Multiscale modeling of PEEK using reactive molecular dynamics modeling and micromechanics

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

doi:10.1016/j.polymer.2018.12.052

Evan J Pineda, Ravindra Pandey + Show 7 more

Open Access

https://doi.org/10.1016/j.polymer.2018.12.052

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Abstract

Polyether ether ketone (PEEK) is a high-performance, semi-crystalline thermoplastic that is used in a wide range of engineering applications, including some structural components of aircraft. The design of new PEEK-based composite materials can be greatly facilitated with a precise understanding of the multiscale structure and behavior of semi-crystalline PEEK. Molecular Dynamics (MD) modeling can efficiently predict the response of single-phase polymers at the nanometer length scale, and micromechanics can be used to predict the bulk-level properties of multi-phase materials based on the microstructure. In this study, MD modeling was used to predict the mechanical response of the amorphous and crystalline phases of PEEK. Employing the MD simulation results as input, the hierarchical microstructure of PEEK, which combines these two phases, was modeled using NASA's micromechanics MSGMC (Multi-Scale Generalized Method of Cells) code. The predicted bulk mechanical properties of semi-crystalline PEEK agree well with the scientific literature data, thus validating the multiscale modeling approach. Thus, the proposed multiscale modeling method can be used to accurately and efficiently predict the mechanical response of other micro-structurally complex polymer systems.

Highlights

Polymer matrix composites are increasingly used in place of metals in the aerospace industry due to their comparable mechanical properties and lightweight nature, which increases fuel efficiency and reduces emissions
To effectively simulate semi-crystalline Polyether ether ketone (PEEK) materials, a multi-scale approach can be used in which the amorphous and crystalline phases are modeled separately using molecular dynamics (MD), and micromechanics is subsequently used to obtain the bulk properties of PEEK using repeating unit cells (RUCs) that represent the spatial arrangement of these phases at larger length scales
The objective of this study is to demonstrate that MD modeling and Multi-Scale Generalized Method of Cells (MSGMC) (Ref. 4) can be used together to accurately predict the mechanical properties of semicrystalline PEEK

Summary

Introduction

Polymer matrix composites are increasingly used in place of metals in the aerospace industry due to their comparable mechanical properties and lightweight nature, which increases fuel efficiency and reduces emissions. Talbott et al determined by x-ray scans that the crystalline structure deteriorates significantly (~10 percent drop in crystallinity) when the applied compression loading increases beyond the yield point (Ref. 1). Despite these initial efforts, more research is needed to provide a better understanding of the effect of molecular structure on bulk thermo-mechanical properties of PEEK. To effectively simulate semi-crystalline PEEK materials, a multi-scale approach can be used in which the amorphous and crystalline phases are modeled separately using MD, and micromechanics is subsequently used to obtain the bulk properties of PEEK using repeating unit cells (RUCs) that represent the spatial arrangement of these phases at larger length scales

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Results

Conclusion