Multiscale Modeling of Fiber Reinforced Nanoparticle-modified Polymer Composites
Multiscale Modeling of Fiber Reinforced Nanoparticle-modified Polymer Composites
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Composites should be as light as possible, yet also rigid and sturdy to withstand thermo-chemo-mechanical loads experienced during their lifetime. The research aims to provide an innovative multiscale and multiphysics framework to investigate the material behavior of epoxy-based nanocomposites. Within the framework, different (mechanical-thermal-chemical) fields over multiple scales will be linked for the quantitative failure prediction of the polymer composites designed for engineering applications in lightweight rotor blades. The research goal is achieved by developing predictive models of failure for polymer composites based on atomistic, coarse-grained, numerical micromechanical homogenization, gradient-enhanced damage model, and phase-field model.
Gradient-enhanced damage modeling
Compact-tension fracture
Four point bending test
Phase-field fracture modeling of compact-tension test
Phase-field fracture modeling
Single-edge notched tension test
Single-edge notched shear test
Selected publications
A finite deformation phase-field fracture model for the thermo-viscoelastic analysis of polymer nanocomposites. Computer Methods in Applied Mechanics and Engineering 381 (2021) 113821.
A finite deformation gradient-enhanced damage model for nanoparticle/polymer nanocomposites: An atomistically-informed multiscale approach. Composite Structures 258 (2021): 113211.
Non-linear viscoelasticity of epoxy resins: Molecular simulation-based prediction and experimental validation. Polymer 180 (2019): 121722.
Multiscale Constitutive Modeling of Fiber-reinforced Polymer Nanocomposites
Multiscale Constitutive Modeling of Fiber-reinforced Polymer Nanocomposites
Continuing research activity concentrating in the field of synthetic composites has promised to develop a new class of high-performance glass fiber reinforced epoxy composites containing various nanofillers such as nanoparticles and nanotubes. The utilization of nanoscale fillers in polymer matrices has two important impacts on their material behavior. Firstly, nanoparticles show uniquely different physical and chemical properties from their bulk counterparts, which is related to having a larger portion of their atoms on the surface. Secondly, the extremely high surface-to-volume ratio of nanoparticles offers more contact surface area that can be 1000 times greater than that of micro-sized particles. This allows efficient load transfer from the matrix to the reinforcements that is the key to achieving high-performance materials. We proposed a multiscale approach to develop physically-based constitutive models for these composites, which accurately captures their nonlinear hyperelastic, time-dependent, and softening behavior at finite strain.
Selected publication
Viscoelastic damage behavior of fiber reinforced nanoparticle-filled epoxy nanocomposites: Multiscale modeling and experimental validation. Composites Part B: Engineering (2019): 107005.
A viscoelastic damage model for nanoparticle/epoxy nanocomposites at finite strain: A multiscale approach. Journal of the Mechanics and Physics of Solids 128 (2019): 162-180.
ANN-assisted Algorithm for Developing Coarse-grained Molecular Models for Polymer Composites
ANN-assisted Algorithm for Developing Coarse-grained Molecular Models for Polymer Composites
Adding nanoparticles to epoxy resins to tailor polymer nanocomposites with enhanced thermomechanical properties has attracted considerable attention for various engineering applications. This study proposes an artificial neural network-based optimization approach to develop coarse-grained (CG) models for molecular simulations of polymer nanocomposites. In the proposed framework, a neural network trained by all-atom simulation data is utilized to optimize CG force field parameters. The framework offers a computationally cost-effective algorithm to parametrize a CG force field for predicting the fracture properties of nanocomposites. Furthermore, the large-scale molecular simulations facilitated by CG models allow us to study the effect of nanoparticle agglomeration on the fracture behavior of the nanocomposites beyond the accessible time and length scales of all-atom simulations.
Interphase Characterization in Polymer Composites
Interphase Characterization in Polymer Composites
The mechanical properties of polymer composites are significantly influenced by interface and interphase interactions between fillers and the polymer matrix. The surface modification alters the chemical interaction between fillers and the matrix and thus very probably not only the interfacial bonding but also the morphology of the polymer itself in the vicinity of the fillers. However, experimental tests are not able to fully characterize the interface and interphase properties due to the small size of the involved phases and complicated interactions between them. To overcome these limitations, scientists have focused on the development of numerical models to support the characterization of interfacial properties. In this study, we proposed a simulation-based method to directly calculate the stress-strain relationship at the interphase between constituents using atomistic simulations. The extracted interphase properties were then transferred to the microscale for finite element modeling of agglomerated particle/polymer composites.
Selected publication
Elastic interphase properties of nanoparticle/epoxy nanocomposites: A molecular dynamics study.Composites Part B: Engineering 176 (2019): 107211.
Multiscale Simulation Studies on Failure Prediction of Polymer Composites
Multiscale Simulation Studies on Failure Prediction of Polymer Composites
An accurately theoretical model for the multiphysics (thermal, mechanical and water-induced) degradation mechanism of reinforced polyamide polymer composites was developed. The research funded by Bosch and NWO (Netherlands Organisation for Scientific Research) was aimed to provide an innovative multiscale approach to investigate fundamental aspects of failure in the polymer composites, and to develop a methodology for quantitative failure prediction of polymer composites designed for high temperature and pressure applications.
Selected publication
Effect of water content on the thermal degradation of amorphous polyamide 6, 6: A collective variable-driven hyperdynamics study. Polymer Degradation and Stability 146 (2017): 260-266.
Computational Modeling and Design of Lithium-ion Batteries
Computational Modeling and Design of Lithium-ion Batteries
Between 2014 and 2015, I studied the material properties of reinforced polymer composites to boost their revolutionary development and applications in design of lithium-ion batteries. In order to fulfill the objectives, a comprehensive program was proposed to investigate the thermo-mechanical properties of the polymer composites. For this, I developed coarse-grained molecular models for multidirectional carbon nanotube reinforced polymer composites. The principle of coarse-grained models is to map a set of atoms to a CG bead, which enables to extend the accessible time and length-scales while maintaining the molecular details of an atomistic system. The mapping scheme relates the atomistic coordinates of a structure to the bead positions in the CG model. The CG models provide a reduced picture and interpretation of complex molecular phenomena by averaging over unessential atomic details. It facilitates the study of molecular systems since (1) the total number of particles is reduced, (2) the interaction potentials are simplified and (3) the potential energy surface on which the molecules move is smoothened, leading to an acceleration of molecular simulations.
Coarse-grained simulation of crack propagation in CNT/polymer
Selected publications
Coarse-grained model of the J-integral of carbon nanotube reinforced polymer composites. Carbon 96 (2016): 1084-1092.
Tensile fracture behavior of short carbon nanotube reinforced polymer composites: A coarse-grained model. Composite Structures 134 (2015): 981-988.
Mechanical properties of carbon nanotube reinforced polymer nanocomposites: A coarse-grained model. Composites Part B: Engineering 80 (2015): 92-100.
Atomistically-informed Nonlocal Continuum Modeling of Nanoresonators
Atomistically-informed Nonlocal Continuum Modeling of Nanoresonators
The main objective of the research is to study the potential application of carbon nanotubes (CNTs) and graphene sheets (GSs) as nano-resonator sensors in the detection of atoms/molecules with vibration and wave propagation analyses. The hypothesis in the detection techniques is that atoms or molecules attached to the surface of the nano-resonator sensors would induce a recognizable shift in the resonant frequency of or wave velocity in the sensors. With this regard, a sensitivity index based on the shift in the resonant frequency of the sensors in the vibration analysis and/or a shift in wave velocity in the sensors in the wave propagation analysis is defined and examined. In order to achieve the objective, the vibration characteristics of CNTs and GSs are studied using molecular dynamics simulations and nonlocal continuum models. I developed beam, shell and plate models to study the vibration and wave propagation characteristics, and buckling stability of carbon nanotubes and graphene sheets. Next, the set of governing equations of motion was numerically solved by different methods such as finite element, differential quadrature and meshfree methods. The simulation results provide valuable information to study the dynamic behaviors of the two nano-materials and verify and calibrate plate and shell models based on the nonlocal continuum theory.
Wave propagation in a GS
Vibration of a GS in a gaseous environment
Vibration of a CNT
Impulse wave in an SWCNT
Selected publications
A review on the application of nonlocal elastic models in modeling of carbon nanotubes and graphenes. Computational Materials Science 51 (2012) 303–313.
Size-and temperature-dependent bending rigidity of graphene using modal analysis. Carbon 139 (2018): 334-341.
A review on nanomechanical resonators and their applications in sensors and molecular transportation. Applied physics reviews 2.2 (2015): 021301.
Detection of gas atoms with carbon nanotubes. Scientific reports 3 (2013): 1782.
Wave propagation in graphene sheets with nonlocal elastic theory via finite element formulation. Computer Methods in Applied Mechanics and Engineering 223 (2012): 1-9.
Detection of gas atoms via vibration of graphenes. Physics Letters A 375.24 (2011): 2411-2415.
Postbuckling Analysis of Functionally Graded Cylindrical Shells
Postbuckling Analysis of Functionally Graded Cylindrical Shells
Buckling of circular cylindrical shells has posed baffling problems to engineering for many years. This is because large discrepancies between theoretical prediction and experimental results had been the focus of long debate in the case of compressive buckling of cylindrical shells. In this study, a postbuckling analysis is presented for a functionally graded cylindrical thin shell of finite length subjected to compressive axial loads and in thermal environments. Material properties are assumed to be temperature-dependent and graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents. The governing equations are based on the classical shell theory with von Kármán–Donnell-type of kinematic nonlinearity. The nonlinear prebuckling deformations and initial geometric imperfections of the shell are both considered. The effect of nonlinear prebuckling deformations, large deflections in the postbuckling range, and initial geometric imperfections of the shell, is extended to the case of functionally graded cylindrical shells.
Selected publication
Thermal buckling of multiwalled carbon nanotubes using a semi-analytical finite element approach. Journal of Thermal Stresses 34 (2011) 817-834.
Miscellaneous Simulation Studies
Miscellaneous Simulation Studies
Melting ice at room temperature and atmospheric pressure
When the ice starts melting, a slight disruption in the lattice first occurs inside the ice crystal. The disruption then expands along the plane. Melting occurs in the plane and expands rapidly over the whole system.
Wrapping a gene strand around a carbon nanotube
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