Fracture of monolayer germanene: A molecular dynamics study

2018 ◽  
Vol 32 (22) ◽  
pp. 1850241 ◽  
Author(s):  
Minh-Quy Le
Keyword(s):  
Molecular Dynamics ◽  
Stress Intensity Factor ◽  
Tensile Strength ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Critical Stress ◽  
Axial Strain ◽  
Critical Stress Intensity Factor ◽  
Monolayer Graphene ◽  
Fracture Properties

Molecular dynamics simulations with Tersoff potential were performed to study the fracture properties of monolayer germanene at 300 K. The two-dimensional (2D) Young’s modulus, 2D tensile strength and axial strain at the tensile strength of pristine monolayer germanene are about 36.0 and 37.5 N/m; 5.1 and 4.6 N/m; 21.4 and 15.9%, in the zigzag and armchair directions, respectively. Griffith theory was applied to compute the critical stress intensity factor. Compared to monolayer graphene, the critical stress intensity factor of monolayer germanene is much smaller. Fracture pattern and effects of the initial crack length on the fracture properties are also studied. Results are useful for future design and applications of this 2D material.

scholarly journals Fracture properties of fibre and nano reinforced composite structures

2007 ◽  
Author(s):  
◽  
Avinash Ramsaroop
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Composite Structures ◽  
Critical Stress ◽  
Strain Energy Release ◽  
Propagation Rate ◽  
Critical Stress Intensity Factor ◽  
Fracture Properties ◽  
Load Carrying

Interlaminar cracking or delamination is an inherent disadvantage of composite materials. In this study the fracture properties of nano and fibre-reinforced polypropylene and epoxy composite structures are examined. These structures were subjected to various tests including Single Edge Notched Bend (SENB) and Mixed Mode Bending (MMB) tests. Polypropylene nanocomposites infused with 0.5, 1, 2, 3 and 5 weight % nanoclays showed correspondingly increasing fracture properties. The 5 weight % specimen exhibited 161 % improvement in critical stress intensity factor (KIC) over virgin polypropylene. XRD and TEM studies show an increase in the intercalated morphology and the presence of agglomerated clay sites with an increase in clay loading. The improvement in KIC values may be attributed to the change in structure. Tests on the fibre-reinforced polypropylene composites reveal that the woven fibre structure carries 100 % greater load and exhibits 275 % lower crack propagation rate than the chopped fibre specimen. Under MMB conditions, the woven fibre structure exhibited a delamination propagation rate of 1.5 mm/min which suggests delamination growth propagates slower under Mode I dominant conditions. The woven fibre / epoxy structure shows 147 % greater tensile modulus, 63 % greater critical stress intensity factor (KIC), and 184 % lower crack propagation rate than the chopped fibre-reinforced epoxy composite. MMB tests reveal that the load carrying capability of the specimens increased as the mode-mix ratio decreased, corresponding to an increase in the Mode II component. Delamination was through fibre–matrix interface with no penetration of fibre layers. A failure envelope was developed and tested and may be used to determine the critical applied load for any mode-mix ratio. The 5 weight % nanocomposite specimen exhibited a greater load carrying capability and attained a critical stress intensity factor that was 10 % less than that of the fibre-reinforced polypropylene structure, which had three times the reinforcement weight. Further, the nanocomposite exhibited superior strain energy release rates to a material with ten times the reinforcement weight. The hybrid structure exhibited 27 % increase in tensile modulus over the conventional fibre-reinforced structure. Under MMB conditions, no significant increase in load carrying capability or strain energy release rate over the conventional composite was observed. However, the hybrid structure was able to resist delamination initiation for a longer period, and it also exhibited lower delamination propagation rates.

Probing the Critical Stress Intensity Factor for Slip Transfer across Grain Boundaries by Subgranular Indentation Alfonso

2000 ◽  
Vol 649 ◽  
Author(s):  
H.W. Ngan ◽  
Y.L. Chiu
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Critical Stress ◽  
Critical Stress Intensity Factor ◽  
Square Root ◽  
Slip Transfer ◽  
Macroscopic Deformation

ABSTRACTBy analysing the relevant results in the literature, we have found that, when indentation is made on a subgranular level, the hardness varies roughly inversely with the square root of the distance between the indent and the grain boundary. This effect is analogous to the Hall-Petch effect for macroscopic deformation.

Stress Intensity at the Initiation of Instability by R Curve

2014 ◽  
Vol 592-594 ◽  
pp. 1160-1164 ◽  
Author(s):  
S. Sundaresan ◽  
B. Nageswara Rao
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Critical Stress ◽  
Mouth Opening ◽  
Compact Tension ◽  
Critical Stress Intensity Factor ◽  
Pressure Vessels ◽  
Crack Mouth Opening Displacement ◽  
Opening Displacement

The life expectancy or failure of aerospace pressure vessels is evaluated by the critical stress intensity determined by the crack growth resistance curve of a material. Load versus crack mouth opening displacement data is generated from the Compact Tension specimens made from the weld joints of maraging steel rocket motor segments. The steps involved to generate critical stress intensity factor is explained. A power law is adopted to model the crack extension in terms of stress intensity factor and determine the maximum failure load of weld specimens. Maximum failure loads of CT specimens obtained by test and analysis are presented.

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