Molecular Dynamics Simulation Of Amorphous Linear Polymer During Deformation

Polymer materials, because of its excellent properties, are widely used in people's daily life, and have received special attention of researchers. But understanding the complicated relationship between structure and property of polymers is still a puzzling problem of research community. Conventional experimental apparatus, such as the AFM, SEM and X-ray diffraction spectrumetc, can only observe either the local topography, or obtain the overall average physical properties of materials. With these methods, it is impossible to achieve changes of internal microstructure during deformation, And also it is difficult to implement real-time observation. On the other hand, the computer simulation opened another door for researchers in solving these problems, and implement real-time observation of the internal structure of polymers during deformation.Molecular dynamics simulation was used to study the relationship between the internal structure and properties of amorphous linear polymer during deformation. The microstructual essence of the time-temperature equivalence principle was studied. The influences of temperature, strain rate, chain configurations, and time-step were investigated. The experimental results show that the simulated stress-strain curves of the amorphous linear polymer exhibit elastic, yield, strain softening and stress hardening, the materials' Young's modulus and yield stress decrease with increasing temperature and strain rate, at the same time, the temperature influence the distribution of bond length, bond angle and dihedral angle. Meanwhile the temperature and strain rate affect the entanglement, orientation and radius of gyration.In addition, the standard deviation of the stress-strain curves and the energy analysis were used to explore the scope and influence factors of the time-temperature equivalence principle. And these methods were also used to study the effect of temperature and strain rate on mechanical properties. The experimental results show that the applicable scope of simulated date of amorphous linear polymer agree with the WLF equation, at the same time, the temperature and strain rate affect the microstructural charactors such as the bond length, bond angle, the dihedral angle and non-bonded interactions(Van der Waals interactions) to implement the controlling of macro mechanical properties.