DOI: 10.5281/zenodo.7685164
title: Extending a generic and fast coarse-grained molecular dynamics model to examine the mechanical behavior of grafted polymer nanocomposites: data set

description: Abstract:<br> from [1] Polymer nanocomposites are an important class of materials for engineering applications due to their high versatility and good mechanical properties combined with low density. By directly attaching the polymer chains to the nanofillers, the so-called grafting, a better load transfer between matrix and filler is achieved, and, in addition, a better dispersion of the fillers is obtained. Both result in enhanced mechanical properties. Since experimental investigations on the nanoscale are extremely challenging, complementary numerical studies are needed to unravel the mechanical behavior of polymer nanocomposites. To this end, molecular dynamics is ideally suited since it captures the microstructure, but is also numerically expensive. Therefore, this contribution presents a fast coarse-grained molecular dynamics model for the investigation of the mechanical behavior of grafted polymer nanocomposites. For this purpose, we extend an existing model by grafting bonds, which allows us to compare the effect of untreated and grafted fillers directly. In particular, we investigate the influence of filler content, grafting degree, and filler size on the stiffness and strength of the polymer (grafted) nanocomposites. We conclude that the grafting bonds have little effect on the stiffness, while the strength is significantly improved compared to the untreated fillers, which is in agreement with the literature. The presented molecular dynamics model for polymer grafted nanocomposites provides the basis for further investigations, particularly of the crucial matrix-filler interphase. In addition, this contribution translates molecular dynamics insights into mechanical properties, which bridges the gap to the engineering scale and thus represents a step towards exploiting the full potential of polymer (grafted) nanocomposites. <strong>Contact:</strong> Maximilian Ries<br> Institute of Applied Mechanics<br> Friedrich-Alexander-Universität Erlangen-Nürnberg<br> Egerlandstr. 5<br> 91058 Erlangen <strong>Software:</strong> All MD simulations were performed with LAMMPS [2,3], version: 29 Oct 2020 / 20201029 Compiled with<br> Compiler: GNU C++ 4.8.5 20150623 (Red Hat 4.8.5-39) with OpenMP not enabled<br> C++ standard: C++11 Active compile time flags:<br> -DLAMMPS_GZIP<br> -DLAMMPS_SMALLBIG Installed packages:<br> CLASS2, KSPACE, MANYBODY, MC, MOLECULE, MPIIO, OPT, VORONOI, USER-INTEL, USER-MISC, USER-MOLFILE, USER-NETCD Polymer and polymer composite samples generated with self-avoiding random-walk algorithm [4] Post-processing Matlab R2019b <strong>License:</strong> Creative Commons Attribution 4.0 International <strong>Context:</strong> Data set supplementing journal paper: [1] M. Ries, S. Reber, P. Steinmann, & S. Pfaller, “Extending a generic and fast coarse-grained molecular dynamics model to examine the mechanical behavior of grafted polymer nanocomposites,” <em>Forces in Mechanics</em>, vol. 12, p. 100 207, <strong>2023</strong>. <strong>Content:</strong> structure of data set: 04_Equilibration<br> folders containing the sample equilibration used in the presented parameter study 01_filler_content<br> variation of filler content 02_grafting_density<br> variation of grafting density 03_grafting_potential<br> variation of grafting potential 04_filler_size<br> variation of filler size 05_reference<br> reference samples without grafting 05_UT<br> folders containing the uniaxial tension simulations used in the presented parameter study 01_filler_content<br> variation of filler content 02_grafting_density<br> variation of grafting density 03_grafting_potential<br> variation of grafting potential 04_filler_size<br> variation of filler size 05_reference<br> reference samples without grafting Each simulation directory contains: lammps input file (*.in) of the specific simulation data file (*.data) containing the initial sample configuration input.prm: input parameters of the specific simulation (read by the input file) meta.info: meta data of the specific simulation run LAMMPS_out:<br> simulation results (lammps thermo_out) in tabulated form, an overview of columns is given below thermo_out.Dat: raw output thermo_out_SG.Dat: smoothed output (Savitzky-Golay filter) thermo_out_STD.Dat: standard deviation of raw output Output quantities (columns of *.Dat files):<br> Please note that the normalized Lennard-Jones unit set is used, so all quantities are normalized to fundamental mass, length, energy, time and the Boltzmann constant. Thus all entries are unitless [1]. Step: time step Time: time TotEng: total energy PotEng: potential energy KinEng: kinetic energy E_pair: pair energy E_bond: bond energy E_angle: angle energy E_dihed: dihedral energy Temp: temperature Press: hydrostatic pressure Pxx: xx component of pressure tensor Pyy: yy component of pressure tensor Pzz: zz component of pressure tensor Pxy: xy component of pressure tensor Pxz: xz component of pressure tensor Pyz: yz component of pressure tensor Volume: volume of simulation box Lx: box length in x direction Ly: box length in y direction Lz: box length in z direction Density: density c_RG: radius of gyration scalar c_RG[1]: squared radius of gyration tensor (xx component) c_RG[2]: squared radius of gyration tensor (yy component) c_RG[3]: squared radius of gyration tensor (zz component) c_RG[4]: squared radius of gyration tensor (xy component) c_RG[5]: squared radius of gyration tensor (xz component) c_RG[6]: squared radius of gyration tensor (yz component) c_bondave[1]: bond energy averaged over all atoms c_bondave[2]: bond distance averaged over all atoms c_bondave[3]: squared bond distance averaged over all atoms c_angleave[1]: angle energy averaged over all atoms c_angleave[2]: angle averaged over all atoms degree c_angleave[3]: cosine of angle c_angleave[4]: squared cosine of angle c_MSD[1]: mean squared displacement x-direction c_MSD[2]: mean squared displacement y-direction c_MSD[3]: mean squared displacement z-direction c_MSD[4]: total mean squared displacement c_COM[1]: x coordinate of center of mass c_COM[2]: y coordinate of center of mass c_COM[3]: z coordinate of center of mass v_strain_xx: xx component of engineering strain tensor v_strain_yy: yy component of engineering strain tensor v_strain_zz: zz component of engineering strain tensor v_vMisesequivstress: von Mises equivalent stress v_Cauchy_xx: xx component of stress tensor v_Cauchy_yy: yy component of stress tensor v_Cauchy_zz: zz component of stress tensor v_Cauchy_xy: xy component of stress tensor v_Cauchy_xz: xz component of stress tensor v_Cauchy_yz: yz component of stress tensor v_strain_xy: xy component of engineering strain tensor v_strain_xz: xz component of engineering strain tensor v_strain_yz: yz component of engineering strain tensor <strong>References</strong>: [1] M. Ries et al., “Extending a generic and fast coarse-grained molecular dynamics model to examine the mechanical behavior of grafted polymer nanocomposites,” <em>Forces in Mechanics</em>, vol. 12, p. 100 207, <strong>2023</strong>. [2] S. Plimpton, “Fast parallel algorithms for short-range molecular dynamics,” <em>Journal of computational physics</em>, <strong>1995</strong>, 117, 1-19. [3] A. P. Thompson et al., “LAMMPS - a flexible simulation tool for particle-based materials modeling at the atomic, meso, and continuum scales,” <em>Computer Physics Communications</em>, vol. 271, p. 108171, <strong>2022</strong>. [4] M. Ries, V. Dötschel, J. Seibert, S. Pfaller. “A self-avoiding random walk algorithm (SARW) for generic thermoplastic polymers and nanocomposites”, <em>Zenodo</em>, 2022. https://doi.org/10.5281/zenodo.6245699
description: Sebastian Pfaller is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - 396414850 (Individual Research Grant 'Identifikation von Interphaseneigenschaften in Nanokompositen'). Maximilian Ries, Paul Steinmann, and Sebastian Pfaller are funded by the DFG - 377472739 (Research Training Group GRK 2423 'Fracture across Scales - FRASCAL').