성분으로 횡방향으로 3차 다항식과 보 진동함수를 사용하여 구성되었다. 각 적층판의 강성을 두께방향으로 적분하여 전체 강성을 구하고 최소 포텐셜 에너지 이론을 사용하여 구한 평형방정식에 대입하여 전체 강성행렬을 구하였다. 자유도의 감소로 인한 해석시간의 단축, 입력자료 작성 및 출력이 쉬운 점들이 유한대판법을 이용한 좌굴해석의 장점이다.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2001.05a
• /
• pp.65-68
• /
• 2001

In this research, damage initiation in singly oriented ply (SOP) FML under concentrated loading conditions was studied. The finite element method (FEM) base on the first order shear deformation theory is used for the analysis of fiber orientation effect on FML under concentrated loading conditions. The failure indices were calculated for the variation of fiber orientation and the results were compared with indentation experiments. The failure indices were well matched with damage initiation of SOP FML. Indentation results shows that the crack initiation of SOP FML is determined by stiffness induced by fiber orientation and tile penetration load of SOP FML are influenced by the deformation tendency and boundary conditions.

• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.331-336
• /
• 2004

This paper is concerned with numerical simulation of hypervelocity impacts(HVIs) of a projectile on laminated composite plate targets using SPH method. A one-parameter visco-plasticity model and damage model is used to describe the HVIs response of composite materials. The numerical simulation was carried out for a steel projectile striking to aluminum plate targets and for an aluminum projectile striking to laminated graphite/epoxy (Gr/Ep) composite plate targets. Through the numerical simulation, comparison with the HVIs response of isotropic materials and composite materials is discussed.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.8 no.2
• /
• pp.80-85
• /
• 1999

The purpose of this work is to investigate fatigue damage of quasi-isotropic laminates under tensile loading in different directions. Low cycle fatigue tests of [0/-60/+60]a laminates and [+30/-30/90]s lamina tes were carried out. Material systems used are AS4/Epoxy and AS4/PEEK. The fatigue damage of [+30/-30/90]s is very different from that of [0/-60/+60]s. The position of delamination generated at AS4/Epoxy and AS$/PEEK laminates were differentiated by the matrix difference that is, we suppose, the value of both GIcr(critical energy release rate of mode-I) and GIIIcr(critical energy release rate of mode-III) difference.