Fracture Toughness Characteristics of Stacked Bilayer Graphene via Far‐Field Displacement Measurements

Abstract

Mechanical properties of graphene, e.g., strength, modulus, and fracture toughness are extremely sensitive to flaws. Here the fracture properties of stacked bilayer graphene sheets (SBLG) are reported, obtained via stacking two individually grown graphene sheets. The SBLG is presented here as a building block for flaw‐resilient nanomaterials. The fracture properties of freestanding SBLG sheets, suspended on transmission electron microscope (TEM) grids, are characterized by stretching the TEM grid inside an scanning electron microscope (SEM) chamber and monitoring the local displacements in real‐time. The fracture toughness is measured and expressed as a function of the critical displacement required to propagate existing cracks in the experiment via computational models. This approach decouples force and displacements measurements, and utilizes the known elastic modulus along with the known displacement boundary conditions at the onset of crack growth to estimate the far field force and stress. This strategy represents a breakthrough in nanoscale fracture mechanics for statistical analysis and high throughput experimens on multiple samples at a time. Results demonstrate that the SBLG is markedly tougher than as‐grown single or multilayer graphene, with a mode I fracture toughness of ≈28.06 ± 7.5 MPa. The mechanisms leading to a higher toughness of SBLG are also analyzed and discussed.

Impact of metastable graphene-diamond coatings on the fracture toughness of silicon carbide

“…2e), probably due to the indentation size effect 10,37,38 and/or approximation in the determination of the contact area. The asymptotic hardness of a bare SiC(0001) is around 19 GPa, which is consistent with the values reported in the literature (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)).…”

“…The results can be explained considering the graphene-diamene phase transition occurring under the indenter 17,22 while the rest of the coating remains in the ultra-tough graphene phase. [24][25][26]…”

“…1b) 17,19,20,22 while the rest of the coating remains in the ultra-tough graphene phase. 24–26 This study opens new venues for understanding hardness and toughness in metastable systems and for the applications in protective coatings, body armor, and automobile, aerospace, and microelectromechanical systems.…”

Exploring fracture of H-BN and graphene by neural network force fields

“…Given the challenges associated with fabricating and implementing TBG-based devices, the failure or shaping in negative or positive points of view, respectively, led by the fracture of TBGs remains a technical concern to be addressed [60,61]. One of the distinct and interesting problems on this topic is the interaction between cracks in neighboring layers, which could potentially toughen the structures by shielding the stress field or modifying the crack paths [52,62]. However, an accurate and efficient FF is necessary to predict the crack paths in reasonably sized models [37], to produce theoretical predictions that can be directly compared to experimental data [19,20].…”