• Title/Summary/Keyword: Composite Laminates

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Experimental and numerical analysis of composite beams strengthened by CFRP laminates in hogging moment region

  • El-Shihy, A.M.;Fawzy, H.M.;Mustafa, S.A.;El-Zohairy, A.A.
    • Steel and Composite Structures
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    • v.10 no.3
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    • pp.281-295
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    • 2010
  • An experimental and a non linear finite element investigation on the behavior of steel-concrete composite beams stiffened in hogging moment region with Carbon Fiber Reinforced Plastics (CFRP) sheets is presented in this paper. A total of five specimens were tested under two-point loads. Three of the composite beams included concrete slab while the other two beams had composite slabs. The stiffening was achieved by attaching CFRP sheets to the concrete surface at the position of negative bending moment. The suggested CFRP sheets arrangement enhanced the overall beam behavior and increased the composite beam capacity. Valuable parametric study was conducted using a three dimensional finite element model using ANSYS program. Both geometrical and material nonlinearity were included. The studied parameters included CFRP sheet arrangement, concrete strength and degree of shear connection.

Strengthening of steel-concrete composite beams with prestressed CFRP plates using an innovative anchorage system

  • Wan, Shi-cheng;Huang, Qiao;Guan, Jian
    • Steel and Composite Structures
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    • v.32 no.1
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    • pp.21-35
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    • 2019
  • This study investigates the flexural behavior of steel-concrete composite beams strengthened with prestressed carbon fiber-reinforced polymer (CFRP) plates. An innovative mechanical anchorage system was developed. The components of the system can be easily assembled on site before applying a prestressing force, and removed from the structures after strengthening is completed. A total of seven steel-concrete composite specimens including four simply supported beams strengthened at the positive moment region and three continuous beams strengthened at the negative moment region were tested statically until failure. Experimental results showed that the use of prestressed CFRP plates enhanced the flexural capacity and reduced the mid-span deflection of the beams. Furthermore, by prestressing the CFRP laminates, the material was used more efficiently, and the crack resistance of the continuous composite specimens at the central support was significantly improved after strengthening. Overall, the anchorage system proved to be practical and feasible for the strengthening of steel-concrete composite beams. The theoretical analysis of ultimate bearing capacity is reported, and good agreement between analytical values and experimental results is achieved.

Impact Resistance of Composite Laminates Manufactured by New z-Pinning Technique (새로운 z-피닝 기술로 제작된 복합적층판의 내충격 특성)

  • Choi, Ik-Hyeon;Ahn, Seok-Min;Yeom, Chan-Hong;Hwang, In-Hee;Lee, Dae-Sung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.37 no.7
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    • pp.693-700
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    • 2009
  • In this paper, conventional z-pinning technology which can be used to reinforce inter-laminar property of laminated composites is introduced and new z-pinning technique recently proposed by author is also introduced. On some trial specimens manufactured by the new z-pinning technique, the low-velocity impact test was performed and impact damage area was measured. Similar impact test was performed on normal composite laminate specimens and those test results were compared to each other. Consequently, it can be seen that the new z-pinning technique is more useful in applying to mass production of z-pinned composite laminate structures than the conventional techniques and some clear improvement on impact resistance of z-pinned composite laminates manufactured by the new z-pinning technique is observed.

Strength Prediction on Composite Laminates Including Material Nonlinearity and Continuum Damage Mechanics (재료 비선형과 연속체 손상역학을 고려한 복합 적층판의 강도 예측)

  • Park, Kook-Jin;Kang, Hee-Jin;Shin, Sangjoon;Choi, Ik-Hyun;Kim, Minki;Kim, Seung-Jo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.42 no.11
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    • pp.927-936
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    • 2014
  • This paper presents development and verification of the progressive failure analysis upon the composite laminates. Strength and stiffness of the fiber-reinforced composite are analyzed by property degradation approach with emphasis on the material nonlinearity and continuum damage mechanics (CDM). Longitudinal and transverse tensile modes derived from Hashin's failure criterion are used to predict the thresholds for damage initiation and growth. The modified Newton-Raphson iterative procedure is implemented for determining nonlinear elastic and viscoelastic constitutive relations. Laminar properties of the composite are obtained by experiments. Prediction on the un-notched tensile (UNT) specimen is performed under the laminate level. Stress-strain curves and strength results are compared with the experimental measurement. It is concluded that the present nonlinear CDM approach is capable of predicting the strength and stiffness more accurately than the corresponding linear CDM one does.

Fatigue Damage Evaluation of Woven Carbon-Fiber-Reinforced Composite Materials by Using Fatigue Damage Model (피로 손상 모델을 이용한 직조 탄소섬유강화 복합재료의 피로 손상 평가)

  • Park, Hong-Sun;Choi, Jung-Hun;Koo, Jae-Mean;Seok, Chang-Sung
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.6
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    • pp.757-762
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    • 2010
  • Owing to the high specific strength and stiffness of composite materials, they are extensively used in mechanical systems and in vehicle industries. However, most mechanical structures experience repeated load and fatigue. Therefore, it is important to perform fatigue analysis of fiber-reinforced composites. The properties of composite laminates vary depending upon the stacking sequence and stacking direction. Fatigue damage of composite laminates occurs according to the following sequence: matrix cracking, delamination, and fiber breakage. In this study, fatigue tests were performed for damage analysis. Fatigue damages, which have to be considered in fatigue analysis, are determined by using the stiffness values calculated from hysteresis loops, and the obtained fatigue damage curve is examined using Mao's equation and Abdelal's equation.

Thermal Residual Stresses and Spring back Effects on the Frequency Selective Surface Embedded Composite Laminates (주파수 선택막이 삽입된 복합재 평판의 잔류 열응력과 스프링 백 효과)

  • Park, Kyoung-Mi;Seo, Yun-Seok;Chun, Heoung-Jae;Hong, Ic-Pyo;Park, Yong-Bae;Kim, Yun-Jae
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.26 no.6
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    • pp.475-481
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    • 2013
  • The residual stresses occur in the Frequency Selective Surface(FSS) embedded hybrid composite structures after co-curing due to mismatch among the coefficient of thermal expansions and stiffness values between the FSS and composite materials. The spring backs occur due to these residual stresses. Therefore, in this paper, the spring-backs caused by residual stresses in FSS embedded composite structures were studied with considering effect of symmetric and unsymmetric stacking sequence of composite laminates.

A comparative study for beams on elastic foundation models to analysis of mode-I delamination in DCB specimens

  • Shokrieh, Mahmood Mehrdad;Heidari-Rarani, Mohammad
    • Structural Engineering and Mechanics
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    • v.37 no.2
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    • pp.149-162
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    • 2011
  • The aim of this research is a comprehensive review and evaluation of beam theories resting on elastic foundations that used to model mode-I delamination in multidirectional laminated composite by DCB specimen. A compliance based approach is used to calculate critical strain energy release rate (SERR). Two well-known beam theories, i.e. Euler-Bernoulli (EB) and Timoshenko beams (TB), on Winkler and Pasternak elastic foundations (WEF and PEF) are considered. In each case, a closed-form solution is presented for compliance versus crack length, effective material properties and geometrical dimensions. Effective flexural modulus ($E_{fx}$) and out-of-plane extensional stiffness ($E_z$) are used in all models instead of transversely isotropic assumption in composite laminates. Eventually, the analytical solutions are compared with experimental results available in the literature for unidirectional ($[0^{\circ}]_6$) and antisymmetric angle-ply ($[{\pm}30^{\circ}]_5$, and $[{\pm}45^{\circ}]_5$) lay-ups. TB on WEF is a simple model that predicts more accurate results for compliance and SERR in unidirectional laminates in comparison to other models. TB on PEF, in accordance with Williams (1989) assumptions, is too stiff for unidirectional DCB specimens, whereas in angle-ply DCB specimens it gives more reliable results. That it shows the effects of transverse shear deformation and root rotation on SERR value in composite DCB specimens.

Thermal post-buckling analysis of a laminated composite beam

  • Akbas, Seref D.
    • Structural Engineering and Mechanics
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    • v.67 no.4
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    • pp.337-346
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    • 2018
  • The purpose of this study is to investigate thermal post-buckling analysis of a laminated composite beam subjected under uniform temperature rising with temperature dependent physical properties. The beam is pinned at both ends and immovable ends. Under temperature rising, thermal buckling and post-buckling phenomena occurs with immovable ends of the beam. In the nonlinear kinematic model of the post-buckling problem, total Lagrangian approach is used in conjunction with the Timoshenko beam theory. Also, material properties of the laminated composite beam are temperature dependent: that is the coefficients of the governing equations are not constant. In the solution of the nonlinear problem, incremental displacement-based finite element method is used with Newton-Raphson iteration method. The effects of the fibber orientation angles, the stacking sequence of laminates and temperature rising on the post-buckling deflections, configurations and critical buckling temperatures of the composite laminated beam are illustrated and discussed in the numerical results. Also, the differences between temperature dependent and independent physical properties are investigated for post-buckling responses of laminated composite beams.

Realtime Detection of Damage in Composite Structures by Using PVDE Sensor (압전고분자 센서를 이용한 복합재 구조의 실시간 손상탐지)

  • ;Y. A. Dzenis
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2002.10a
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    • pp.118-121
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    • 2002
  • Polyvinylidene di-fluoride (PVDF) film sensor appeared to be practically useful for the structural health monitoring of composite materials and structures. PVDF film sensors were either attached to or embedded in the graphite/epoxy composite (CFRP) samples to detect the fatigue damage at the bondline of single-lap joints or the tensile failure of unidirectional laminates. PVDF sensors were sensitive enough to detect and determine the crack front in linear location since composites usually produce very energetic acoustic emission (AE). PVDF sensors are extremely cost-effective, as flexible as other plastic films, in low profile as thin as a few tens of microns, and have relatively wide-band response, all of which characteristics are readily utilized for the structural health monitoring of composite structures. Signals due to fatigue damage showed a characteristics of mode II (shear) type failure whereas those from fiber breakage at DEN notches showed that of mode I (tensile) type fracture.

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Development of Composite Pedestrian Bridge Deck and Its Snap-fit Connection (착탈결구식 복합소재 바닥판의 연결부 거동분석)

  • Lee, Sung-Woo;Jeong, Gyu-Sang
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2005.11a
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    • pp.280-284
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    • 2005
  • Existing construction materials such as concrete and steel have chronic problems; deterioration and corrosion. Owing to its special features of light weight ‘ high durability, anti-corrosion, composite material used in civil infrastructure can not only solve fundamental problems of deterioration and corrosion, but also reduce both construction and maintenance cost significantly. After the fabrication of deck panel with snap-fit connection by pultrusion through composite design according to stacking sequence of composite laminates and structural analysis, performance of decks will be verified and evaluated by structural tests.

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