A Statistical Framework for Selecting Natural Fibre Reinforced Polymer Composites Based on Regression Model

M. Noryani,S.M. Sapuan,M. T. Mastura,M. Y. M. Zuhri,E. S. Zainudin 한국섬유공학회 2018 Fibers and polymers Vol.19 No.5

Material selection is an important stage in the development of products from composites process of automotive component application. Numerious different Multi-Criteria Decision-Making tools have their own strenghts and limitations. This paper presents a framework for material selection of natural fibre reinforced polymer composites by using statistical approach. The framework is developed using statistical methods which are simple, multiple and stepwise regression for the material selection process. The performance of potential material is investigated by a statistical analysis such as coefficient of correlation, coefficient of determination and analysis of variance. A case study to select the best composite of parking brake lever is applied to this framework. End results revealed that kenaf reinforced polypropylene is the best candidate for construction of automotive parking brake lever component. The best possible of statistical model for material selection of the composite can be referred by design engineer in composite industry for a multiple application. Moreover, the proposed framework is an aid to help engineers and designers to choose most suitable material.

Equivalent reinforcement isotropic model for fracture investigation of orthotropic materials

Mahdi Fakoor,Roham Rafiee,Shahab Zare 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.30 No.1

In this research, an efficient mixed mode I/II fracture criterion is developed for fracture investigation of orthotropic materials wherein crack is placed along the fibers. This criterion is developed based on extension of well-known Maximum Tensile Stress (MTS) criterion in conjunction with a novel material model titled as Equivalent Reinforced Isotropic Model (ERIM). In this model, orthotropic material is replaced with an isotropic matrix reinforced with fibers. A comparison between available experimental observations and theoretical estimation implies on capability of developed criterion for predicting both crack propagation direction and fracture instance, wherein the achieved fracture limit curves are also compatible with fracture mechanism of orthotic materials. It is also shown that unlike isotropic materials, fracture toughness of orthotic materials in mode I cannot be introduced as the maximum load bearing capacity and thus new fracture mechanics property, named here as maximum orthotropic fracture toughness in mode I is defined. Optimum angle between crack and fiber direction for maximum load bearing in orthotropic materials is also defined.

Design of hole-clinching process for joining of dissimilar materials - Al6061-T4 alloy with DP780 steel, hot-pressed 22MnB5 steel, and carbon fiber reinforced plastic

Lee, C.J.,Lee, J.M.,Ryu, H.Y.,Lee, K.H.,Kim, B.M.,Ko, D.C. Elsevier 2014 Journal of materials processing technology Vol.214 No.10

The mechanical joining of dissimilar materials is a key technology in the automotive industry as it enables the realization of car bodies that incorporate multiple materials. However, it remains difficult to join materials such as aluminum alloy to high-strength/low-ductility materials such as advanced high-strength steel, hot-pressed steel, and carbon fiber reinforced plastic by using joining methods that are based on forming technology. The purpose of this study is to develop a new joining process, called ''hole clinching,'' for these material combinations. In the hole-clinching process, the ductile material is positioned uppermost and the brittle material-into which a hole is formed-is positioned below that. The upper sheet is indented into a die cavity through the hole in the lower sheet and spread so that the two sheets interlock geometrically. In this study, hole-clinching tools were designed based on the geometrical relationship between the forming volume and the joint strength. Finite element analysis and practical experiments were performed to verify the practicality of the hole-clinching process. The cross-sections of the hole-clinched joints formed in our experiments were in good agreement with the results of the finite element analysis. Then, a single-lap shear test was performed to evaluate the joint strength. The hole-clinched joints, regardless of the material combinations, provided a joint strength in excess of the desired 2.5kN. These results point to the applicability of the hole-clinching process to the joining of dissimilar materials.

확률분포를 이용한 취성재료 특성의 탄소섬유보강폴리머 인장물성평가 및 보정

김윤곤 한국구조물진단유지관리공학회 2019 한국구조물진단유지관리공학회 논문집 Vol.23 No.3

Carbon Fiber Reinforced Polymers (CFRP) has widely utilized as a material for rehabilitation because of its light-weight, deformability and workability. Because CFRP is brittle material whereas steel is ductile, it is inappropriate to apply conventional design approach for steel reinforcement. For ductile material, the behavior of combined elements is on average of that of unit element due to the stress redistribution between elements after yielding. Therefore, the mean value of the stress of combined elements is equal to that of unit element and the standard variation is smaller. Therefore, although the design value can increase, it is used as constant value because it is conservative and practical approach. However, for brittle material, the behavior of combined elements is governed by the weaker element because no stress redistribution is expected. Therefore, both the mean value and standard variation of the stress of combined elements decreases. For this reason, the design value would decrease as the number of element increases although it is eventually converged. In this paper, in brittle material, it is verified that the combination of unit element with normal distribution results in combined element with weibull distribution, so the modifying equation of mechanical properties is proposed with respect to the area load applied. 탄소섬유보강폴리머(CFRP)는 경량이며, 성형성 및 작업성이 뛰어나 보수보강재료로서 널리 사용되고 있다. 하지만, 연성재료인 철근과는 달리 CFRP는 취성재료이므로, 철근에서 사용되는 전통적인 설계접근 방법을 적용하는 것은 부적합하다. 연성재료인 철근은 항복이후 요소사이의 응력재분배가 이뤄져 복합요소의 거동은 평균화된다. 따라서 복합요소의 응력 평균은 단위요소의 평균과 같고, 표준편차는 더 작아진다. 따라서 연성재료의 설계값은 증가시킬 수 있으나, 안전측, 실무적 접근에서 고정값을 사용한다. 반면 취성재료의 경우, 응력재분배를 기대하기 어려워 복합요소의 거동은 더 약한 요소에 의해 결정된다. 이에 복합요소의 응력의 평균값과 표준편차는 감소한다. 따라서 취성재료의 설계값은 요소수가 증가할수록 감소한다. 이 논문에서는 취성재료에서 정규분포를 가지는 단위요소가 요소 결합에 따라 와이블 분포를 가지게 됨을 증명하고, 이를 반영하여 하중이 작용하는 면적에 따른 물성치의 보정식을 제안하였다.

복합소재를 활용한 B필러 강화재의 구조해석 및 설계

강지헌 ( Ji Heon Kang ),김건우 ( Kun Woo Kim ),장진석 ( Jin Seok Jang ),김지욱 ( Ji Wook Kim ),양민석 ( Min Seok Yang ),구윤식 ( Yoon Sik Gu ),안태민 ( Tae Min Ahn ),권순덕 ( Sun Deok Kwon ),이재욱 ( Jae Wook Lee ) 한국복합재료학회 2021 Composites research Vol.34 No.1

본 논문은 차량에 사용되는 B필러의 강화재를 기존의 스틸 소재에서 CFRP(Carbon Fiber Reinforced Plastics)와 GFRP(Glass Fiber Reinforced Plastics)로 대체하여 경량화하는 것이 목표다. 이를 위해서는 무게는 감소시키면서 기존 B필러를 대체할 수 있는 구조안정성을 확보해야 한다. 기존 B필러는 스틸 아우터(outer)를 포함하여 다양한 형상의 스틸 강화재로 구성되며, 이와 같은 스틸 강화재 중 2가지의 스틸 강화재를 복합재로 대체하고자 한다. 이와 같은 스틸 강화재는 강화재 각각을 따로 제작하여 용접을 통해 결합되지만, 복합재 강화재는 패치(patch) 형태의 CFRP와 리브(rib) 구조의 GFRP를 활용하여 압축과 사출 공정을 통해 한번에 제작된다. CFRP는 B필러의 고강도부에 부착되어 측면 하중에 저항하도록 하였으며, GFRP 리브는 위상 최적화(Topology optimization) 기법을 통해 비틀림과 측면 하중을 저항하도록 설계하였다. 구조해석을 통해 기존 스틸 강화재와 비교 분석을 수행하였고, 경량화율을 산출하였다. This paper aims to reduce weight by replacing the reinforcements of the B-pillar used in vehicles with CFRP(Carbon Fiber Reinforced Plastics) and GFRP(Glass Fiber Reinforced Plastics) from the existing steel materials. For this, it is necessary to secure structural stability that can replace the existing B-pillar while reducing the weight. Existing B-pillar are composed of steel reinforcements of various shapes, including a steel outer. Among these steel reinforcements, two steel reinforcements are to be replaced with composite materials. Each steel reinforcement is manufactured separately and bonded to the B-pillar outer by welding. However, the composite reinforcements presented in this paper are manufactured at once through compression and injection processes using patch-type CFRP and rib-structured GFRP. CFRP is attached to the high-strength part of the B-pillar to resist side loads, and the GFRP ribs are designed to resist torsion and side loads through a topology optimization technique. Through structural analysis, the designed composite B-pillar was compared with the existing B-pillar, and the weight reduction ratio was calculated.

DEVELOPMENT AND ANALYSIS OF BUS WITH COMPOSITE-MATERIAL-REINFORCED FRAMES

Tso-Liang Teng,Cho-Chung Liang,Hui-Min Chu 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.5

The bus frame structures suffer serious deformation or fracture and then damage the survival space of passengers. The superstructure of a bus is a frame member that supports the vehicle’s load and incorporates other parts for strength enhancement and impact absorption. Therefore, superstructures of bus play an essential role in protecting passengers in case of rollover accidents. Currently, the frames of large passenger vehicles are mostly manufactured using steel materials. The selection of a composite material that exhibits lightweight and outstanding structural strength has become an imperative topic in research on the reinforcement of large passenger vehicles’ frames. This study examined a vehicle frame reinforced using steel coated with composite materials. According to the relevant regulations in ECE R66 on the superstructure strength of large passenger vehicles, the LS-DYNA simulation was employed to perform structural analysis. A composite-materialreinforced frame was employed to simulate the crush test, thereby evaluating the effect of such reinforcement on enhancing the strength of vehicle frames. Finally, a rollover simulation test was performed according to ECE R66 on a vehicle whose entire frame was constituted by composite-material-reinforced steel. This study’s proposed vehicle frame material for design improvements can serve as references for manufacturers of large passenger vehicle bodies to improve the quality of their product development.

건설자재 가격 변동에 따른 공동주택 분양가 변화 분석

최열(Choi Yeol),임하경(Yim Ha Kyoung),박봉운(Park Bong Woon) 대한토목학회 2009 대한토목학회논문집 D Vol.29 No.6D

본 연구는 2001년부터 2008년까지 건설자재 가격의 변동에 따른 부산시 공동주택의 분양가 변동을 분석하고자 하였다. 주요 분석결과는 다음과 같다. 첫째, 본 연구는 공동주택의 대표 건설자재로 건축비에서 가장 큰 비중을 차지하는 철근과 레미콘, PHC파일, 동관 총 4가지 자재를 대상으로 분석을 실시하였는데, 철근과 동관의 경우 각각 연평균 14.03%, 14.91%.로 높은 가격 상승을 보인 반면, 레미콘은 연평균 0.86%, PHC파일은 2.41%의 상승으로 거의 가격 변동이 없는 것으로 나타나 자재별 가격 변동의 격차가 크다는 사실을 알 수 있었다. 둘째, 공동주택의 분양가와 건설자재 가격의 변동에 관한 연관성을 분석한 결과에 의하면 철근과 레미콘, PHC 파일, 동관 모두 공통적으로 3개월 시차에 의한 영향이 가장 높게 나타났으며, 6개월 시차, 9개월 시차를 둘수록 그 영향력은 조금씩 감소했다. This study analyzed the fluctuation of the construction material cost from 2001 to 2008 in Busan to examine the effect of the fluctuation of the construction material cost on lotting price of the multi family attached house. The major findings are as follow. First, as the result of the analysis on four materials such as reinforced bar, remicon, PHC piles, Copper Tubes, those take largest portion of construction cost, it was found that the there is wide difference in price fluctuation of the each materials. The reinforced bar and Copper Tubes showed high price increase by an average 14.03% and 14.91% per year while remicon, PHC piles remained almost unmoved by an average 0.86% and 2.41 %. Second, According to the result of the analysis on the mutuality between the fluctuation of the construction material cost and the lotting price of the multi-family attached house, it was found that the fluctuation of the construction material cost have the most enormous effect on the sale price of the multi-family attached house, when there is 3 month time lag in reinforced bar, remicon, PHC piles, Copper Tubes, commonly. Also this mutuality continues to 6 month, 9 month and I year, although it decrease a little bit.

강성도에 주목한 표층처리공법으로 개량된 초연약지반의 지지력 산정방법

함태규(Tae-Gew Ham),조삼덕(Sam-Deok Cho),양기석,유승경(Seoung-Kyoung You) 한국토목섬유학회 2010 한국토목섬유학회 학술발표회 Vol.2010 No.11

This study, as basic research which was intended to develope the surface reinforcement method using reinforcement material which is applicable to very soft ground in Korea, was aimed at proposing the design parameter for the surface ground improvement method. To that end, a wide width tensile test using geotextile, geogrid and steel bar (substitute for bamboo) and 49 kinds of the laboratory model tests were conducted. And the result the study suggested β<SUB>s</SUB>, the stiffness coefficient to evaluate the stiffness effect of reinforcement materials. Then, it was also found that the stiffness coefficient, β<SUB>s</SUB> as the testing constant would be appropriate as high as 1.0, 1.1 and 1.5 for geotextile, geogrid and steel bar, respectively. And It was evaluated that the stiffness effect affecting reinforcement improvement effect would be reduced as the thickness of embeded depth increases and that RFe, the stiffness effect reduction coefficient would have positive correlation with H/B. Finally, it was confirmed that the bearing capacity gained from the method to calculate bearing capacity, which was suggested in the study, would almost correctly estimate the capacity, demonstrating the appropriateness of the proposed bearing capacity calculation method.

Application of FE approach to deformation analysis of RC elements under direct tension

Ronaldas Jakubovskis,Rimantas Kupliauskas,Arvydas Rimkus,Viktor Gribniak 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.3

Heterogeneous structure and, particularly, low resistance to tension stresses leads to different mechanical properties of the concrete in different loading situations. To solve this problem, the tension zone of concrete elements is reinforced. Development of the cracks, however, becomes even more complicated in the presence of bar reinforcement. Direct tension test is the common layout for analyzing mechanical properties of reinforced concrete. This study investigates scatter of the test results related with arrangement of bar reinforcement. It employs results of six elements with square 60×60 mm cross-section reinforced with one or four 5 mm bars. Differently to the common research practice (limited to the average deformation response), this study presents recordings of numerous strain gauges, which allows to monitor/assess evolution of the deformations during the test. A simple procedure for variation assessment of elasticity modulus of the concrete is proposed. The variation analysis reveals different deformation behavior of the concrete in the prisms with different distribution of the reinforcement bars. Application of finite element approach to carefully collected experimental data has revealed the effects, which were neglected during the test results interpretation stage.

실내모형실험을 통한 표면건조층이 표층처리된 초연약지반의 침하거동에 미치는 영향분석

함태규(Tae-Gew Ham),서세관(Se-Gwan Seo),조삼덕(Sam-Deok Cho),이승원(Seung-Won Lee),양기석,유승경(Seoung-Kyoung You) 한국토목섬유학회 2009 한국토목섬유학회 학술발표회 Vol.2009 No.4

In this study, eight times of indoor model experiments reproducing site conditions were performed to analyze the influence of dry surface layer(crust) in the settlement behavior of soft dredged ground strengthened with surface reinforcement material. According to the results of the experiments, the settlement reduced according to the increase of the value of stiffness normalized into tensile strength, showing that the settlement behavior of surface reinforced, soft ground heavily depends upon the stiffness, by a linear relation at -0.37 slope in log-log coordinates. For the geotextiles with relatively smaller stiffness, it was verified that dry surface layer contributes to the load distribution effect of reinforcement material changing the surface behaviors including the shift of the position of the maximum rising from the center and decrease in settlement.