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열가소성 플라스틱의 기계적 거동 예측을 위한 Coarse-grained 모델 구축
유태우(Taewoo Yoo),김병조(Byungjo Kim),정인균(Ingyun Chung),박형범(Hyungbum Park),조맹효(Maenghyo Cho) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
Coarse-grained (CG) modeling has emerged as a useful tool in molecular dynamic simulation, which can maintain the molecular details and also reflect mesoscopic properties with less computational efforts and time. In this study, the mechanical properties of Polypropylene polymer such as young’s modulus, ultimate tensile strength and hysteresis are investigated with CG model. CG potential is designed based on the strain energy conservation between CG model and all-atom model. Comparing stress-strain curves of two models, the present method shows that CG model can capture mechanical properties of all-atom model with high accuracy. Hysteresis is successfully observed in repeated loading and unloading simulation. Furthermore, the effects of cyclic loading on the structural variations are examined. The application of CG potential in the polymer system with a longer chain length is conducted. The present CG potential will be able to cover a wide range of time and length scale in the polymer system.
계면 분리와 고분자 기지 데미지 현상을 고려한 CNT/고분자 나노복합재의 기계적·전기적 거동에 대한 멀티스케일 해석
이원석(Wonseok Lee),백경민(Kyungmin Baek),정인균(Ingyun Chung),임선영(Sunyoung Im),조맹효(Maenghyo Cho) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
In this study, a multiscale analysis is conducted to investigate the electrical and mechanical behavior of carbon nanotube (CNT)-polymer nanocomposites considering matrix damage and interfacial debonding with computational micromechanics. CNT-polymer nanocomposites exhibit piezoresistive response which is the effect that the resistivity is changed when subjected to applied deformation. Mechanical and electrical properties are degraded by polymer matrix damage and interfacial debonding phenomenon which occur inevitably when nanocomposites are applied deformation. In order to describe polymer matrix damage representing void nucleation, disentanglement and eventual breakage of polymer chain, we use Christensen’s failure criteria and phenomenological damage law. Interfacial debonding is described by the electromechanical cohesive zone where the interface between CNT and polymer is separated. We identify that the the stress distribution between the debonding model and the perfectly bonded model is clearly different. This difference causes the opposite matrix damage behavior, which in turn affect the changes of electrical and mechanical properties.