A nanoscale study of size scale, strain rate, temperature, and stress state effects on damage and fracture of polyethylene

AL Bowman and S Mun and BD Huddleston and SR Gwaltney and MI Baskes and MF Horstemeyer, MECHANICS OF MATERIALS, 161, 104008 (2021).

DOI: 10.1016/j.mechmat.2021.104008

The mechanical properties and damage behavior of amorphous polyethylene are investigated using Molecular Dynamics (MD) simulations. The influence of time, temperature, size scale, and stress state are extensively studied to gather insights into the complex nature of glassy polymers and the related damage process of void formation during dynamic loading conditions. The Modified Embedded Atom Method (MEAM) is employed to model interatomic interactions, balancing computational efficiency with a superior description of free surfaces and void formation to provide a detailed analysis of the progression of damage in the form of nucleation, growth, and coalescence of voids. The MD simulations capture the evolution of the number and size of voids and are shown to correlate to specific regimes of the stress-strain response. Particular attention is given to the quantification of void coalescence and the influence coalescence has on the growth and nucleation rates of voids. A nanoscale parameter, the critical Inter-void Ligament Distance (ILD), is defined for the initiation of void coalescence, and is found to be about 0.75 void diameters resulting in the enhancement of void growth and the restriction of void nucleation once the critical ILD is achieved. This study provides important insight into the damage progression of glassy polymers that cannot be defined through current experimental techniques.

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