자동 섬유 적층(AFP)을 활용한 열가소성 복합재의 공정 변수에 따른 기계적 물성 평가

성정원,최현석,권보성,오세운,이상민,남영우,권진회 한국복합재료학회 2019 Composites research Vol.32 No.5

In this study, the effects of the additional processing parameters on the mechanical properties of thermoplastic composites fabricated with automated fiber placement (AFP) were evaluated. Annealing and vacuum bag only processes were then performed on the manufactured thermoplastic composites, respectively. For verification, the crystallinity was measured by differential scanning calorimetry (DSC), confirming the variation of semi-crystalline thermoplastic composite according to the process conditions. The void content of thermoplastic composites was evaluated by matrix digestion method while microscopic examination confirmed the porosity distribution. The interlaminar shear strength test was conducted for three different process parameters (VBO, annealing, and no treatment). A comparison of the three tested strengths was made, revealing that the porosity value had larger effect on the mechanical properties of the thermoplastic composite compared to the degree of crystallinity. Additionally, when thermoplastic composite melted up, the pores were continuously removed under vacuum process; the removal of the pores resulted in an increase of the interlaminar shear strength. 본 연구에서는 자동 섬유 적층(AFP) 장비로 제작한 열가소성 복합재에 대하여 추가 공정을 수행한 후 기계적 물성에 미치는 영향을 평가하였다. 제작을 위한 기초 연구로써 AFP의 공정 변수를 통해 열가소성 복합재를 제작하였으며 제작된 열가소성 복합재에 어닐링(Annealing) 및 진공백(Vacuum bag only) 공정을 수행하였다. 추가 공정 후 검증을 위해 결정화도 및 기공률 측정을 수행하였다. 결정화도는 시차 주사 열량 측정법(Differential scanning calorimetry)을 통해 측정하였으며 반 결정 구조인 열가소성 복합재의 공정 조건에 따른 결정화도 변화를 확인하였다. 기공률 측정을 위해 수지 용해를 수행하였으며 현미경 촬영을 통해 기공 분포를 확인하고 수지 용해법을 통해 기공률을 계산하여 공정 조건에 따른 기공률 변화를 관찰하였다. 검증 후 수행한 층간 전단 강도 시험 결과 AFP로 제작한 열가소성 복합재의 경우 결정화도 보다 기공률 값이 기계적 물성에 더 많은 영향을 미쳤다. 또한 진공백 공정을 통해 열가소성 복합재를 녹는점까지 도달시켰으며 진공상태에서 지속적으로 열가소성 복합재 내의 기공을 제거함에 따라 층간 전단 강도가 증가하는 것을 확인하였다.

Microstructural analysis and experimental investigation of mechanical properties of epoxy based hybrid composite reinforced with flax, sisal and luffa fibre

S. Sridhar,S. Nandhakumar,M. Nallusamy,R. Maguteeswaran 한양대학교 세라믹연구소 2022 Journal of Ceramic Processing Research Vol.23 No.4

The glass fiber provides lots of health problem during its production and testing. Our aim is to replace the glass fiber bynatural fiber that will survive for an automotive industry by easily recycling and excellent strength to weight ratio. This workis the investigation of the hybrid composite by reinforcing it with flax, Luffa fiber & sisal fiber. Also in this work, the naturalfibers are treated to remove the impurities and increase the bonding strength and tensile strength. The mechanical andphysical properties for the above hybrid composites are investigated.

탄소섬유 표면에의 고분자 전착과 복합재료 물성(I) - MVEMA와 EMA의 전착 -

김민영,김지홍,김원호,김부웅,황병선,최영선,Kim, Minyoung,Kim, Jihong,Kim, Wonho,Kim, Booung,Hwang, Byungsun,Choi, Youngsun 한국공업화학회 1998 공업화학 Vol.9 No.6

탄소섬유 복합재료의 층간전단 강도의 손상없이 충격강도를 향상시키기 위하여 반응성을 가진 유연한 고분자 물질 (MVEMA(poly(methyl vinyl ether-co-maleic anhydride)) 및 EMA (poly(ethylene-co-maleic anhydride)) 전착을 이용하여 탄소섬유와 에폭시 기지재료 사이에 계면상으로 도입하는 방법을 고려하였다. 따라서 계면상 물질의 MVEMA 및 EMA의 탄소섬유에의 전착수율에 대한 공정변수의 영향을 체계적으로 평가하였다. 염기성 수용액상에서 anhydride기를 가진 고분자의 전착 메카니즘은 -OH기의 공격에 의한 $RCOO^-$기의 생성에 기인함을 적외선 분광분석으로 확인하였다. 농도, 전류밀도, 반응시간의 증가에 따라 전착수율이 증가하였으며, 과도한 산소 버블의 발생은 전착된 고분자를 탈착시켜 수율을 감소시켰다. 흐르는 물에서 세척을 할 경우 탄소섬유와의 결합력이 없는 전착고분자는 쉽게 제거되어 0.5 wt% 정도의 전착 고분자만 잔류하였다. An interphase between carbon fiber and epoxy matrix was introduced to increase impact strength of carbon fiber reinforced composites (CFRC) without sacrificing the interlaminar shear strength. Flexible polymers, I. e., MVEMA (poly(methyl vinyl ether-co-maleic anhydride)) and EMA(poly(ethylene-co-maleic anhydride)), which have reactive functional groups were considered as interphase materials. Weight hain of MVEMA and EMA onto the surface of carbon fibers was evaluated by changing the parameters of electrodeposition process. Electrodeposition mechanism of polymers which have anhydride functional group was identified by IR spectroscopy, that is, the generation of $RCOO^-$ functional group by the attack of hydroxide anion in the basic solution was observed. The weight gain was increased by increasing concentration of polymers, current density, and electrodeposition time. However the excess generation of oxygen gas decreased the weight gain by removing the deposited polymers. Washing in the running water easily removed the deposited polymers which are on the fiber surface without bonding, as a results, only 0.5 wt% of deposited polymers are remained.

환경인자에 노출된 탄소섬유/에폭시 복합재의 장기 층간전단강도 예측

윤성호 ( Sung Ho Yoon ),( Ya Long Shi ) 한국복합재료학회 2017 Composites research Vol.30 No.1

본 연구에서는 환경인자에 노출된 탄소섬유/에폭시 복합재의 층간전단강도를 이용하여 장기 성능을 예측하였다. 필라멘트와인딩 공법으로 제작된 층간전단시편은 분위기 온도가 50℃, 70℃, 100℃인 건조 조건과 분위기 온도가 25℃, 50℃, 70℃인 침수 조건에 각각 3000시간까지 노출시켰다. 연구결과에 따르면 분위기 온도가 50℃ 와 70℃인 건조 상태에서는 층간전단강도가 노출시간에 따라 크게 변하지 않지만 분위기 온도가 100℃인 건조 상태에서는 노출시간이 길어지면 후경화로 인해 다소 증가한다. 그러나 분위기 온도가 25℃인 침수 상태의 경우 층간전단강도는 노출 초기에 크게 변하지 않다가 노출시간이 길어지면 감소하고 감소 정도는 분위기 온도가 높아지면 커진다. 각 분위기 온도에 대한 층간전단강도 선형회귀식은 침수 상태에 3000시간까지 노출된 시편에서 얻은 층간전단강도에서 구할 수 있었다. 이들 선형 회귀식을 이용하면 층간전단강도는 분위기 온도가 25℃와 50℃인 경우 측정값의 5.5% 이내, 분위기 온도가 70℃인 경우 측정값의 2.3% 이내로 예측이 가능하였다. 따라서 제시된 성능 예측 절차는 환경인자에 노출된 탄소섬유/에폭시 복합재의 장기 층간전단강도를 잘 예측할 수 있다. The purpose of this study was to predict the long-term performance using the interlaminar shear strength of carbon fiber/epoxy composites exposed to environmental factors. Interlaminar shear specimens, manufactured by the filament winding method, were exposed to the conditions of drying at 50℃, 70℃, and 100℃ and of immersion at 25℃, 50℃, and 70℃ for up to 3000 hours, respectively. According to the results, the interlaminar shear strength did not vary significantly with the exposure time for the drying at 50℃ and 70℃, but it increased somewhat for the drying at 100℃ due to the post curing as the exposure time increased. The interlaminar shear strength of the specimens exposed to the immersion at 25℃ did not change significantly at the beginning of exposure, but it decreased with the exposure time and the degree of decrease increased as the environmental temperature increased. The linear regression equations for the environmental temperatures were obtained from the interlaminar shear strength of the specimens exposed to the immersion for up to 3000 hours. Using these linear regression equations, the interlaminar shear strength was estimated to be within 5.5% of the measured value at 25℃ and 50℃, and 2.3% of the measured value at 70℃. Therefore, the proposed performance prediction procedures can predict well the long-term interlaminar shear strength of carbon fiber/epoxy composites exposed to environmental factors.

Flexural properties, interlaminar shear strength and morphology of phenolic matrix composites reinforced with xGnP-coated carbon fibers

Jong Kyoo Park,Jae Yeol Lee,Lawrence T. Drzal,Donghwan Cho 한국탄소학회 2016 Carbon Letters Vol.17 No.-

In the present study, exfoliated graphite nanoplatelets (xGnP) with different particle sizes were coated onto polyacrylonitrile-based carbon fibers by a direct coating method. The flexural properties, interlaminar shear strength, and the morphology of the xGnP-coated carbon fiber/phenolic matrix composites were investigated in terms of their longitudinal flexural strength and modulus, interlaminar shear strength, and by optical and scanning electron microscopic observations. The results were compared with a phenolic matrix composite counterpart prepared without xGnP. The flexural properties and interlaminar shear strength of the xGnP-coated carbon fiber/phenolic matrix composites were found to be higher than those of the uncoated composite. The flexural and interlaminar shear strengths were affected by the particle size of the xGnP, while the particle size had no significant effect on the flexural modulus. It seems that the interfacial contacts between the xGnP-coated carbon fibers and the phenolic matrix play a role in enhancing the flexural strength as well as the interlaminar shear strength of the composites.

탄소나노튜브로 보강된 탄소섬유복합재의 제조공정과 층간전단강도

김한상 ( Han Sang Kim ) 한국복합재료학회 2011 Composites research Vol.24 No.5

탄소나노튜브가 발견된 이후로, 고분자 수지의 기계적, 전기적 물성을 증대시키는 보강재로서 많은 연구가 수행되어 왔다. 더 나아가, 탄소나뉴튜브를 탄소섬유복합재 (CFRP)의 기지가 되는 수지를 보강시키는 데 이용하는 연구도 최근 활발해지고 있는 추세이다. 단일벽탄소나노튜브가 각각 0.2 %, 0.5 %의 중량비로 에폭시 수지에 먼저 분산, 혼합되었다. 이 혼합액을 CFRP를 제작하는데 주로 쓰이는 방법 중 하나인 진공 수지 충전 공정법 (vacuum assisted resin transfer molding, VARTM)으로 탄소섬유 프리폼에 주입하는 방법과 습식 현장 적층법 (wet lay-up)의 두가지 다른 방법으로 복합재를 제작 하였다. 각각의 제작된 시편에 대하여, 층간전단강도 (interlaminar shear strength, ILSS)를 측정하여, 층간전단강도와 공정의 상관관계, 탄소나노튜브의 보강효과에 대하여 조사했다. 탄소나노튜브/에폭시 복합재의 경우 기계적 물성의 향상을 가져왔으나 이를 기지재로 사용한 탄소섬유복합재의 층간전단강도는 특히 VARTM 공정의 경우, 탄소나노튜브의 첨가에 따른 수지의 점도 증가로 인한 공정상의 문제로 기대만큼의 물성향상을 가져오지는 못한 것을 확인하였다. Carbon nanotubes (CNTs) have been widely investigated as reinforcements of CNT/polymer nanocomposites to enhance mechanical and electrical properties of polymer matrices since their discovery in the early 90`s. Furthermore, the number of studies about incorporating CNTs into carbon fiber reinforced plastics (CFRP) to reinforce their polymer matrices is increasing recently. In this study, single-walled carbon nanotubes (SWNT) were dispersed in epoxy with 0.2 wt.% and 0.5 wt.%. Then, the SWNT/epoxy mixtures were processed to carbon fiber composites by a vacuum assisted resin transfer molding (VARTM) and a wet lay up method. The processed composite samples were tested for the interlaminar shear strength (ILSS). The relationship between the interlaminar shear strengths and processing, and the reinforcement mechanism of carbon nanotubes were investigated. CNT/epoxy nanocomposite specimens showed the increased tensile properties. However, the ILSS of carbon fiber composites was not enhanced by reinforcing the matrix with CNTs because of processing issues caused by increased viscosity of the matrix due to addition of CNTs particularly for a VARTM method.

탄소섬유/폴리아마이드 6,6 복합재료의 기계적 물성 향상

송승아,온승윤,박고은,김성수 한국복합재료학회 2017 Composites research Vol.30 No.6

탄소섬유 강화 열가소성 수지 복합재료(Carbon fiber reinforced thermoplastic composites; CFRTPs)의 물성은 다양한 요인들에 영향을 받는다. 그 중에서도 탄소섬유 표면에 Sizing되어 있는 에폭시(Epoxy) 층은 열가소성수지와 상호 작용(Interaction)이 없어 매우 취약한 계면을 형성하며, 열가소성 수지의 높은 용융 점도(Melting viscosity) 는 탄소섬유 다발(Bundle) 사이로 함침(Impregnation)이 어려워 탄소섬유 강화 복합재료 내부에 기공(Void)를 형성한다. 이와 같이 탄소섬유와 열가소성 수지 간의 낮은 계면전단강도(Interfacial shear strength)은 탄소섬유강화열가소성 복합재료(Carbon fiber reinforced thermoplastic composites; CFRTPs)의 기계적 물성을 저하시키는 가장 중요한 요인 중 하나이다. 따라서, 본 연구에서는 열가소성 수지와의 상호작용이 없는 탄소섬유 표면의 에폭시 층을 열풍을 통해 제거하고, 열가소성 수지의 점도를 낮춰 함침도를 향상시키기 위해서 용액형 열가소성 수지를 제조하여 탄소섬유 표면에 Sizing 처리 함으로써 CFRTPs의 물성을 향상시켰다. CFRTPs의 층간전단강도(Interlaminar shear strength; ILSS) 및 굽힘 강도(Flexural strength)를 통해 이를 검증하였으며, 수지의 함침도는 기공률(Void content) 의 계산을 통해 분석하였다. Mechanical properties of carbon fiber reinforced thermoplastic composites (CFRTPs) are affected by various factors. One of the them are poor compatibility of the epoxy sizing layer on the carbon fiber surface with thermoplastic matrix, which causes the inferior interfacial strength between fibers and matrix. In addition, the high molten-viscosity of thermoplastics attributes to the poor impregnation state. Consequently, many voids in the composite materials were generated, which leads to poor mechanical properties of the thermoplastic composites. In this study, the epoxy sizing on the carbon fiber surface was removed and the polyamide 6,6 solution was coated on the de-sized carbon fiber surface to improve the impregnation state and mechanical properties. Interlaminar shear strength (ILSS) of CFRPTs was estimated by implementing short beam shear tests. In addition, flexural strength was measured and the impregnation state of the composites was evaluated by calculating void content.

Carbonfiber-Polymer Film 복합소재의 계면강도에 관한 연구

엄찬혁(Chanhyeok Um),이명헌(Myeongheon Lee),곽성복(Sungbok Kwak),한인수(Insoo Han),고윤기(Younki Ko),이현욱(Hyunwook Lee),이평찬(Pyeong-Chan Lee),하진욱(Jin Uk Ha) 한국자동차공학회 2019 한국 자동차공학회논문집 Vol.27 No.6

In this paper, interlaminar shear strength(ILSS) and single-lap shear tests were conducted on thermoplastic resin films and fiber-impregnated composites under various manufacturing pressure conditions. The test results were then compared and analyzed. The results showed increasing interlaminar shear strength until the manufacturing pressure condition of 3 MPa, but the strength started to decrease from the manufacturing pressure condition of 5 MPa. In the case of high elongation resins like polypropylene, the interfacial shear test showed less accuracy than the ILSS test because there was no interfacial fracture due to inelastic deformation. Similar to the result of the single-lap shear test, the interfacial shear strength tended to decrease at 5 MPa in the ILSS test. The fracture mechanism was found to be a cohesive failure mode.

Improved Interlaminar Shear Behaviour of a New Hybrid Kevlar/Cocos Nucifera Sheath Composites with Graphene Nanoplatelets Modified Epoxy Matrix

J. Naveen,M. Jawaid,E. S. Zainudin,Mohamed T. H. Sultan,R. Yahaya 한국섬유공학회 2019 Fibers and polymers Vol.20 No.8

This research investigated the effect of hybridizing Kevlar/cocos nucifera sheath and the effect of adding differentwt.% of Graphene nanoplatelets (GNP) on the interlaminar shear behaviour of laminated composites. Initially, different wt.% (0,0.25, 0.50, and 0.75) of GNP’s were mixed with epoxy resin through Ultrasonic-sonication. Then the laminated compositeswere fabricated by hand lay-up method followed by hot pressing. The weight ratio of Kevlar (K) and cocous nucifera sheath(CS) are 100/0 (S1), 75/25(S2), 50/50 (S3), 25/75(S4), and 0/100(S5). Interlaminar shear strengths (ILSS) of differentlaminates were evaluated using a short beam shear test. The results revealed that hybrid composites S2 (75/25) possess higherILSS than other laminates in the absence of GNP. Addition of GNP at 0.25 wt.% exhibited higher ILSS in all the laminates(S1 to S5) due to the improved interfacial properties. Further addition of GNP (0.50, and 0.75 wt.%) has declined the ILSS ofthe laminated composites due to aggregation and overlapping of GNP. XRD analysis reveals that at 0.25 wt.% of GNP, all thehybrid composites exhibited higher crystallinity index. Statistical analysis of the results has been performed using one way-ANOVA (Analysis of variance) and it shows that there is a statistically significant difference between the obtainedinterlaminar shear strength of the laminated composites.

Ozonization of single-walled carbon nanotubes on fracture toughness and interlaminar shear strength of carbon fiber-reinforced epoxy composites

박상진,박수진 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

In this work, single-walled carbon nanotubes (SWCNTs) surface was successfully modified using the ozone treatment for use as the reinforcement for multi-scale composites. We focused on the fracture toughness, crack resistance, dispersion and interfacial adhesion synergistic effects of ozone-treated SWCNTs (O-SWCNTs) in epoxy matrix and carbon fibers, mechanical properties of the prepared composites were investigated according to weight ratio of O-SWCNTs. The mechanical properties were calculated by the critical stress intensity factor (KIC), critical strain energy release rate (GIC) and interlaminar shear strength (ILSS). The morphology was observed by scanning electron microscope (SEM) and field emission transmission electron microscopy (FE-TEM). Ozone treatment, an environmentally friendly and simple method, suggests a way to improve the mechanical properties of multi-scale composites and modify the surface properties of O-SWCNTs.