A cohesive law for interfaces in graphene/hexagonal boron nitride heterostructure

Graphene/hexagonal boron nitride (h-BN) heterostructure has showed great potential to improve the performance of graphene device. We have established the cohesive law for interfaces between graphene and monolayer or multi-layer h-BN based on the van der Waals force. The cohesive energy and cohesive strength are given in terms of area density of atoms on corresponding layers, number of layers, and parameters in the van der Waals force. It is found that the cohesive law in the graphene/multi-layer h-BN is dominated by the three h-BN layers which are closest to the graphene. The approximate solution is also obtained to simplify the expression of cohesive law. These results are very useful to study the deformation of graphene/h-BN heterostructure, which may have significant impacts on the performance and reliability of the graphene devices especially in the areas of emerging applications such as stretchable electronics

Coarse-Graining and Renormalization of Atomistic Binding Relations and Universal Macroscopic Cohesive Behavior

We present two approaches for coarse-graining interplanar potentials and determining the corresponding macroscopic cohesive laws based on energy relaxation and the renormalization group. We analyze the cohesive behavior of a large---but finite---number of interatomic planes and find that the macroscopic cohesive law adopts a universal asymptotic form. The universal form of the macroscopic cohesive law is an attractive fixed point of a suitably-defined renormalization-group transformation.Comment: 15 pages, 6 figures, submitted to the Journal of the Mechanics and Physics of Solid

Use of cohesive elements in fatigue analysis

Cohesive laws describe the resistance to incipient separation of material surfaces. A cohesive finite element is formulated on the basis of a particular cohesive law. Cohesive elements are placed at the boundary between adjacent standard volume finite elements to model fatigue damage that leads to fracture at the separation of the element boundaries per the cohesive law. In this work, a cohesive model for fatigue crack initiation is taken to be the irreversible loadingunloading hysteresis that represents fatigue damage occuring due to cyclic loads leading to the initiation of small cracks. Various cohesive laws are reviewed and one is selected that incorporates a hysteretic cyclic loading that accounts for energetic dissipative mechanisms. A mathematical representation is developed based on an exponential effective load-separation cohesive relationship. A three-dimensional cohesive element is defined using this compliance relationship integrated at four points on the mid-surface of the area element. Implementation into finite element software is discussed and particular attention is applied to numerical convergence issues as the inflection point between loading and 'unloading in the cohesive law is encountered. A simple example of a displacementcontrolled fatigue test is presented in a finite element simulation. Comments are made on applications of the method to prediction of fatigue life for engineering structures such as pressure vessels and piping

Comparison between cohesive zone models and a coupled criterion for prediction of edge debonding

International audienceThe onset of edge debonding within a bonded specimen submitted to bending is modeled with two numerical approaches: the coupled criterion and the cohesive zone model. The comparison of the results obtained with the both approaches evidences that (i) the prediction of edge debonding strongly depends on the shape of the cohesive law and (ii) the trapezoidal cohesive law is the most relevant model to predict the edge debonding as compared with the coupled criterion

Dynamic Fracturing Simulation of Brittle Material using the Distinct Lattice Spring Method with a Full Rate-Dependent Cohesive Law

A full rate-dependent cohesive law is implemented in the distinct lattice spring method (DLSM) to investigate the dynamic fracturing behavior of brittle materials. Both the spring ultimate deformation and spring strength are dependent on the spring deformation rate. From the simulation results, it is found that the dynamic crack propagation velocity can be well predicted by the DLSM through the implemented full rate-dependent cohesive law. Furthermore, a numerical investigation on dynamic branching is also conducted by using the DLSM cod

Theoretical and numerical investigation on internal instability phenomena in composite materials

Instability phenomena occurring in the microstructure of composite materials are investigated. To this aim, a complete description of the mechanical behavior of bi-material interfaces in composite materials requires the definition of both a cohesive law involving damage for the debonding stage, and a contact model during the closure of the interface. Both formulations are herein presented and implemented in the FE code FEAP. Numerical examples showing the transition from a snap-back instability to a stable mechanical response are presented

A combined experimental-numerical study to tensile behaviour of limestone

In this paper, a combined experimental-computational study of double-edge notched stone specimen subject to cyclic tensile loading is presented. In the experimental part, the load-deformation response and the local displacement field are recorded. Both experimental results are used to validate a numerical model for the description of fracture within finite elements. The model uses displacement discontinuities to model cracks. These discontinuities are implemented using the partition of unity property of finite element shape functions. In the discontinuity, a combined damage-plasticity cohesive law is used. Numerical simulations are compared with experimental observations

Novel experimental procedure and determination of full displacement fields of delaminating composite layer interfaces for evaluation of the mode II cohesive law

AbstractA novel mode II fracture test setup based on a simple tensile loading scenario with a discontinuous ply specimen is proposed in the paper as the first step towards determination of the cohesive law of composite layer interfaces. Key outputs of the procedure are the full displacement fields obtained by correlation of high resolution SEM images taken during in-situ tensile tests. Analysis of the full displacement fields at subsequent stress levels allow for unique analysis of the damage zone and direct determination of the displacement jumps across the interface. The next phase of the work is the evaluation of the shear stresses at the interface necessary to determine the cohesive law