A Molecular Dynamic Study of Nano-Fracture of C3N

2019 ◽  
Author(s):  
MD Imrul Reza Shishir ◽  
Alireza Tabarraei
Keyword(s):  
Energy Release Rate ◽  
Crack Length ◽  
Energy Release ◽  
Release Rate ◽  
Chemical Properties ◽  
Critical Energy ◽  
Two Dimensional ◽  
Critical Energy Release Rate ◽  
Fracture Properties ◽  
Zigzag Direction

Abstract The recently synthesized two–dimensional C3N is a graphene–like two–dimensional material with remarkable electronic, optoelectronic, thermal, mechanical and chemical properties. Molecular dynamics (MD) simulation is used to investigate the fracture properties of C3N. Cracks with different geometry and orientations are used to investigate how the crack tip configuration and orientation impact the fracture properties of C3N. The results show that regardless of their initial orientation, at microscale cracks always tend to propagate along a zigzag direction. The MD results are used to estimate the critical energy release rate of C3N. The critical energy release rate of both armchair and zigzag cracks increases with the decrease of crack length when the crack length is less than 7 nm. The critical energy release rate for armchair and zigzag cracks longer than 7 nm is respectively 10.16 J/m2 and 8.52 J/m2 which are significantly lower than those of graphene.

scholarly journals Study of Strain-Hardening Behaviour of Fibre-Reinforced Alkali-Activated Fly Ash Cement

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4015
Author(s):  
Hyuk Lee ◽  
Vanissorn Vimonsatit ◽  
Priyan Mendis ◽  
Ayman Nassif
Keyword(s):  
Fly Ash ◽  
Energy Release Rate ◽  
Strain Hardening ◽  
Energy Release ◽  
Release Rate ◽  
Critical Energy ◽  
Critical Energy Release Rate ◽  
Pull Out ◽  
Alkali Activated ◽  
Alkali Activated Cement

This paper presents a study of parameters affecting the fibre pull out capacity and strain-hardening behaviour of fibre-reinforced alkali-activated cement composite (AAC). Fly ash is a common aluminosilicate source in AAC and was used in this study to create fly ash based AAC. Based on a numerical study using Taguchi’s design of experiment (DOE) approach, the effect of parameters on the fibre pull out capacity was identified. The fibre pull out force between the AAC matrix and the fibre depends greatly on the fibre diameter and embedded length. The fibre pull out test was conducted on alkali-activated cement with a capacity in a range of 0.8 to 1.0 MPa. The strain-hardening behaviour of alkali-activated cement was determined based on its compressive and flexural strengths. While achieving the strain-hardening behaviour of the AAC composite, the compressive strength decreases, and fine materials in the composite contribute to decreasing in the flexural strength and strain capacity. The composite critical energy release rate in AAC matrix was determined to be approximately 0.01 kJ/m 2 based on a nanoindentation approach. The results of the flexural performance indicate that the critical energy release rate of alkali-activated cement matrix should be less than 0.01 kJ/m 2 to achieve the strain-hardening behaviour.

Effect of Characteristic Parameters of Exponential Cohesive Zone Model on Mode I Fracture of Laminated Composites

2012 ◽  
Vol 525-526 ◽  
pp. 409-412 ◽  
Author(s):  
Guo Wei Zhu ◽  
Yu Xi Jia ◽  
Peng Qu ◽  
Jia Qi Nie ◽  
Yun Li Guo
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Laminated Composites ◽  
Peak Load ◽  
Interfacial Strength ◽  
Critical Energy ◽  
Mode I ◽  
Zone Model ◽  
Critical Energy Release Rate

Delamination is a particularly dangerous damage mode of high performance laminated composites. In order to describe the composites ductile cracking and its progressive evolution accurately, the adjusted exponential cohesive zone model (CZM) is adopted, which correlates the tensile traction with the corresponding interfacial separation along the fracturing interfacial zone. At first the adjusted exponential CZM is used to simulate the mode I delamination of the standard double cantilever beam (DCB). The simulated results are in good agreement with the corrected beam theory and the corresponding experimental results. Then in order to research how the interfacial properties influence the mode I fracture, the interfacial strength and the critical energy release rate are studied. The main results are obtained as follows. The interfacial strength plays a crucial role in the laminated composites delamination onset, and it affects the peak load significantly if there is not a pre-crack. Once the delamination propagation begins to occur in the laminated composites, the responses of the load-displacement plots are relatively insensitive to the interfacial strength, and only the critical energy release rate is of critical importance. Furthermore, the peak load increases with the increase of the critical energy release rate and interfacial strength.

Ductile Tearing Prediction in Welds Considering Hydrogen Embrittlement

2013 ◽  
Author(s):  
Vincent Robin ◽  
Philippe Gilles ◽  
Philippe Mourgue ◽  
David Tchoukien
Keyword(s):  
Residual Stress ◽  
Hydrogen Embrittlement ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Crack Front ◽  
Hydrogen Diffusion ◽  
Critical Energy ◽  
Critical Energy Release Rate ◽  
Welding Operation

Some flaws may appear in metal components, in the weld region, and more especially in the case of electron beam girth weld in the slope area of the process (start and stop of the welding operation). These initial flaws can growth with delay even without any external loads. Indeed close to the junction, the material undergoes the combination of high tensile residual stresses due to welding operation and the presence of hydrogen brought by manufacturing process. Hydrogen assisted cracking is then suspected to explain the origin of crack growth through hydrogen embrittlement of the base metal. To understand by numerical modeling, at least qualitatively, the scenario of appearance of such cracks and their evolution, without any external load or under pressure load, the proposed approach consists first in simulating the welding process and its consequences on residual stress distribution and hydrogen concentrations [1]. The hydrogen diffusion computation is pursued after the welding operation simulation in order to highlight the most critical moment at which macroscopic defects may appear. Then, a macroscopic defect is created in the so determined critical zone, the stability of which is studied by estimating the energy release rate at the crack front and by comparing these values with experimental data such as the critical energy release rate at initiation and the tearing resistance curves which may depend on the hydrogen content. So, it is numerically possible to propagate the defect in the time, considering hydrogen diffusion and residual stress rebalancing, by successive crack front definition performed as the crack tip region exceeds the critical energy release rate [14]. Finally, the evolution of the defect is estimated in the same way under pressure test loading conditions. Results and discussions are presented to propose an engineering approach for the design assessment of such specific weld junctions with a low and hydrogen dependant toughness.

Experimental study on the effect of interface fiber orientation and utilized delamination initiation techniques on fracture toughness of glass/epoxy composite laminates

2016 ◽  
Vol 35 (23) ◽  
pp. 1722-1733 ◽  
Author(s):  
Masood Nikbakht ◽  
Hossein Hosseini Toudeshky ◽  
Bijan Mohammadi
Keyword(s):  
Fracture Toughness ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Composite Laminates ◽  
Standard Procedure ◽  
Damage Zone ◽  
Critical Energy ◽  
Critical Energy Release Rate ◽  
Interface Layers

Critical energy release rate for delamination initiation in composites as a material property, supposed to be independent from non-material variables. However, a thorough literature review presented in this study shows that in many cases it may vary with the variation of layup configuration or geometrical and dimensions. This study is aimed to investigate the effect of interface layers orientation on fracture toughness by eliminating the other influential parameters such as stacking sequence, by selecting the anti-symmetric layup configuration of Double Cantilever Beam, [Formula: see text], in which θ will be 0°, 30°, 45° and 60°. The energy release rates data have been calculated using different criteria and techniques to obtain the load and displacement at initial crack growth and the results were compared with the standard methods. The damage zone near the crack tip is also illustrated before and after the crack propagation by microscopic images of delamination front, and discussed for all investigated interface fiber angles. Experimental results show that the effect of interface layers orientation on fracture toughness of the investigated layup configurations based on the nonlinear technique as a standard procedure is negligible while other techniques show a considerable changes in the calculated energy release rate with the increase of interface layers angle from zero to 60 degrees.

Determination of Energy Release Rate Through Sequential Crack Extension

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Scott McCann ◽  
Gregory T. Ostrowicki ◽  
Anh Tran ◽  
Timothy Huang ◽  
Tobias Bernhard ◽  
...  
Keyword(s):  
Finite Element ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Critical Energy ◽  
External Work ◽  
Critical Energy Release Rate ◽  
Conservation Of Energy

A method to determine the critical energy release rate of a peel tested sample using an energy-based approach within a finite element framework is developed. The method uses a single finite element model, in which the external work, elastic strain energy, and inelastic strain energy are calculated as nodes along the crack interface are sequentially decoupled. The energy release rate is calculated from the conservation of energy. By using a direct, energy-based approach, the method can account for large plastic strains and unloading, both of which are common in peel tests. The energy rates are found to be mesh dependent; mesh and convergence strategies are developed to determine the critical energy release rate. An example of the model is given in which the critical energy release rate of a 10-μm thick electroplated copper thin film bonded to a borosilicate glass substrate which exhibited a 3.0 N/cm average peel force was determined to be 20.9 J/m2.

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