Molecular Dynamics Simulation of a Pullout Test on a Carbon Nanotube in a Polymer Matrix
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Molecular Dynamics Simulation of a Pullout Test on a Carbon Nanotube in a Polymer Matrix Guttormur Arnar Ingvason1 and Virginie Rollin1 1
Embry-Riddle Aeronautical University, Aerospace Engineering Department, 600 South Clyde Morris Blvd, Daytona Beach, FL 32114, U.S.A. ABSTRACT Adding single walled carbon nanotubes (SWCNT) to a polymer matrix can improve the delamination properties of the composite. Due to the complexity of polymer molecules and the curing process, few 3-D Molecular Dynamics (MD) simulations of a polymer-SWCNT composite have been run. Our model runs on the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS), with a COMPASS (Condensed phase Optimized Molecular Potential for Atomistic Simulations Studies) potential. This potential includes non-bonded interactions, as well as bonds, angles and dihedrals to create a MD model for a SWCNT and EPON 862/DETDA (Diethyltoluenediamine) polymer matrix. Two simulations were performed in order to test the implementation of the COMPASS parameters. The first one was a tensile test on a SWCNT, leading to a Young’s modulus of 1.4 TPa at 300K. The second one was a pull-out test of a SWCNT from an originally uncured EPON 862/DETDA matrix. INTRODUCTION
Carbon Fiber Reinforced Plastic (CFRP) has been researched and used for many decades but still has the structural drawback of only being resilient in the fiber direction. This can be alleviated using layers with different fiber directions. The thickness strength (perpendicular to the fibers) of the CFRP or any composite material is not nearly as high as in the fiber direction [1]. Crack initiation and growth is a weakness of CFRP. These crack failures often present themselves as delamination at the interface between two layers. In order to improve the strength of CFRP and prevent or delay delamination, Single Walled Carbon Nanotubes (SWCNTs) can be added to the polymer matrix. If a minute delamination occurs in between two layers of composite, the carbon nanotubes (CNTs) act as a barrier and stop the delamination from propagating further between the layers. The CNT bridges the gap in the resin and deflects the crack propagation [1]. This improves the delamination toughness of the composite [2]. The study of CNT/polymer pull out tests is important in understanding how CNTs can assist in delaying or preventing delamination in CFRP. The goal of this research is to implement the Condensed phase Optimized Molecular Potential for Atomistic Simulations Studies (COMPASS) potential parameters in the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) [3]. The potential is then used in two different simulations to test its implementation. The first is a simple tension test on a SWCNT and the second one is a pull out test with a SWCNT and a mix of EPON 862 resin with a DETDA curing agent. A pullout simulation gives information on the interaction between CNT and polymer matrix, and hence the strength of the composite.
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FORCE FIELD The COMPASS force field was chosen for implementation in the MD si
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