Bond stress between cast-in-place ductile fiber reinforced cementitious composites and CFRP plank were experimentally analyzed. As failure shape, the mixture of failure between CFRP plank and epoxy, and failure between concrete and epoxy was shown. In case of RFCON from the suggested simple bond slip relationship, the maximum average bond stress was 5.39MPa, the initial slope was 104.09MPa/mm, and the total slip length was 0.19mm. PPCON showed the maximum average bond stress of 4.31MPa, the initial slope of 126.67MPa/mm, and the total slip length of 0.26mm, while RFCON+ appeared to have 8.71MPa, 137.69MPa/mm, 0.16mm. PPCON+ had 6.19MPa maximum average bond stress, 121.56MPa/mm initial slope, and 0.34mm total slip length. To comprehend the behavior of composite structure of FRP and concrete, local bond slip relation is necessary, and thus a simple relation is suggested to be easily applied on hybrid composite system

Nowadays, the study of CFRP reinforced with carbon fiber is focused on improving the the mechanical property. The study on the fracture data of CFRP are not properly made out than that of the general mechanical joint. In this study, the fracture property of mode 1 at the same condition of tensile experiment is investigated by applying the layer angle to laminated CFRP with the thickness of 15 mm. When the reaction forces until dropping out the bonded surface are compared with the cases of the layer angles of 0°, 45° and 60°, the reaction force is shown to be most and the elapsed time until dropping out the bonded surface is longest at that of 45°. The deformation energy is also shown to have the highest value by dropping out the adhesive interface. As the basis of the analysis result of this study, the most safety with fracture resistance is shown in the case of 45°. the bonded structure applying the appropriate layer angle is thought to have the structural safety.

CFRP has the high strength and low weight. But it tends to be frail if it is applied with the mechanical bonding method using weld, rivet or bolt. So, the chemical bonding method using the special adhesive has been utilized. By applying the bonding method with the adhesive, this paper investigates the mechanical property of DCB specimen bonded with the type of mode 2 through the simulation analysis. Four kinds of specimen thicknesses are 25mm, 35mm, 45mm and 55mm in this study. The mechanical behaviors of specimens due to the forced displacements are investigated as the distributions of equivalent stresses. The reaction force becomes higher as the specimen thickness is increased. The result of this study about the fracture property of adhesive joint is thought to be contributed to the safe design of structure with CFRP.

일반적으로 CFRP 레저선박의 상부구조물은 동급전장 타 선박보다 매우 작은 경향을 보이고 있는데, 이는 풍압면적에 의한 횡요저항력과 밀접한 관련이 있는 것으로 알려져 있다. 본 연구에서는 CFRP 레저선박의 이러한 상부구조물 형상 특성을 풍압면적 변화에 따른 복원안정성 분석을 통해 파악하고자 한다. GFRP 레저선박과 CFRP 레저선박의 선체 및 상부구조물 형상 특성을 상호 비교하고, CFRP 레저선박의 상부구조물 형상변화를 통해 그 변화가 복원안정성에 미치는 영향에 대해 분석하였다. 이를 위해 GFRP, CFRP 레저선박 총 10척의 형상을 비교, 분석하여 선체와 상부구조물 간의 형상 추세를 파악하였고, ISO 12217에 따른 횡요저항력 추정 및 복원안정성 평가 프로그램 개발을 통해 상부구조물의 형상 변화와 복원안정성 간의 관계를 분석하였다. 연구결과, CFRP 레저선박의 풍압면적 분포경향은 GFRP 레저선박과 비슷하였으나, 상대적으로 상부구조물 형상 비율은 절반정도 크기에 그치는 경향을 보였다. 또한 CFRP 레저선박의 상부구조물 크기를 동급전장의 GFRP 선박 상부구조물 면적 비율 이상(10%) 증가시키는 경우 횡요저항력에 의한 복원성능에 문제가 발생하는 것을 확인할 수 있었다.

For the last decade many bridges and buildings have experienced flexural strengthening with the fiber reinforced polymer(FRP) bonding system, demands for increasing heavy traffic loads and the changing of the code application. Of the many strengthening systems, NSM(near surface mounted) system with FRP has become attractive and popular way of strengthening for the existed RC structures and many studies and applications of this technique have significantly increased all over the world. Meanwhile, polymer mortar that contains much of the same ingredients as cement but includes the addition of certain polymer resins for enhancing desired physical properties, has been used as an alternative adhesive. This paper focuses on flexural behaviour of CFRP-bar NSM system with variables such as kinds of adhesive, anchorage, sectional aspect ratio. Based on the test results and test-to -predicted ratio, this paper provides researchers and practical engineers a fundamental knowledge and intuition.

해양레저 활동의 범위가 점차 원거리 항해로 확대되면서 거주가 가능한 크루즈보트가 각광받고 있다. 해양레저산업 선진국인 유럽, 북미의 경우 미려한 디자인, 인간공학적 구조 그리고 경량선체 소재 채택을 통한 연료효율 향상 등 크루즈보트의 설계와 제작에 있어 이미 경쟁력을 확보하고 있다. 반면, 국내의 경우 소형 레저보트 중심의 개발, 건조가 이뤄지고 있으며, 선체소재 또한 유리섬유강화복합재료(GFRP)가 대부분을 차지하고 있다. 본 연구에서는 원양항해가 가능한 50피트급 탄소섬유강화복합재료(CFRP) 선체 크루즈보트의 설계 및 특성에 관한 연구를 수행하였다. CFRP 선체 레저보트의 선형특성을 분석하여 설계선(MMU-C.B)의 선형을 제안하였으며, 이를 기반으로 CFRP 크루즈 보트의 설계모델을 구축하였다. 또한 GFRP 레저선박의 모형시험결과와 MMU-C.B 설계결과의 조선공학적 비교검토를 통해 설계선의 형상 그리고 저항 및 활주자세 특성을 분석하였다.

Because of the inherent flexibility in their design for improved material properties, composites have wide applications in aerospace vehicles and automobiles. The purpose of this study is to investigate the energy absorption characteristics of CFRP(Carbon Fiber Reinforced Plastics)tubes on static and impact tests. Static compression tests have been carried out using the static testing machine(Shin-gang buckling testing machine)and impact compression tests have been carried out using the vertical crushing testing machine. When such tubes were subjected to crushing loads, the response is complex and depends on the interaction between the different mechanisms that control the crushing process. The collapse characteristics and energy absorption were examined. Trigger and interlaminar number affect the energy absorption capability of CFRP tubes.

In this study a hybrid safety barrier system consisting of steel rail and carbon fiber reinforced polymer (CFRP) post is considered. W hile CFRP post is selected for impact energy reflection due to its high strength, steel rail is selected for impact energy absorption due to its high ductility. A numerical model considering the elastoplastic behavior of steel is formulated to simulate the dynamic responses of the hybrid system subject to an impact load. A hybrid roadside guard rail system of steel rail and CFRP post is proposed and analyzed with a case study. The numerical model for the hybrid roadside guard rail system is used to find optimized design of the proposed hybrid system.

In this study, carbon/epoxy composite DCB(double cantilever beam) specimens based on K-means clustering and wavelet transform analyses are presented. For the fracture Mode I, the fiber orientation θ = [0 ]24 and θ = [±45]12 both shown up stable crack growth in DCB testing. For the fiber orientation θ = [0 ]24 , the continuous type AE signal showed at central frequency 130～270kHz, which means that matrix micro cracking was occurred. The Burst type AE signal was occurred at central frequency 200～300kHz due to fiber bridging and fiber breaking. Other burst type AE signals were occurred at central frequency 130～180kHz with very high amplitude due to fiber bridging. For the fiber orientation θ = [±45]12 , the burst type signal showed at central frequency 220～300kHz, which means that fiber breaking was occurred. Mixed type of burst and continuous signals were captured at central frequency 250～480kHz due to fiber friction.

Carbon fiber reinforced polymeric plastic (CFRP) can be used for the deteriorated reinforced concrete members. CFRP reinforcement method, which is one of the reinforcement methods, can improve the strength and durability of reinforced concrete member. CFRP reinforcement method has been proved that it has sufficient effect on the flexural strengthening of reinforced concrete flexural member through numerous previous researches. In this paper, we present the analytical result of investigation pertaining to the CFRP reinforcing effect on the singly reinforced and doubly reinforced rectangular flexural members and T-shape singly reinforced flexural member. The analytical study is performed according to the code by ACI Committee 440 and previous research results.

In this study a hybrid system consisting of steel and carbon fiber reinforced polymer (CFRP) is considered. While CFRP is selected for impact energy reflection due to its high strength, steel is selected for impact energy absorption due to its high ductility. A numerical model considering the elastoplastic behavior of steel is formulated to simulate the dynamic responses of the hybrid system subject to an impact load. A hybrid roadside guard rail system of steel rail and CFRP post is proposed and analyzed with a case study. The numerical model for the hybrid roadside guard rail system is used to find optimized design of the proposed hybrid system for future study.

강철보다 10배 강하지만, 무게는 5분의 1 비행기부터 컴퓨터까지 ‘꿈의 신소재’ 탄소섬유 전쟁 －탄소 섬유로 미래를 지배하라 “가볍게 이동하며 연비는 향상” 항공기⋅車에 주로 쓰였지만 이젠 아파트⋅풍력발전도 사용 －한국, 일본을 잡아라 도레이 등 日업체들이 세계 빅3 꾸준한 투자로 34년만에 이익 태광⋅효성 등 한국도 뛰어들어… 일본처럼 길게 보고 승부해야 지난 9월 IT업계에 애플이 맥북과 아이패드 외장재로 신소재를 사용할 것이란 소문이 퍼져 업계의 비상한 관심을 끌었다. 애플의 새 제품이 소재와 디자인 혁신을 주도, 또 한 번 시장을 뒤흔들 것이란 내용이었다. 얼마 뒤 일본 IT 웹사이트인 맥오타카는 애플이 이 신소재를 사용한 자전거 제조업체 대표를 복합소재 수석 엔지니어로 채용했다고 보도했다. 애플이 입을 닫아 사실 여부는 확인되지 않았지만 소문은 신빙성을 더했다. 여기서 말한 신소재는 탄소섬유(Carbon Fiber)다. 강철보다 강도는 10배 높으면서 무게는 5분의 1에 불과해 ‘꿈의 신소재’로 불린다. 거의 100%에 가까운 탄소원자로 구성된 섬유로한 가닥의 탄소섬유 실에는 수천 가닥의 탄소섬유가 꼬여져 있어 강도가 높다.

This study presents the effectiveness of a composite structure at improving blast resistance. The proposed composite structure consists of carbon fiber reinforced polymer (CFRP) and steel layers. While CFRP layer is used for blast energy reflection due to its high strength, steel layer is used for blast energy absorption due to its high ductility. A dynamic model is used to simulate the elastoplastic behavior of the proposed composite structure subject to blast load. Considering the magnitude variations of a blast event, the probability of failure of each layer is evaluated using reliability analysis. By assigning design probability of failure of each layer in the composite structure, the thickness of layers is optimized. A case study for the design of CFRP-steel composite structure subjected to an uncertain blast event is also presented.

This paper presents experimental studies aiming at evaluation of structural behaviors of RC (Reinforced Concrete) beams externally strengthened with taper ended CFRPs(Carbon Fiber Reinforced Polymers). Experiments are performed with RC beams having different numbers of CFRP layers and length of each layer. The beams are subjected to four point-bending with simply supported condition. Test results of taper ended CFRPs and non-tapered CFRPs are compared and the better strengthening effect is observed from tapered ended CFRPs.

본 연구에서는 강재가 맞대기 이음으로 연결될 경우 CFRP(Carbon Fiber Reinforced Plastic) 쉬트(sheet)를 맞대기 이 음부에 접착할 경우 강재 및 CFRP 쉬트에 발생하는 응력을 해석하였다. CFRP 쉬트로 보강한 경우 접착제의 두께, 강재와의 접착 길이, CFRP 강도 변화를 매개변수로 사용하여 이 매개변수에 변화에 따른 이음부의 응력분포를 분 석하였다. 또한 CFRP를 여러 층으로 접착할 경우 각 층의 강도를 다르게 변화시켜 맞대기 이음부에 유리한 응력분 포를 나타내는 CFRP의 강도를 제시하였다. 본 연구를 위해 빠른 수렴성을 가지며 왜곡된 요소형상에서도 정확한 응력결과를 보이는 강화변형률장(Enhanced Assumed Strain Field)을 사용한 평면변형률 유한요소에 대한 프로그램을 작성하였다.

The CFRP composite has a lot of merits such as mechanical characteristic, light and thermal resistance. For these merits, CFRP is applied to so many industrial area. In order to use the composite materials in the aircraft structures or machine elements, accurate surfaces for bearing mounting or joints must be provided, which require precise ,machining. In this study, the specimens differentiating the stacking sequence of 5kinds were used. When drilling the carbon fiber reinforced plastics, it was checked on whether the stacking sequence reached any effect on the cutting force. Also relationship between the drill diameter is examined from the drilling experiment, which is the drilling of Fabric, Unidirectional specimen with ∅6mm, ∅10mm, ∅12mm cemented carbide drill. Considering cutting force and drilling diameter, the results are analyzed.

The Axial compression tests were conducted on FRP strengthened circular CFT short clumns with the test parameters of D/t ratio and the number of FRP sheet ply. The ultimate strength design formula were proposed by applying ACI 440 code for FRP strengthened circular CFT columns.