On the effect of vacancy defect on the mechanical properties of gallium nitride nanosheets

2016 ◽  
Vol 30 (22) ◽  
pp. 1650151 ◽  
Author(s):  
Saeed Rouhi
Keyword(s):  
Mechanical Properties ◽  
Gallium Nitride ◽  
Tensile Loading ◽  
Md Simulations ◽  
Tensile Tests ◽  
Vacancy Defect ◽  
Ultimate Stress ◽  
Stress And Strain ◽  
Vacancy Defects ◽  
Fracture Evolution

Using molecular dynamics (MD) simulations, the influence of the vacancy defects on the mechanical properties of gallium nitride (GaN) nanosheets is investigated. Two types of defective nanosheets are studied. In one of them, only one atom is removed at the vacancies and in the other, the number of removed atoms is not limited. It is shown that GaN nanosheets with multiple vacancies have larger in-plane elastic modulus than nanosheets with single vacancies. Besides, the ultimate stress and strain of GaN nanosheets are computed. Compared to perfect nanosheet, a significant decrease is observed in the ultimate stress of GaN nanosheet with only 2% defect. By plotting the fracture evolution of nanosheets under uni-directional tensile loading, three different patterns are observed. Moreover, by using bi-directional tensile tests on the nanosheets, the bulk moduli of perfect and defective GaN nanosheets are computed.

Coupling effect of strain rate and temperature on tensile damage mechanism of polyphenylene sulfide reinforced by glass fiber (PPS/GF30)

2020 ◽  
pp. 089270572094422
Author(s):  
Mohammadali Shirinbayan ◽  
Joseph Fitoussi ◽  
Farid Kheradmand ◽  
Arash Montazeri ◽  
Peiyuan Zuo ◽  
...  
Keyword(s):  
Strain Rate ◽  
Glass Fiber ◽  
High Strain ◽  
Coupling Effect ◽  
Damage Mechanism ◽  
Tensile Tests ◽  
Ultimate Stress ◽  
Polyphenylene Sulfide ◽  
Stress And Strain ◽  
Strain Rates

Influence of loading temperature on the damage mechanism of polyphenylene sulfide (PPS) reinforced by glass fiber (PPS/GF30) under tension was experimentally studied from quasi-static (QS) to high strain rates. Two kinds of PPS/GF30 samples were prepared: PPS-0° and PPS-90° (correspond to fibers oriented parallel and perpendicular to the injection direction, respectively). After microscopic observation and thermomechanical characterizations by dynamic mechanical analysis, tensile tests up to failure with strain rates varying from 10−3 s−1 to 100 s−1 have been carried out at 25°C and 120°C with regard to PPS/GF30 glass transition temperature. To achieve the coupling effect of high strain rate and high temperature, a special chamber was designed to install on the servo-hydraulic machine. The results of QS tensile tests confirm the significant effect of fiber orientation and temperature on the Young’s modulus, the ultimate stress, and strain. High strain tensile test results showed that the PPS/GF30 composite is strain rate dependent at both temperatures. The results indicated that Young’s modulus remains constant by strain rate increasing at both temperatures while ultimate stress and strain are increased. No significant damage has been observed at 25°C in QS loading, whereas the macroscopic damage variable is increased to 20% at 120°C. Debonding at the fiber–matrix interface is the main damage mechanism at 120°C.

scholarly journals Compressive Behavior of Carbon Nanotube Reinforced Polypropylene Composites Under High Strain Rate: Insights From Molecular Dynamics

2021 ◽  
Author(s):  
Brijesh Mishra ◽  
Sumit Sharma
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotube ◽  
Strain Rate ◽  
Compressive Strain ◽  
Md Simulations ◽  
Vital Role ◽  
Key Factors ◽  
Single Walled Carbon Nanotube ◽  
Vacancy Defects ◽  
Polypropylene Composites

Abstract Since the discovery of carbon nanotubes (CNTs), these have received a lot of attention because of their unusual mechanical electrical properties. Strain rate is one of the key factors that play a vital role in enhancing the mechanical properties of nanocomposites. In this study, (4, 4) armchair single-walled carbon nanotube (SWCNT) was employed with the polymer matrix as polypropylene (PP). The influence of compressive strain rate on SWCNT/PP nanocomposites was evaluated using MD simulations, and mechanical properties have been predicted. Stone-Wales (SW) and vacancy defects, were integrated on the SWCNT. The maximum Young’s modulus (E) of 81.501 GPa was found for the pristine SWCNT/PP composite for a strain rate of 1010 s-1. The least value of E was 45.073GPa for 6% SW defective/PP composite for a strain rate of 108 s-1. While the 6% vacancy defective CNT/PP composite showed the lowest value of E as 39.57GPa for strain rate 108 s-1. It was found that the mechanical properties of SWCNT/PP nanocomposites decrease with the increase in percent defect. It was also seen that the mechanical properties were enhanced with the increment in the applied strain rate. The results obtained from this study could be useful for the researchers designing PP-based materials for compression loading to be used for biomedical applications.

Atomic Structure and Mechanical Properties of Defective Carbon Nanotube (7,7)

2016 ◽  
Vol 843 ◽  
pp. 78-84
Author(s):  
Sergey Anatolevich Sozykin ◽  
Valeriy Petrovich Beskachko ◽  
G.P. Vyatkin
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotube ◽  
Atomic Structure ◽  
Young Modulus ◽  
Vacancy Defect ◽  
First Principle ◽  
Single Vacancy ◽  
Elongation At Break ◽  
Vacancy Defects ◽  
Defect Type

The article presents the results of first-principle modeling of a defectless (7,7) carbon nanotube and (7,7) nanotubes containing single and double vacancy defects, as well as Stone–Wales defects. These types of defects are often found in real nanotubes and affect their properties. We have established that reliable results can be obtained by using models of more than 1.5 nm in length. It turned out that a single vacancy defect has the least influence on Young modulus, and double n type vacancy defect in the most influential. The elongation at break also depends on the defect type and is 30-60% less than for perfect tubes.

scholarly journals Computing grain boundary diagrams of thermodynamic and mechanical properties

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Chongze Hu ◽  
Yanwen Li ◽  
Zhiyang Yu ◽  
Jian Luo
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Md Simulations ◽  
Structural Disorder ◽  
Research Direction ◽  
Tensile Tests ◽  
Al Alloy ◽  
Structure Property ◽  
Scanning Transmission ◽  
Composition Structure

AbstractComputing the grain boundary (GB) counterparts to bulk phase diagrams represents an emerging research direction. Using a classical embrittlement model system Ga-doped Al alloy, this study demonstrates the feasibility of computing temperature- and composition-dependent GB diagrams to represent not only equilibrium thermodynamic and structural characters, but also mechanical properties. Specifically, hybrid Monte Carlo and molecular dynamics (MC/MD) simulations are used to obtain the equilibrium GB structure as a function of temperature and composition. Simulated GB structures are validated by aberration-corrected scanning transmission electron microscopy. Subsequently, MD tensile tests are performed on the simulated equilibrium GB structures. GB diagrams are computed for not only GB adsorption and structural disorder, but also interfacial structural and chemical widths, MD ultimate tensile strength, and MD tensile toughness. This study suggests a research direction to investigate GB composition–structure–property relationships via computing GB diagrams of thermodynamic, structural, and mechanical (or potentially other) properties.

YOUNG’S MODULUS AND POISSON’S RATIO OF MERPAUH, KAPUR AND SESENDUK SPECIES

2016 ◽  
Vol 78 (5-2) ◽  
Author(s):  
Rohana Hassan ◽  
Syed Syazaril Amri Syed Mubarat ◽  
Anizahyati Alisibramulisi
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Poisson’S Ratio ◽  
Young's Modulus ◽  
Poisson Ratio ◽  
Tensile Tests ◽  
Poisson's Ratio ◽  
Stress And Strain ◽  
Timber Species ◽  
Strength Capacity

Young’s Modulus and Poisson’s ratio are the mechanical properties that need to be determined for the production of engineering design or information for the numerical analysis of timber. In this study, Merpauh, Kapur and Sesenduk species were selected. This experimental investigation focuses on the elastic properties of those timber species. The Modulus of Elasticity (MOE) and Poisson’s ratio were determined by means of tensile tests. In addition, Modulus of Rigidity (MOR), tensile strength capacity and its moisture contents were also determined. The deformation during testing was measured by means of mechanical extensometer. The MOE of the studied species range from 36.7 N/mm2 to 119.2 N/mm2, whereas Poisson’s ratio values show less variability. The result of the study also shows that the mechanical properties for the species are related. The larger the density value, the larger value of stress and strain will be. Thus, the value of Poisson ratio will also increase, respectively.

scholarly journals Influence of Temperature with its Geometric and Failure Morphology Defects on the Mechanical Properties of Graphene: Molecular Dynamics Simulation (MDs)

2019 ◽  
pp. 17-26
Author(s):  
Muse Degefe Chewaka Liban ◽  
Dr. Prabhu Paramasivam
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Hexagonal Lattice ◽  
Vacancy Defect ◽  
Dynamics Simulation ◽  
Atomistic Modeling ◽  
Key Factors ◽  
Vacancy Defects ◽  
Influence Of Temperature ◽  
Failure Morphology

This paper addressed that graphene is a regular monolayer of carbon atoms settled in a 2 D-hexagonal lattice; which is listed among the strongest material ever measured with strength exceeding more than hundred times of steel. However, the strength of graphene is critically influenced by temperature, geometric & vacancy defects (VD). Defects are at all believed to worsen the mechanical toughness and reduce the strength of graphene sheet. They are revealed that stiffness and strength are the key factors in determining solidity and life span of any technological devices. Molecular dynamics-based atomistic modeling was performed to predict and quantify the effect of non-bonded interactions on the failure morphology of vacancy affected sheets of graphene. The defective sheet of graphene containing vacancy defect was simulated in conjunction with the non-bonded interactions experienced due to the presence of a pristine sheet of graphene.

Bone mechanical properties after exercise training in young and old rats

1990 ◽  
Vol 68 (1) ◽  
pp. 130-134 ◽  
Author(s):  
D. M. Raab ◽  
E. L. Smith ◽  
T. D. Crenshaw ◽  
D. P. Thomas
Keyword(s):  
Mechanical Properties ◽  
Dry Weight ◽  
Ultimate Stress ◽  
Moment Of Inertia ◽  
Female Rats ◽  
Stress And Strain ◽  
Nonsignificant Trend ◽  
Fischer 344 ◽  
Old Rats ◽  
Both Bones

The effects of a 10-wk training regimen on the mechanical properties of the femur and humerus were evaluated in 2.5- and 25-mo-old Fischer 344 female rats. The rats trained on a rodent treadmill 5 days/wk for 10 wk. Duration, grade, and speed increased until the rats maintained 1 h/day at 15% grade and either 15 m/min (old rats) or 36 m/min (young rats). Excised bones were mechanically tested with a 3-point flexure test for mechanical properties of force, stress, and strain. Fat-free dry weight (FFW) and moment of inertia were also obtained. With aging, similar increases were observed in both the femur and humerus for FFW, moment of inertia, and force. Ultimate stress was reduced in the senescent femur while strain was elevated; a similar but nonsignificant trend was observed in the humerus. Irrespective of age, training increased FFW in the femur and, to a lesser degree, in the humerus. Breaking force was elevated for both bones after training. In young and old bones, the training-induced differences in bone mass and force were similar, despite differences in training intensity. In the old trained rats, femur ultimate stress was greater than that in control rat femurs and similar to that in young rat femurs. The results of the present study indicate that training effects were not limited by age.

scholarly journals Thermal and Mechanical Properties of Flexible Poly(L-lactide)-b-polyethylene Glycol-b-poly(L-lactide)/Microcrystalline Cellulose Biocomposites

2021 ◽  
Vol 33 (9) ◽  
pp. 2135-2142
Author(s):  
Jenjira Jirum ◽  
Yodthong Baimark
Keyword(s):  
Mechanical Properties ◽  
Polyethylene Glycol ◽  
Microcrystalline Cellulose ◽  
Tensile Tests ◽  
Stress And Strain ◽  
Melt Blending ◽  
Thermal And Mechanical Properties ◽  
Biocomposite Films ◽  
Phase Compatibility ◽  
Thermal Stability Of

In this work, flexible biocomposites were prepared through melt blending using flexible poly(L-lactide)- b-polyethylene glycol-b-poly(L-lactide) (PLLA-PEG-PLLA) as a matrix and microcrystalline cellulose (MCC) as a filler. The effects of the addition of MCC on the thermal, morphological and mechanical properties of PLLA-PEG-PLLA/MCC biocomposites were investigated compared to PLLA/MCC biocomposites. Thermal stability of both PLLA and PLLA-PEG-PLLA from thermogravimetric analysis (TGA) was improved by MCC blending. Scanning electron microscopy (SEM) of the biocomposites exhibited good phase compatibility between PLLA-PEG-PLLA matrix-MCC filler. From tensile tests, the stress and strain at break of the PLLA/MCC and PLLA-PEG-PLLA/MCC biocomposite films decreased while the Young’s modulus increased as the MCC content increased. The strain at break of PLLA-based and PLLA-PEG-PLLA based biocomposite films containing 20 wt.% MCC were 2% and 162%, respectively. Thus, the PLLA-PEG-PLLA/MCC biocomposites have potential to be used as flexible bioplastics for packaging applications.

Progressive damage characteristics of screwed single-lap CFRPI-metal joint subjected to tensile loading at RT and 350°C

2021 ◽  
pp. 002199832098559
Author(s):  
Yun-Tao Zhu ◽  
Jun-Jiang Xiong ◽  
Chu-Yang Luo ◽  
Yi-Sen Du
Keyword(s):  
Damage Model ◽  
Tensile Loading ◽  
Tensile Tests ◽  
Displacement Curve ◽  
Progressive Damage ◽  
Damage Characteristics ◽  
Metal Joint ◽  
Static Tensile ◽  
Strength And Stiffness ◽  
Progressive Damage Model

This paper outlines progressive damage characteristics of screwed single-lap CFRPI-metal joints subjected to tensile loading at RT (room temperature) and 350°C. Quasi-static tensile tests were performed on screwed single-lap CCF300/AC721-30CrMnSiA joint at RT and 350°C, and the load versus displacement curve, strength and stiffness of joint were gauged and discussed. With due consideration of thermal-mechanical interaction and complex failure mechanism, a modified progressive damage model (PDM) based on the mixed failure criterion was devised to simulate progressive damage characteristics of screwed single-lap CCF300/AC721-30CrMnSiA joint, and simulations correlate well with experiments. By using the PDM, the effects of geometry dimensions on mechanical characteristics of screwed single-lap CCF300/AC721-30CrMnSiA joint were analyzed and discussed.

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