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Molecular Simulation of Anisotropic Stress and Structure in polymers

Electronic Theses of Indian Institute of Science

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Field Value
 
Title Molecular Simulation of Anisotropic Stress and Structure in polymers
 
Creator Srivastava, Prashant Kumar
 
Subject Anisortropic stress
Molecular Dynamic Simulations
Polymers
Linear Polymer
Elastomers
Sinusoidal Strain Loading
Elastomers - Stress-strain Behavior
Organic Chemistry
 
Description This dissertation presents a numerical study using molecular dynamic simulations
that interrogates the polymer structure as it is strained continuously in time and correlates it with the stress developed in it. We investigate the role of external control variables such as temperature, strain-rate, chain length, and density. At temperatures higher than glass transition, stress anisotropy is reduced even though bond stretch is greater at higher temperatures. There is a significant increase in stress level with increasing density. At faster rates of loading stress anisotropy increases. Deformation is mostly due to bond stretch and bond bending rather than overall shape and size. Stress levels increase with longer chain length. Cross-linkers beyond a critical value of functionality cause increased constraint on the motion of monomers and uniaxial stress developed increases. Stacking of
chains also plays a dominant role in terms of excluded volume interactions. Low density, high temperature, low values of functionality of cross-linkers, and short chain length, facilitate chain uncoiling and chain slipping in crosslinked polymers. Uniaxial stress in linear polymers, on the other hand, is only mildly in uenced by temperature. Sinusoidal strain loading clearly reveals the viscoelastic nature of polymers. Internal structural parameters of
the chains such as bond length, bond angle show hysteresis during loading and unloading. However, parameters representing overall size and shape of chains do not display any hysteresis. Small size magnetic particles and their small volume fractions in polymers show no signi cant e ect of applied external magnetic eld on anisotropic stress. Stress increases with lowering temperature, increasing density, decreasing volume fraction of magnetic particles, and increasing chain length
 
Contributor Vankatraman, Kartik
 
Date 2018-02-14T21:37:58Z
2018-02-14T21:37:58Z
2018-02-15
2014
 
Type Thesis
 
Identifier http://hdl.handle.net/2005/3113
http://etd.ncsi.iisc.ernet.in/abstracts/3973/G26348-Abs.pdf
 
Language en_US
 
Relation G26348