Multiscale modeling of PEEK using reactive molecular dynamics modeling and micromechanics

Pisani, William A.; Radue, Matthew S.; Chinkanjanarot, Sorayot; Bednarcyk, Brett A.; Pineda, Evan J.; Waters, Kevin; Pandey, Ravindra; King, Julia A.; Odegard, Gregory M.

doi:10.1016/j.polymer.2018.12.052

Cited by 51 publications

(66 citation statements)

References 28 publications

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“…Few atomistic studies exist on PEEK, which are mostly focused on its structural [26,27] and mechanical properties [28,29], but not on its tribological performance. In this open field, we will investigate what insights MD can provide into friction at the molecular scale, and especially on the shear strength of adhesive junctions.…”

Section: Introductionmentioning

confidence: 99%

Multiscale Friction Simulation of Dry Polymer Contacts: Reaching Experimental Length Scales by Coupling Molecular Dynamics and Contact Mechanics

et al. 2021

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This work elucidates friction in Poly-Ether-Ether-Ketone (PEEK) sliding contacts through multiscale simulations. At the nanoscale, non-reactive classical molecular dynamics (MD) simulations of dry and water-lubricated amorphous PEEK-PEEK interfaces are performed. During a short running-in phase, we observe structural transformations at the sliding interface that result in flattening of the initial nanotopographies accompanied by strong polymer chain alignment in the shearing direction. The MD simulations also reveal a linear pressure -shear stress dependence and large adhesive friction in dry conditions. This dependence, summarized in a nanoscale friction law, is of central importance for our multiscale approach, since it forms a link between MD and elastoplastic contact mechanics calculations. An integration of the nanoscale friction law over the real area of contact yields a macroscopic friction coefficient that allows for a meaningful comparison with measurements from macroscopic tribometer experiments. Severe normal loading conditions result in significant wear and high experimental friction coefficients µ≈0.5-0.7, which are in good agreement with the calculated values from the multiscale approach in dry conditions. For milder experimental loads, our multiscale model suggests that lower friction states with µ≈0.2 originate in the presence of physisorbed molecules (e.g., water), which significantly reduce interfacial adhesion.

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Section: Introductionmentioning

confidence: 99%

Multiscale Friction Simulation of Dry Polymer Contacts: Reaching Experimental Length Scales by Coupling Molecular Dynamics and Contact Mechanics

et al. 2021

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“…Here, we consider Poly-Ether-Ether-Ketone (PEEK), a semicrystalline thermoplastic with outstanding mechanical properties, thermal stability, and chemical resistance, thus constituting an excellent material for bearing and sealing applications. Few MD studies exist for this material, mostly focused on its structural [21,22] and mechanical properties [23,24], but not on its tribological performance. In this open field, we will investigate what insights MD can provide into friction at the molecular scale, and especially on the shear strength of adhesive junctions.…”

Section: Introductionmentioning

confidence: 99%

Multiscale Friction Simulation of Dry Polymer Contacts: Reaching Experimental Length Scales by Coupling Molecular Dynamics and Contact Mechanics

Savio

Hamann

Romero

et al. 2021

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This work elucidates friction in Poly-Ether-Ether-Ketone (PEEK) sliding contacts through multiscale simulations. At the nanoscale, non-reactive classical molecular dynamics (MD) simulations of dry and water-lubricated amorphous PEEK-PEEK interfaces are performed. During a short running-in phase, we observe structural transformations at the sliding interface that result in flattening of the initial nanotopographies accompanied by strong polymer chain alignment in the shearing direction. Our MD simulations reveal a linear pressure-dependence of the shear stress τMD (P,σH2o) [MPa]=0.18P + 50.5 - 1.25σH2o, where σH2o [nm-2] is the surface number density of adsorbed water molecules. This constitutive law is of central importance for our multiscale approach, since it forms a link between MD and elastoplastic contact mechanics calculations. An integration of τMD (P,σH2o) over the real area of contact yields a macroscopic friction coefficient μmacro (σH2o) that allows for a meaningful comparison with friction coefficients μexp≈0.5-0.7 which are in good agreement with the calculated dry friction coefficients μmacro(σH2o=0).For milder experimental loads, our multiscale model suggests that the lower friction states with μexp≈0.2 originate in the presence of physisorbed molecules (e.g. water), which significantly reduce interfacial adhesion.

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“…Therefore, the purpose of this study is to compare the entropy increase at failure with different combined stress states and to investigate whether or not the material fails at a constant entropy increase in all simulations. In addition to reproducing the damage mechanism at the molecular level, molecular simulations allow us to consider thermodynamic parameters, such as internal energy [ 19 , 20 ], which are difficult to obtain experimentally, in addition to temperature [ 21 , 22 ], interface energy [ 23 , 24 ], and mechanical properties [ 25 , 26 , 27 ]. At the same time, we propose a method for calculating entropy, which has recently been used in a discussion of molecular dynamics simulations [ 28 , 29 , 30 , 31 , 32 , 33 ].…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulation for Evaluating Fracture Entropy of a Polymer Material under Various Combined Stress States

et al. 2021

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Herein, the stress-state dependence of fracture entropy for a polyamide 6 material is investigated through molecular dynamics simulations. Although previous research suggests that a constant entropy increase can be universally applied for the definition of material fracture, the dependence of stress triaxiality has not yet been discussed. In this study, entropy values are evaluated by molecular dynamics simulations with varied combined stress states. The calculation is implemented using the 570,000 all-atom model. Similar entropy values are obtained independently of stress triaxiality. This study also reveals the relationship between material damage, which is correlated with void size, and the entropy value.

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Multiscale modeling of PEEK using reactive molecular dynamics modeling and micromechanics

Cited by 51 publications

References 28 publications

Multiscale Friction Simulation of Dry Polymer Contacts: Reaching Experimental Length Scales by Coupling Molecular Dynamics and Contact Mechanics

Multiscale Friction Simulation of Dry Polymer Contacts: Reaching Experimental Length Scales by Coupling Molecular Dynamics and Contact Mechanics

Multiscale Friction Simulation of Dry Polymer Contacts: Reaching Experimental Length Scales by Coupling Molecular Dynamics and Contact Mechanics

Molecular Dynamics Simulation for Evaluating Fracture Entropy of a Polymer Material under Various Combined Stress States

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