비균일 진주층 모사 다층형 복합재료의 내충격성에 관한 수치해석

이태희,고권환,홍정욱 한국전산구조공학회 2022 한국전산구조공학회논문집 Vol.35 No.4

Significant efforts have been devoted to developing high-performance composite materials by emulating the structure of biological creatures with superior mechanical characteristics. Nacre has been one of the most sought-after natural structures due to its exceptional fracture toughness compared with the constituent materials. However, the effect of manipulating the nacre-like geometry on the impact performance has not been fully investigated thus far. In this study, composites of randomly manipulated nacreous geometry are numerically developed and the impact performance is analyzed. We develop an algorithm by which the planar area of platelets in the nacre-like design is randomly resized. Thereafter, the numerical models of nonuniform nacre-patterned multi-layer structures are developed and the drop-weight impact simulation is performed. The impact behaviors of the model are evaluated by using the ratio of absorbed energy, the von Mises stress distribution, and the impact force-time curve. Therefore, the effect of the geometric irregularity on the nacre-patterned design is elucidated. This insight can be efficiently utilized in establishing the optimum design of the nacre-patterned structure. 우수한 역학적 성능을 가진 생물체의 구조를 모방하여 고성능의 복합재료를 개발하려는 노력이 최근 활발히 이뤄지고 있다. 진주층 구조는 구성재료 대비 월등히 높은 파괴인성을 지닌다는 점에서 촉망받는 자연 모사 구조 중 하나이다. 하지만, 진주층 모사 구조의 형상이 변형될 때 구조의 충격성능이 어떻게 달라지는지에 관한 연구는 아직 충분히 진행되지 않았다. 본 연구에서는 무작위로 변형된 진주층 모사 복합재의 수치모델을 개발하고 충격성능을 분석하였다. 먼저, 균일한 진주층 모사 패턴에서 플레이트 판의 평면 크기를 무작위로 변형하는 알고리즘을 개발하고 이를 활용하여 불균일한 진주층 패턴 모사 구조를 모델링하였다. 그 후, 낙하충격 시뮬레이션을 수행하고 해당 모델의 충격거동을 에너지 흡수율과 본 미세스 응력 분포, 충격력-시간 그래프를 활용하여 평가하였다. 수치해석결과를 바탕으로, 충돌 범위 주변 플레이트 판의 기하학적 형상이 불균일할수록 진주층 모사 구조의 내충격성이 저하됨을 입증하였다. 이러한 진주층 모사 형상에 대한 심층적인 이해는 진주층 모사 구조의 최적설계를 수립하는 데 효율적으로 활용될 수 있을 것으로 기대된다.

Effects of asperities and organic-inorganic interactions on the strength of nacre-mimetic composites

Lee, Yoonjoo,Kim, Bo-Yeon,Shin, Dong-Geun,Kim, Soo-Ryong,Kwon, Woo-Teck,Kim, Younghee Elsevier 2017 Materials Science and Engineering C Vol.71 No.-

<P>Nacre is a natural organic-inorganic hybrid composite, whose hierarchical structure has a complex influence on its high strength. Many structural features have been discovered, which influence the mechanical properties of nacre, and the authors have a particular interest in the role of the asperities and organic-inorganic interactions. In this study, a composite was prepared which mimics the asperity structure using clay minerals. Organic-inorganic bonding was induced with silane treatment. Both factors increased the yield strength of the composites; however, different deformation behavior was exhibited. It was found that asperities improved the strength of the composite, and that composition influences the stiffness of the composite. The organic-inorganic interaction between the resin and the other components of the composite reduced the deformation of the composite and consequently improved strength. (C) 2016 Published by Elsevier B.V.</P>

Nacre-inspired composite prepared by rolling method I: Effect of particle orientation on deformation behavior

Lee, Yoonjoo,Shin, Dong-Geun,Jeong, Un-Seung,Kim, Soo-Ryong,Kwon, Woo-Teck,Kim, Younghee Elsevier 2017 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.182 No.-

<P><B>Abstract</B></P> <P>In this study, we prepared a perfectly ordered nacre-mimetic composite from plate-like alumina particles and epoxy resin using a rolling method. A specific feature of this method is that it progressively aligns the component particles along a single direction regardless of the product thickness at resin contents as low as 25wt%. The obtained composite exhibited a strength as high as 200MPa during bending. However, to examine the mechanical properties of artificial nacre, various factors such as the types of initial components and their particle sizes, contents, and orientation degrees must be considered. Hence, this study consists of two parts. The present work (which constitutes the first part) is focused on the orientation effect produced by the plate-like particles and deformation behavior of the composites observed at different orientation degrees. It was found that the obtained composite material with perfectly ordered particles exhibited pull-out behavior similar to that of natural nacre (including the crack propagation route). Further, the fracture toughness of the composite, which was higher than that of alumina, was also affected by its orientation degree.</P>

전복껍질 메소절편 기반 복합소재 합판 제작 및 이를 이용한 하이브리드 판재의 방탄특성

김정우,강대원,백종규,육영기,박정호,신상모,Kim, Jeoung Woo,Kang, Dae Won,Paik, Jong Gyu,Youk, Youngki,Park, Jeong Ho,Shin, Sang-Mo 한국재료학회 2019 한국재료학회지 Vol.29 No.1

Nacre of abalone shell features a "brick-and-mortar" microstructure, in which micro-plates of calcium carbonate are bonded by nanometers-thick layers of chitin and proteins. Due to the microstructure and its unique toughening mechanisms, nacre possesses an excellent combination of specific strength, stiffness and toughness. This study deals with the possibility of using nacre fragments obtained from abalone shell for making a bulletproof armor system. A composite plate laminated with abalone shell fragments is made and compression and bend tests are carried out. In addition, a bulletproof test is performed with hybrid armor systems which are composed of an alumina plate, a composite plate, and aramid woven fabric to verify the ballistic performance of nacre. The compressive strength of the composite plate is around 258.3 MPa. The bend strength and modulus of the composite plate decrease according to the plate thickness and are about 149.2 MPa and 50.3 GPa, respectively, for a 4.85 mm thick plate. The hybrid armor system with a planar density of $45.2kg/m^2$, which is composed of an 8 mm thick alumina plate, a 2.4 mm thick composite plate, and 18 layers of aramid woven fabric, satisfy the NIJ Standard 0101.06 : 2008 Armor Type IV. These results show that a composite plate laminated with abalone shell fragments can be used for a bulletproof armor system as an interlayer between ceramic and fabric to decrease the armor system's weight.

Improving mechanical properties of bioinspired Clay-Cellulose Nanofibers composites

허재은,장다슬,배은실,심봉섭 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

In nature, nacre has the hierarchical brick-and-mortar structures and precise inorganic-organic interfaces, which enable it to achieve remarkably high fracture toughness and tensile strength. Because of these properties, nacre-mimetics hold great potential as mechanical high-performance and functional materials. Previously, we have fabricated nacre-like nanocomposites via vacuum filtration of montmorillonite (MMT) and cellulose nanofibers(CNFs) mixtures. Although the composites exhibited higher strength and toughness than pure MMT and CNFs, we tried to improve the mechanical properties further y by additional post treatmentsive work. In this study, adding polymers and cross-linking were introduced to improve the mechanical propertiesy of the composites. The resulting materials were analyzed by a Scanning electron microscopy(SEM), an X-ray diffraction(XRD), and a tensile tester. We compare the resulting mechanical properties with the previous results.

An extended analytic model for the elastic properties of platelet-staggered composites and its application to 3D printed structures

Kim, Youngsoo,Kim, Yongtae,Lee, Tae-Ik,Kim, Taek-Soo,Ryu, Seunghwa Elsevier 2018 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.189 No.-

<P><B>Abstract</B></P> <P>The load transfer mechanism in the unique staggered platelet structure of nacre has been intensively analyzed, and its structural features have been mimicked by various manufacturing methods such as 3D printing. However, due to the limited applicability of most analytical models and the limitations of 3D printers, it remains difficult to quantitatively predict and design the properties of nacre-inspired synthetic structures. In this study, we improve the analytic models to predict the effective elastic properties of various staggered platelet structures for a wide range of constituent materials’ elastic moduli and geometric parameters by carefully accounting for the volume average of elastic properties. We also systematically investigate the effect of the printing orientation and width of the composite structure fabricated by a 3D printer. We show that our improved analytic model accurately predicts the properties of a 3D printed composite when the manufacturing-condition-dependent material properties are used as input. Our study reveals the origin of discrepancy between theory and 3D printed structures and enables a rational design of nacre-inspired structures.</P>

Fabrication of a Strong Artificial Nacre Based on Tannic Acid- Functionalized Graphene Oxide and Poly(vinyl alcohol) Through Their Multidentate Hydrogen Bonding

권유빈,이상룡,서태훈,김영관 한국고분자학회 2022 Macromolecular Research Vol.30 No.4

A strong graphene oxide (GO)-based artificial nacre is developed by using a simple and efficient interfacial chemistry. GO is simultaneously reduced and functionalized with tannic acid (TA) and the resulting TA-reduced GO (TA-RGO) exhibits a high aqueous dispersibility owing to abundant phenol groups. TA-RGO sheets are incorporated with poly(vinyl alcohol) (PVA) and then assembled into an artificial nacre-like structure by vacuum-assisted filtration to induce the formation of multidentate interfacial hydrogen bonding between TA-RGO and PVA. Based on the multidentate hydrogen bonding, the resulting TA-RGO/ PVA (1 wt%) composite film presented an overall and efficient reinforcement of tensile strength (186.1 ± 12.8 MPa), modulus (15.2 ± 1.2 GPa) and toughness (1546 ± 248 kJ/m3) compared to those of GO (83.3 ± 5.4 MPa, 8.9 ± 0.4 GPa and 1434 ± 152 kJ/m3) and TA-RGO (87.6 ± 10.6 MPa, 13.8 ± 1.4 GPa and 306 ± 51 kJ/m3), respectively. The present study demonstrates the rational design of interfacial interaction can greatly improve the performance of a structural composite material.

Nacre-Inspired Organic/Inorganic Composites via Layer-by-Layer of ZrHP Nanoplatelets and Polyurethane Matrix

강민수,성민철,김진웅 한국공업화학회 2023 한국공업화학회 연구논문 초록집 Vol.2023 No.0

1930년대 조선총독부의 공업 정책과 나전 기술의 변용

강연경 국립무형유산원 2018 무형유산 Vol.- No.5

Mother-of-pearls have received attention as a key craft of Korea. They are being activelyproduced and passed down. Techniques of mother-of-pearls encountered changes in manyways in the modern period. Mother-of-pearls was a luxury item of the upper class in the Koreantraditional society. It turned into just a product by the collapse of the feudal manufacture systemand the change in the production and consumption trends. A conversion to the mass productionsystem was required in this process and the production method of mother-of-pearls was alsochanged. It is confirmed in not only change in introduction of a fret saw and design, but also useof lacquer and making nacre. However, the other changes then that fret saw have not been givenattention until now. Change of technique of mother-of-pearls are related to the industrial policy of the JapaneseGovernment General of Korea. In particular, there were a variety of discussions to improve motherof-pearls as a product consumed in Joseon and Japan, and also as a promising export item in the1930’s. The Central Research Laboratory in Colonial Korea proceeded various tests to increase theproduction of lacquer in Joseon. The improvement test of mother-of-pearls was proceeded as aapplied research. The Product Investigation Research established in the Japanese GovernmentGeneral of Korea attempted improved methods through discussions with Japanese industrialistsrelated to production of mother-of-pearls. The improvement methods were reflected andattempted in a policy. The result of it is recorded in the designation reports of master craftsmen,who worked in Japanese colonial era and were designated as intangible cultural heritageNajeonjang after the independence. These improvement methods suggested by the Japanese Government General of Koreawas limited to improve productivity of mother-of-pearls and developed as an export item. Theimprovement of technique of mother-of-pearls focused on developing production efficiency contributed to the popularization of lacquerware inlaid with mother-of-pearls. However,improvements that were limited to production caused harm to the essence of mother-of-pearls. Now is the time to seek its own way, rather than the way developed by the Japanese GovernmentGeneral of Korea. This study is an attempt to go back to the changes of technique of mother-ofpearlin the Modern period and look at the improvement process through industrial policy of theJapanese Government General of Korea. 나전은 예로부터 한국의 대표적인 공예 중 하나로 주목받아 왔으며, 제작활동과 전승 또한 활발히 이뤄지고 있다. 근대에 나전 기술은 여러 방면에서 변화를 맞게 된다. 전통사회에서 상류층의 사치품이었던 나전은 봉건적 경공장 체제가 붕괴되고 제작과 소비의 경향이 변화하면서 상품으로 변모한다. 이 과정에서 대량생산 체제로의 전환이 요구되었으며, 제작방식에 있어서도 변화를 보인다. 선행 연구에서 파악되고 있는 실톱의 도입과 의장의 변화뿐만 아니라 칠의 사용, 섭패 방식 등 다양하게 확인된다. 그러나 실톱을 제외하고그 외의 변화에 대해서는 지금까지 주목된 바가 없었다. 근대에 나전 기술의 변화는 일제강점기 조선총독부의 공업 정책과 연관을 지닌다. 특히 나전칠기의 생산과 수출이 활발했던 1930년대에 나전칠기를 조선과 일본에서 소비되는 상품에서 나아가 유망한 수출품으로서 개량하기 위한 논의가 다양하게 이루어졌다. 중앙시험소에서는 조선에서의 칠 증산을 위한 채칠시험을 진행했으며, 이의 응용 연구로 나전칠기의 개량시험을 진행하였다. 조선총독부 상공장려관 내에 설치된상품조사연구회에서는 실질적으로 나전 생산과 관련하여 종사하는 일본인 공업가들과의 논의를 통해 개량방안을 꾀하였다. 일제에 의해 논의된 개량 방안은 정책에 반영되어 시도되었으며, 그 흔적은 일제강점기에활동하여 해방 이후 무형문화재 나전장으로 지정된 장인들의 지정보고서에 기록되어 있다. 일제의 이러한 개량은 나전 생산의 효율을 향상시켜 재래공업으로서 수출품으로 발전시키는 데에 한정되어 있었다. 생산 효율의 향상에 초점이 맞춰진 나전 기술의 개량은 해방 이후 이뤄진 나전칠기의 저변화에 기여한 면이 있었다. 그러나 생산에 한정된 개량은 나전 본래의 모습을 해치기도 하는 결과도 발생시켰다. 한국 나전의 정체성을 다시 되찾아 근대의 타율적인 개량이 아닌 우리 스스로의 자율적인 개량 방안의모색이 요구되는 시점에서 본 논문은 근대 나전 기술의 변화를 소급하고 일제의 공업 정책을 통한 나전의개량 과정을 짚어보고자 하는 시도이다.

Bioinspired Cellulose Nanocomposites and Mechanical Properties

문성민,허경아,심봉섭 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0

The brick and mortar structure of nacre has shown remarkable mechanical properties in nature. Inspired by their hierarchically aligned structures between chitin fibers and calcium carbonate platelets, we have fabricated nacre-like nanolayered structures of cellulose nano-fiber (CNF) and montmorillonite (MMT) via vacuum filtration techniques with different CNF/MMT ratio. The molecular structures of CNF-MMT films were observed by scanning electron microscopic and X-ray diffraction. The mechanical strength and modulus of CNF-MMT nano-composite were higher than those of pure CNF and MMT films. Furthermore, the CNF-MMT films have shown fire-retardant properties while containing large amounts of cellulose. Thus, CNF-MMT nanocomposite can be a good candidate for environmental-friendly materials in the wide ranges of industrial application fields.