Network approach towards understanding the crazing in glassy amorphous polymers

摘要

We have used molecular dynamics to simulate an amorphous glassy polymer withlong chains to study deformation mechanism of crazing and associated voidstatistics. The Van der Waals interactions and the entanglements between chainsconstituting the polymer play a crucial role in crazing. Thus, we havereconstructed two underlying weighted networks, namely, the Van der Waalsnetwork and the Entanglement network from polymer configurations extracted fromthe molecular dynamics simulation. Subsequently, we have performedgraph-theoretic analysis of the two reconstructed networks to reveal the roleplayed by them in crazing of polymers. Our analysis captured various stages ofcrazing through specific trends in the network measures for Van der Waalsnetworks and entanglement networks. To further corroborate the effectiveness ofnetwork analysis in unraveling the underlying physics of crazing in polymers,we have contrasted the trends in network measures for Van der Waals networksand entanglement networks in the light of stress-strain behaviour and voidsstatistics during deformation. We find that Van der Waals network plays acrucial role in craze initiation and growth. Although, the entanglement networkwas found to maintain its structure during craze initiation stage, it was foundto progressively weaken and undergo dynamic changes during the hardening andfailure stages of crazing phenomena. Our work demonstrates the utility ofnetwork theory in quantifying the underlying physics of polymer crazing andwidens the scope of applications of network science to characterization ofdeformation mechanisms in diverse polymers.