Influence of nanofiller agglomeration on fracture properties of polymer nanocomposite: Insights from atomistic simulation

Nanofillers tend to agglomerate inside the matrix of a polymer nanocomposite (PNC). Crack propagation mechanism gets modified in various ways near these agglomerated regions, which adversely affects the performance of nanocomposite. While such observations are reported in the literature, a detailed atomistic-scale study quantifying and analyzing these changes in fracture properties has not been reported. Reactive molecular dynamics simulations are conducted in this work to study the effects of agglomeration on fracture properties. The model material here is polymethyl methacrylate (PMMA) with carbon nanotube (CNT) reinforcement. Generally functionalization improves the resistance of PNC to crack propagation due to enhanced interfacial bonding. However, for agglomerated CNTs even functionalization does not improve the fracture toughness, since the crack propagates completely through the polymer matrix. Thus the CNTs do not participate in resisting the crack. Furthermore, the shear strain distribution along the CNT surface revealed that the CNTs and the polymer surrounding them act as a monolithic unit, resulting in reduction in fracture toughness and ductility. The agglomerated CNTs are also found to contribute towards strain accumulation and failure of PNC at a lower global strain level. These atomic-scale insights help in better understanding of damage mechanics of a PNC.

Automated summary

Nanofillers tend to agglomerate inside the matrix of a polymer nanocomposite, which modifies the crack propagation mechanism and adversely affects the fracture properties. Reactive molecular dynamics simulations were conducted to study the effects of agglomeration on fracture properties of polymethyl methacrylate (PMMA) with carbon nanotube (CNT) reinforcement. It was found that agglomerated CNTs do not improve the fracture toughness even with functionalization, and they contribute to strain accumulation and failure of the nanocomposite at a lower global strain level.