Growth, microstructure, and failure of crazes in glassy polymers

Abstract

We report on an extensive study of craze formation in glassy polymers. Molecular dynamics simulations of a coarse-grained bead-spring model were employed to investigate the molecular level processes during craze nucleation, widening, and breakdown for a wide range of temperature, polymer chain length $N$, entanglement length $N_e$ and strength of adhesive interactions between polymer chains. Craze widening proceeds via a fibril-drawing process at constant drawing stress. The extension ratio is determined by the entanglement length, and the characteristic length of stretched chain segments in the polymer craze is $N_e/3$. In the craze, tension is mostly carried by the covalent backbone bonds, and the force distribution develops an exponential tail at large tensile forces. The failure mode of crazes changes from disentanglement to scission for $N/N_e\sim 10$, and breakdown through scission is governed by large stress fluctuations. The simulations also reveal inconsistencies with previous theoretical models of craze widening that were based on continuum level hydrodynamics.

References in corpus (5)

• What is the Entanglement Length in a Polymer Melt ?
• Cracks and Crazes: On calculating the macroscopic fracture energy of glassy polymers from molecular simulations
• Yield conditions for deformation of amorphous polymer glasses
• Local Reorientation Dynamics of Semiflexible Polymers in the Melt
• Jamming under tension in polymer crazes

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