• 대한기계학회논문집A
• /
• 제29권10호
• /
• pp.1329-1335
• /
• 2005

An aluminum or CFRP (Carbon Fiber ReinfDrced Plastics)is representative one of light-weight materials but its axial collapse mechanism is different from each other. The aluminum member absorbs energy by stable plastic deformation, while the CFRP member absorbs energy by unstable brittle failure with higher specific strength and stiffness than those in the aluminum member. In an attempt to achieve a synergy effect by combining the two members, aluminum CFRP compound square members were manufactured, which are composed of aluminum members wrapped with CFRP outside aluminum square members with different fiber orientation angle and thickness of CFRP, and axial collapse tests were performed fur the members. The axial collapse characteristics of the compound members were analyzed and compared with those of the respective aluminum members and CFRP members. Test results showed that the collapse of the aluminum CFRP compound member complemented unstable brittle failure of the CFRP member due to ductile characteristics of the inner aluminum member. The collapse modes were categorized into four modes under the iuluence of the fiber orientation angle and thickness of CFRP. The absorbed energy Per unit mass, which is in the light-weight aspect was higher in the aluminum CFRP compound member than that in the aluminum member and the CFRP member alone.

• Steel and Composite Structures
• /
• 제47권4호
• /
• pp.455-466
• /
• 2023

To investigate the load bearing capacity of axially preloaded circular hollow section (CHS) stub columns strengthened by carbon fiber reinforced polymer (CFRP), theoretical analysis is carried out. The yield strength and the ultimate strength of a CFRP strengthened preloaded CHS stub column are determined at the yielding of the CHS tube and at the CFRP fracture, respectively. Theoretical models are proposed and corresponding equations for calculating the static strengths, including the yield strength and the ultimate strength, are presented. Through comparison with reported experimental results, the theoretical predictions on the static strengths are proved to be accurate. Through finite element (FE) analyses, parametric studies for 258 models of CFRP strengthened preloaded CHS stub columns are conducted by considering different values of tube diameter, tube thickness, CFRP layer and preloading level. The static strengths of the 258 models predicted from presented equations are proved to be in good agreement with FE simulations when the diameter-to-thickness ratio is less than 90ε². The parametric study indicates that the diameter and the thickness of the steel tube have great effects on CFRP strengthening efficiency, and the recommended ranges of the diameter and the thickness are proposed.

• 한국자동차공학회논문집
• /
• 제13권5호
• /
• pp.50-56
• /
• 2005

Aluminum member absorbs energy by stable plastic deformation under axial loading. While CFRP(Carbon Fiber Reinforced Plastics) member absorbs energy by unstable brittle failure but its specific strength and stiffness is higher than those of aluminum member. In this study, for complement of detects and synergy effect by combination with the advantages of each member, the axial collapse tests were performed for aluminum CFRP members which are composed of aluminum members wrapped with CFRP outside aluminum circular members. Based on the respective collapse characteristics of aluminum and CFRP members, crushing behavior and energy absorption characteristics were analyzed for aluminum CRRP members which have different CFRP fiber orientation angle and thickness Test results showed that aluminum CFRP members supplemented the unstable brittle failure of CFRP members due to ductile nature of inner aluminum members. It turned out that the CFRP fiber orientation angle and thickness influence energy absorption capability together with the collapse mode of the members.

• Steel and Composite Structures
• /
• 제33권5호
• /
• pp.629-640
• /
• 2019

This paper presents a theoretical and finite element (FE) study on the stress intensity factors of double-edged cracked steel beams strengthened with carbon fiber reinforced polymer (CFRP) plates. By simplifying the tension flange of the steel beam using a steel plate in tension, the solutions obtained for the stress intensity factors of the double-edged cracked steel plate strengthened with CFRP plates were used to evaluate those of the steel beam specimens. The correction factor α₁ was modified based on the transformed section method, and an additional correction factor φ was introduced into the expressions. Three-dimensional FE modeling was conducted to calculate the stress intensity factors. Numerous combinations of the specimen geometry, crack length, CFRP thickness and Young's modulus, adhesive thickness and shear modulus were analyzed. The numerical results were used to investigate the variations in the stress intensity factor and the additional correction factor φ. The proposed expressions are a function of applied stress, crack length, the ratio between the crack length and half the width of the tension flange, the stiffness ratio between the CFRP plate and tension flange, adhesive shear modulus and thickness. Finally, the proposed expressions were verified by comparing the theoretical and numerical results.

• Computers and Concrete
• /
• 제15권1호
• /
• pp.1-20
• /
• 2015

Many existing reinforced concrete (RC) columns in structures tend to become substandard RC ones due to updated standards or environmental changes. These substandard columns may alter the behaviors of the whole structure and therefore are in urgent need of seismic retrofitting. Owing to their superior advantages, carbon fiber reinforced polymer (CFRP) composites are widely used to retrofit RC columns. The applications mainly focus on various substandard RC columns, but few deals with substandard columns with deteriorated concrete, especially damaged by earthquake. The purpose of this paper is to investigate the seismic behaviors of CFRP reinforced partially deteriorated RC columns and to evaluate the effect of CFRP sheets on them. Six flexure-dominant columns were tested under a constant axial load and transverse cyclic displacements. It is found that the seismic behaviors of partially deteriorated columns can be recovered by wrapping CFRP sheets on them. Numerical analysis is then conducted using finite element methods and verified with experimental results. The effects of the axial load ratio, the ratio of the thickness of CFRP sheet to the column diameter, and the slenderness ratio on the seismic behaviors of CFRP reinforced RC columns are evaluated. Finally, a method is proposed to determine the required thickness of CFRP sheet.

• 한국공작기계학회논문집
• /
• 제12권6호
• /
• pp.8-13
• /
• 2003

CFRP composite has a lot of merits such as mechanical characteristic, light weight and thermal resistance. For these merits CFRP is applied to so many industrial area. In order for the composite materials to be used in the aircraft structures or machine elements, accurate surfaces for bearing mounting or joints must be provided, which require precise machining. In this paper, the relationship between the stack thickness and drill diameter is examined from the drilling experiment, which is the drilling of 16, 32, 48p1ies specimen with the ${\phi}8$, ${\phi}10$, ${\phi}12mm$ cemented carbide drill. The results are analyzed with consideration of cutting force, stack thickness and drill diameter.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2003년도 춘계학술대회 논문집
• /
• pp.190-195
• /
• 2003

CFRP composite has a lot of merits such as mechanical characteristic, light weight, and thermal resistance. For these merits CFRP is applied to so many industrial area. In this paper, the relationship between the stack thickness and drill diameter is examined from the drilling experiment, which is the drilling of 16, 32, 48 plies specimen with the $\phi$8, $\phi$10, $\phi$12mm cemented carbide drill. The results are analyzed with consideration of cutting force, stack thickness and drill diameter.

• 한국강구조학회 논문집
• /
• 제26권3호
• /
• pp.169-176
• /
• 2014

본 연구에서는 콘크리트 충전 각형강관 (CFTP) 단주기둥에 CFRP 쉬트를 횡방향으로 보강하고 중심축하중 실험을 수행하였다. 실험변수는 b/t, CFRP쉬트 보강겹수이며, 총 6개의 실험체가 제작되었다. 실험변수로 사용된 판폭두께비는 b/t는 60, 80, 100이고 CFRP쉬트는 3겹 보강하였다. 실험결과 판폭두께비 100 실험체에서 CFRP쉬트 3겹 보강을 통해 내력을 16% 상승시켜 보강효과를 검증하였다. 내력 저하율을 검토한 결과 국부좌굴이 발생하지 않는 단면강도를 기준으로 최대 41%정도 내력이 저하되었으나, CFRP보강을 통해 32% 정도의 내력이 저하되어 보강효과를 검증할 수 있었다. 하중-변형를 관계를 보면 강재는 항복강도 이전에 국부좌굴이 발생하였으며, CFRP쉬트의 보강을 통해 국부좌굴을 지연시킴을 확인하였다.

• Steel and Composite Structures
• /
• 제21권6호
• /
• pp.1307-1325
• /
• 2016

Nonlinear behavior of two-span, continuous composite steel-concrete girders strengthened with Carbon Fiber Reinforced Polymers (CFRP) bonded to the top of concrete slab over the negative moment region was evaluated using a non-linear Finite Element (FE) model in this paper. A three-dimensional FE model of continuous composite girder using commercial software ABAQUS simulated and validated with experimental results. The interfacial regions of the composite girder components were modeled using suitable interface elements. Validation of the proposed numerical model with experimental data confirmed the applicability of this model to predict the loading history, strain level for the different components and concrete-steel relative slip. The FE model captured the different modes of failure for the continuous composite girder either in the concrete slab or at the interfacial region between CFRP sheet and concrete slab. Through a parametric study, the thickness of CFRP sheet and shear connection required to develop full capacity of the continuous composite girder at negative moment zone have been investigated. The FE results showed that the proper thickness of CFRP sheet at negative moment region is a function of the adhesive strength and the positive moment capacity of the composite section. The shear connection required at the negative moment zone depends on CFRP sheet's tensile stress level at ultimate load.

• Steel and Composite Structures
• /
• 제23권4호
• /
• pp.385-397
• /
• 2017

Currently, CFRP (Carbon Fiber Reinforced Polymer) plate bonding is used quite extensively as a strengthening method. In this technique, a composite CFRP plate or sheet of relatively small thickness is bonded with an adhesion material to steel or concrete structure in order to improve its structural behavior and strength. The sheets or plates do not require much space and give a composite action between the adherents. In this study, the rotation capacity of CFRP-strengthened cold-formed steel (CFS) beams has been evaluated through numerical investigation. Studies on different structural levels have been performed. At the beam level, C-section has been adopted with different values of profile thickness, web height, and flange width. At the connection level, a web bolted moment resistant type of connection using through plate has been adopted. In web-bolted connections without CFRP strengthening, premature web buckling results in early loss of strength. Hence, CFRP sheets and plates with different mechanical properties and geometric configurations have been examined to delay web and flange buckling and to produce relatively high moment strength and rotation capacity. The numerical results reveal that CFRP strengthening may increase strength, initial stiffness, and rotation capacity when compared with the case without strengthening.