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Stress singularity transition of generic wedges due to nanoelement layers
Sueda, T.,Jeon, I.,Sumigawa, T.,Kitamura, T. Pergamon Press ; Elsevier Science Ltd 2011 Engineering fracture mechanics Vol.78 No.16
The effect of a nanoelement interfacial layer on the stress singularity transitions of generic wedges is analyzed using the finite element method. The singularity transitions corresponding to changes in the vertical stiffness and the lateral stiffness of the nanoelement are examined. In general, high vertical stiffness and high lateral stiffness yield singularities close to those of wedges without nanoelements while low vertical stiffness and low lateral stiffness cause the elimination of the stress concentration. Under high vertical stiffness and low lateral stiffness the singularity is dependent on wedge shapes and the dependence is analyzed in terms of the constraint condition.
Asynchronous cracking with dissimilar paths in multilayer graphene
Jang, Bongkyun,Kim, Byungwoon,Kim, Jae-Hyun,Lee, Hak-Joo,Sumigawa, Takashi,Kitamura, Takayuki The Royal Society of Chemistry 2017 Nanoscale Vol.9 No.44
<P>Multilayer graphene consists of a stack of single-atomic-thick monolayer graphene sheets bound with π-π interactions and is a fascinating model material opening up a new field of fracture mechanics. In this study, fracture behavior of single-crystalline multilayer graphene was investigated using an<I>in situ</I>mode I fracture test under a scanning electron microscope, and abnormal crack propagation in multilayer graphene was identified for the first time. The fracture toughness of graphene was determined from the measured load-displacement curves and the realistic finite element modelling of specimen geometries. Nonlinear fracture behavior of the multilayer graphene is discussed based on nonlinear elastic fracture mechanics.<I>In situ</I>scanning electron microscope images obtained during the fracture test showed asynchronous crack propagation along independent paths, causing interlayer shear stress and slippages. We also found that energy dissipation by interlayer slippages between the graphene layers is the reason for the enhanced fracture toughness of multilayer graphene. The asynchronous cracking with independent paths is a unique cracking and toughening mechanism for single-crystalline multilayer graphene, which is not observed for the monolayer graphene. This could provide a useful insight for the design and development of graphene-based composite materials for structural applications.</P>