Mechanical behaviour between adjacent cracks in CFRP plate reinforced RC slabs

Xin Yuan,Hongyu Bai,Chen Sun,Qinqing Li,Yanfeng Song 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.3

This paper discussed and analyzed the interfacial stress distribution characteristic of adjacent cracks in Carbon Fiber Reinforced Polymer (CFRP) plate strengthened concrete slabs. One un-strengthened concrete test beam and four CFRP platestrengthened concrete test beams were designed to carry out four-point flexural tests. The test data shows that the interfacial shear stress between the interface of CFRP plate and concrete can effectively reduce the crack shrinkage of the tensile concrete and reduces the width of crack. The maximum main crack flexural height in pure bending section of the strengthened specimen is smaller than that of the un-strengthened specimen, the CFRP plate improves the rigidity of specimens without brittle failure. The average ultimate bearing capacity of the CFRP-strengthened specimens was increased by 64.3% compared to that without CFRP-strengthen. This indicites that CFRP enhancement measures can effectively improve the ultimate bearing capacity and delay the occurrence of debonding damage. Based on the derivation of mechanical analysis model, the calculation formula of interfacial shear stress between adjacent cracks is proposed. The distributions characteristics of interfacial shear stress between certain crack widths were given. In the intermediate cracking region of pure bending sections, the length of the interfacial softening near the mid-span cracking position gradually increases as the load increases. The CFRP-concrete interface debonding capacity with the larger adjacent crack spacing is lower than that with the smaller adjacent crack spacing. The theoretical calculation results of interfacial bonding shear stress between adjacent cracks have good agreement with the experimental results. The interfacial debonding failure between adjacent cracks in the intermediate cracking region was mainly caused by the root of the main crack. The larger the spacing between adjacent cracks exists, the easier the interfacial debonding failure occurs.

Interfacial Crack Propagation Under Various Mode-Mixes

Park, Byung-Sun,Chai, Young-Suck The Korean Society of Mechanical Engineers 2002 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.16 No.1

Initiation and propagation of interfacial crack along bimaterial interface are considered in this study. A biaxial loading device for a single specimen is used for obtaining a wide range of mode-mixities. The specimen is an edge-cracked bimaterial strip of glass and epoxy; the biaxial loading device, being capable of controlling displacements in two perpendicular directions, is developed. A series of interfacial crack initiation and Propagation experiments are conducted using the biaxial loading device for various mixed modes. Normal crack opening displacement (NCOD) is measured near crack front by a crack opening interferometry and used for extracting fracture parameters. From mixed mode interfacial crack initiation experiments, large increase in toughness with shear components is observed. The behavior of interfacial crack propagation analyzed as a function of mode-mix shows that initial crack propagation is delayed with increase of mode-mixity, and its velocity is increased with positive mode-mixity but decreased with negative case. However, it is found that crack propagation is less accelerated with positive mode-mixity than the negative mode-mixity, which may be caused by contact and/or effects of friction between far field and near-tip Held along the interfacial crack.

계면균열의 인성과 진전 거동

尹命辰,崔柄善 慶一大學校 2002 論文集 Vol.18 No.-

Interfacial crack problems between fiber and matrix in composite materials were discussed. A series of interfacial crack initiation and propagation experiments were conducted using the biaxial loading device for various mode-mixes. From the series of crack experiments, it could be seen that there was a large increase in toughness with shear components. The behavior of interfacial crack propagation is also analyzed as a function of mode-mix. The result shows that the initial crack propagation was delayed as an increase of absolute value of mode-mix. It could be seen that crack initiation velocity was increased with positive mode-mix and was decreased with negative mode-mix. However, it was found that crack propagation was less accelerated with positive mode-mix than the negative mode-mix. Possible causes of trend were thought be the different behavior of contact and/or effects of friction between far field and near-tip field along the interfacial crack.

Viscoelastic Analysis of an Interface Edge Crack in a Bonded Polymeric Film

Lee, Sang-Soon The Korean Society Of SemiconductorDisplay Technol 2010 반도체디스플레이기술학회지 Vol.9 No.3

Interfacial stress singularity induced in an analysis model consisting of the polymeric thin film and the elastic substrate has been investigated using the boundary element method. The interfacial singular stresses between the viscoelastic thin film and the elastic substrate subjected to a uniform moisture ingression are investigated for the case of a small interfacial edge crack. It is assumed that moisture effects are assumed to be analogous to thermal effects. Then, the overall stress intensity factor for the case of a small interfacial edge crack is computed. The numerical procedure does not permit calculation of the limiting case for which the edge crack length vanishes.

탄소섬유쉬트로 보강된 철근콘크리트보의 계면박리에 대한 해석적 연구

심종성,배인환,Sim, Jong-Sung,Bae, In-Hwan 한국콘크리트학회 1999 콘크리트학회지 Vol.11 No.2

본 연구의 목적은 탄소섬유쉬트로 보강된 시험체의 주요 파괴모드인 계면모드인 계면박리 모드에 의한 부재의 파괴를 규명하는 것이다. 탄소섬유쉬트로 보강된 손상된 보시험체의 계면박리 모드를 해석하기 위하여 선형탄성 파괴역학(LEFM)의 컴플라이언스법과 유한요소법을 사용하여 계면파괴 역학변수인 에너지해방율(strain energy release rate, G)을 고찰하였다. 손상된 단순 보시험체의 해석결과, 최대 에너지해방율($G_{max}$)은 에폭시 접착두께에 관계없이 바깥 휨균열에서 시작된 계면 전단 균열 길이가 18mm 부근에서 발생하였다. 보강보의 강도 해석결과, 극한강도 설계법에 따른 단면의 공칭 휨 강도에 대한 계면박리에 의해 부재가 파괴되는 것으로 해석되었다. 또한 적용된 접착두께 1mm~3mm는 에너지해방율에 거의 영향을 미치지 않아 계면박리의 주요 인자가 아닌 것으로 나타났다. The purpose of this study is to analyze the interface debonding of RC beams strengthened by carbon fiber sheet(CFS). The behavior of damaged RC beams strengthened with CFS is analytically investigated next using linear elastic fracture mechanics(LEFM) approach and the finite element method. The study includes an investigation of the separation mode by interface fracture of the strengthening materials due to the interfacial shear and normal stresses. The numerical method is presented to obtain the value of interfacial fracture parameter such as the strain energy release rate. Based on the results of this study, it is found that the critical case occurs when the interfacial cracks occur within a short region of the flexural crack. The CFS strengthening has not an adequate factor of safety against interfacial debonding of CFS. Furthermore, for the thicknesses of the adhesive studied[1mm~3mm], it is no noticeable effect on the strain energy release rate.

Viscoelastic Analysis of an Interface Edge Crack in a Bonded Polymeric Film

이상순 한국반도체디스플레이기술학회 2010 반도체디스플레이기술학회지 Vol.9 No.3

Interfacial stress singularity induced in an analysis model consisting of the polymeric thin film and the elastic substrate has been investigated using the boundary element method. The interfacial singular stresses between the viscoelastic thin film and the elastic substrate subjected to a uniform moisture ingression are investigated for the case of a small interfacial edge crack. It is assumed that moisture effects are assumed to be analogous to thermal effects. Then, the overall stress intensity factor for the case of a small interfacial edge crack is computed. The numerical procedure does not permit calculation of the limiting case for which the edge crack length vanishes.

J-T에 대한 3차원 반타원 계면균열선단 응력장의 기술

이형일(Hyungyil Lee),최호승(Ho-Seung Choi) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.8

Many research works have validated the J-T approach to elastic-plastic crack-tip stress fields in a variety of plane strain specimens. To generalize the validity of J-T method, further investigations are however needed for more practical 3D structures than the idealized plane strain specimens. In this work, we perform 3D finite element (FE) modeling of welded plate and straight pipe, and accompanying elastic, elastic-plastic FE analyses. Manual 3D modeling is almost prohibitive, since the models contain semi-elliptical interfacial cracks which require singular elements. To overcome this kind of barrier, we develop a program generating the meshes for semi-elliptical interfacial cracks. We then compare the detailed 3D FE stress fields to those predicted with J-T two parameters. Thereby we extend the validity of J-T application to 3D structures and infer some useful informations for the design or assessment of pipe welds.

항복강도 불일치 반타원 계면균열 선단에서의 응력장

최호승(Ho-Seung Choi),이형일(Hyungyil Lee) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.8

Many research works have validated the J-T approach for elastic-plastic crack-tip stress fields in a variety of plane strain specimens. To generalize the validity of J-T method, further investigations are however needed for more practical 3D structures than the idealized plane strain specimens. In this work, we perform 3D finite element (FE) modeling of welded plate and straight pipe, and accompanying elastic, elastic-plastic FE analyses. Manual 3D modeling is almost prohibitive, since the models contain semi-elliptical interfacial cracks which require singular elements. To overcome this kind of barrier, we develop a program generating the meshes for semi-elliptical interfacial cracks. We then compare the detailed 3D FE stress fields to those predicted with J-T two parameters. Thereby we extend the validity of J-T application to 3D strength-mismatched welded joints, and infer some useful informations for the design or assessment of pipe welds.

비선형 경사 균열면에서의 고조파 발생 특성 해석

김노유(Nohyu Kim),양승용(Seungyong Yang) 한국비파괴검사학회 2012 한국비파괴검사학회지 Vol.32 No.4

비선형 스프링 모델과 섭동법을 기초로 비선형 균열면에 경사 입사된 초음파에 의해 발생되는 2차 고조파 초음파의 크기를 계산하였다. 비선형 균열계면에서 만들어지는 반사파와 굴절파의 기본주파수 성분과 2차 고조파 성분의 크기를 입사각과 균열계면의 계면강성을 변화키면서 조사하였다. 계면강성에 관계없이 균열계면이 초음파 진행 방향과 비슷한 경우 반사와 굴절파 모두에서 2차 고조파의 발생은 거의 없었지만, 그렇지 않은 경우에는 계면 입사각은 물론 계면 강성에 따라 2차 고조파의 크기는 크게 변화하였다. 투과파는 물론 반사파에서도 2차 고조파 성분이 유의성 있게 발생됨을 수치 해석을 통해 확인하였다. Based on the nonlinear spring model coupled with perturbation method, 2nd harmonic waves generated by oblique incident ultrasound on nonlinear crack interface were calculated and investigated. Reflected and transmitted waves from the interface were determined and analyzed at various angle of incidence for the cracks with different interfacial stiffness in order to estimate the 2nd harmonic generation of incident ultrasound. It was shown in computer simulation that the 2nd harmonic components changed much with the increase of incidence angle in both reflected and transmitted wave, but became very small when the incident angle approached toward 90 degree. It can be concluded that the 2nd harmonic component of reflected wave has a meaningful amplitude as much as the transmitted 2nd harmonic wave from partly closed crack.

정적 광탄성 실험 Hybrid 법에 의한 에너지 해방률에 관한 연구

신동철(Dong-Chul Shin),황재석(Jai-Sug Hawong),남성수(Sung-Su Nam) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.8

In this research, dynamic energy release rate of a propagating interfacial crack in the bimaterial is developed. If the interfacial crack propagating velocity(c) is equal to zero(=0), the definition for the dynamic energy release rate of a propagating interfacial crack in the bimaterial reduce to one's of static energy release rate of interfacial crack in the bimaterial. Using above conception for static energy release rate and static photoelastic experiment hybrid method, we have studied the variations of static energy release rate according to the geometric conditons of interfacial crack in the bimaterial.