Kavli Affiliate: Chiara Daraio
| First 5 Authors: Suyeong Jin, Suyeong Jin, , ,
| Summary:
Graphene is a material with potential applications in electric, thermal, and
mechanical fields, and has seen significant advancements in growth methods that
facilitate large-scale production. However, defects during growth and transfer
to other substrates can compromise the integrity and strength of graphene.
Surprisingly, the literature suggests that, in certain cases, defects can
enhance or, at most, not affect the mechanical performance of graphene. Further
research is necessary to explore how defects interact within graphene structure
and affect its properties, especially in large-area samples. In this study, we
investigate the interaction between two preexisting cracks and their effect on
the mechanical properties of graphene using molecular dynamics simulations. The
behavior of zigzag and armchair graphene structures with cracks separated by
distances ($W_textgap$) is analyzed under tensile loading. The findings
reveal that crack coalescence, defined as the formation of a new crack from two
existing crack tips, occurs for lower values of the distance between cracks,
$W_textgap$, resulting in a decline in the strength of structures. As
$W_textgap$ increases, the stress-strain curves shift upward, with the peak
stress rising in the absence of crack coalescence. The effective stress
intensity factor formulated in this study exhibits a clear upward trend with
increasing $W_textgap$. Furthermore, an increase in $W_textgap$ induces a
transition in fracture behavior from crack coalescence to independent
propagation with intercrack undulation. This shift in fracture behavior
demonstrates a brittle-to-ductile transition, as evidenced by increased energy
absorption and delayed failure. A design guideline for the initial crack
geometry is suggested by correlating peak stress with the $W_textgap$,
within a certain range.
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