Student 12

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Background

Recent polymer based composites offer a wide range of promising applications because of their much-enhanced properties arising from the reinforcement of nanoparticles. However, further development of such nanomaterials depends on the fundamental understanding of their hierarchical structures and behaviors, which requires multiscale modeling and simulation strategies to provide seamless coupling among various length and time scales. [1] The importance of multiscale simulation strategies in the understanding and predictive capabilities of polymeric composites include understanding the thermodynamics and kinetics of formation, molecular structure and dynamics, morphology, processing behaviors, and mechanical properties. The proposed computational methods to understand the behavior of polymeric composites, includes molecular scale (e.g., molecular dynamics, Monte Carlo), microscale (e.g., Brownian dynamics, dissipative particle dynamics, lattice Boltzmann, time-dependent Ginzburg–Landau method, dynamic density functional theory method) to mesoscale and macroscale (e.g., micromechanics, equivalent-continuum and self-similar approaches, finite element method).

Polymeric Composite Overwrap Pressure Vessel (COPV) Multiscale Modeling

COPV) Multiscale Modeling

Structural Scale Research

The ISV constants required for the structural scale modeling (FEA simulation) will be developed from lower length scale models. The ISV formulation will encompass a constitutive relationship for the material systems addressing the mechanical behavior of the materials with regards to processing, performance, damage tolerance, aging and environment.

Macroscale Research

The macroscale needs the following information: Elastic modulus, high rate versus low rate effects, PC density, temperature dependence for both elasticity and plasticity, the bonding and mobility which defines plastic deformation, particle interactions, and particle–crack interactions. FEA is used here to assess the synergistic effects on the entire system or component; providing a solution to external conditions, which is then used to determine the life cycle of the material.

Mesoscale Research

Simulations at this length scale prove helpful when quantifying how particles, voids, hardening rules, crystalline plasticity and the surrounding matrix interact. Discrete Dislocations explicitly accounts for all the kinematics and kinetics of dislocation motion and interactions including the geometrical attributes and short-range interactions of dislocations. [2]

Microscale Research

Analysis at this scale will conclude whether cracks were more likely to nucleate in the inter- dendrites/fibers/ribbons/voids structure etc. Moreover, the extended carbon ribbons, layered to form the fiber, are simulated by a coarse grain analysis to determine the ribbon’s strength. The carbon ribbons do not contain a grain structure, but coarse grain analysis can predict deflections. Also, using the cross-linking information the Void/ Crack nucleation and growth can be determined by finite element analysis for Epoxy.

Nanoscale Research

The nanoscale also known as atomistic length scale will focus on high rate mechanisms and dislocations. EAM/MEAM can provide information on dislocations at the interfaces of the high rate mechanisms. The MEAM simulation will provide information on where dislocations would occur up to the microscale.

Electronic Structure Research

The lowest length scale presented by Integrated Computational Materials Engineering (ICME) is the Electronics Scale. Density Function Theory (DFT) is commonly used to return the elasticity values needed at the atomistic scale simulations as well as the continuum scale. In the context of bridging the DFT calculations to the higher atomic scale simulations, it is important to get a few material properties in order to develop a successful semiempirical potential for something like the embedded atom method (EAM) or modified embedded atom method (MEAM) potentials such that the potentials can reproduce several materials or mechanical properties as accurately as possible. When the EAM/ MEAM potentials do not have experimental basis to be developed, then DFT results can be used to replace the needed data. [3]

References

  1. Russell, R., “Composite Overwrapped Pressure Vessels (COPV) Materials Aging Issues,” Materials Science and Technology; Houston, TX; Report Number KSC-2010-249, Pages 17-21 Oct. 2010.
  2. Wing Kam Liu, Sukky Jun, and Dong Qian, “Computational Nanomechanics of Materials,” Journal of Computational and Theoretical Nanoscience Vol. 5, Pages 1-27, 2008.
  3. Horstemeyer, M.F., Integrated Computational Materials Engineering (ICME) for Metals: Reinvigorating Engineering Design with Science, Wiley Press, 2012.
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