Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session A10: Polymer Nanocomposites - Mechanics |
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Sponsoring Units: DPOLY Chair: Laura Clarke, North Carolina State University Room: 269 |
Monday, March 13, 2017 8:00AM - 8:12AM |
A10.00001: Effect of Filler Morphology and Distribution State on the Nonlinear Mechanical Behaviour of Nanofilled Elastomers Didier Long, Mathieu Tauban, Paul Sotta, Jean-Yves Delannoy We study the response of elastomers filled with aggregates of different shapes, for deformations of various amplitudes. We show that the distribution state of the fillers controls the reinforcement at high temperature. Energy dissipation is not a monotonous function of the distribution state, exhibiting a maximum for intermediary distribution state. We show how the dynamics of yield of glassy bridges account for this non-monotonous dissipative behaviour. We also study the mechanical response of systems filled with well distributed aggregates of different morphologies. While the filler overall size is kept constant, we increase the number of constitutive primary particles to study aggregates made of one particle (spheres) up to 40 particles (fractal aggregate). Even if the distribution state is fixed, we show a strong effect of filler morphology on reinforcement. We show that distances between fillers are smaller with fractal aggregates leading to stronger reinforcement and non-linear effects. Our model opens the path for the development of systems with tailored properties by tuning the filler distribution state and morphology. [Preview Abstract] |
Monday, March 13, 2017 8:12AM - 8:24AM |
A10.00002: Coarse grained MD simulations of a fracture of filler-filled polymer nanocomposites under uniaxial elongation Katsumi Hagita, Hiroshi Morita, Hiroshi Takano We performed coarse grained molecular dynamics (MD) simulations based on Kremer-Grest model in order to investigate a fracture of polymer nanocomposites filled with spherical nanoparticles (NPs) under uniaxial elongation with a Poisson ratio of 0.4 [1]. In our model, the NP consists of 320 surface beads and one center bead. In order to make the NP spherical, a harmonic potential is applied to the surface particles from the center of the NP. Here, the initial volume fraction of the NPs is about 20{\%}. The dependences of the fracture on the interactions between the NPs and polymers were examined. In order to observe the creation of nanovoids, the interaction among the polymers was set to be attractive. When the NP-polymer interaction is attractive, nanovoids appear in the bulk of polymers. On the other hand, for repulsive NP-polymer interaction, nanovoids are created at the surface between the polymers and NPs. At the same time, segregation of NPs is observed. We found that these behaviors depend on crosslink densities. [1] K. Hagita, H. Morita, H. Takano, Polymer, 99, 368-375 (2016). [Preview Abstract] |
Monday, March 13, 2017 8:24AM - 8:36AM |
A10.00003: Controllable Reconfiguration of Polymer-grafted Nanoparticle Networks Under Torsion Tao Zhang, Badel Mbanga, Victor Yashin, Anna Balazs We use 3D computational modeling to study mechanically-induced changes in the structure of networks formed from polymer-grafted nanoparticles (PGNs). The nanoparticles’ rigid cores are decorated with a corona of grafted polymers, which contain reactive functional groups at the chain ends. With the overlap of the grafted polymers, these reactive groups can form labile bonds, which can reform after breakage. These PGN networks consist of two types of nanoparticles, which differ in the reactive functional groups at the chain ends. The energy of the labile bonds that are formed depends on the nature of these reactive groups. We demonstrate that the application of a rotational deformation results in a controllable reconfiguration of the network. Depending on the labile bond energies, the PGN networks are shown to exhibit a deformation-induced phase separation. The restructuring process can be controlled by boundary conditions. We can create complicated morphology such as spiral, with enhanced mechanical properties. Our results provide guidelines for designing mechano-mutable PGN-based materials whose nanoscale structures can be controllably changed under an applied mechanical action. [Preview Abstract] |
Monday, March 13, 2017 8:36AM - 8:48AM |
A10.00004: Similarity between the Damping Function and Payne Effect in Particle-Filled Elastomers Xiaorong Wang Recent research activities at Tongji have revealed that for many particle-filled rubbers their mechanical properties in step-shear and oscillatory-shear experiments display similar superposed rheological behavior in both linear and nonlinear regimes. The question addressed here are: does the damping function from the time-strain superposition take the same form as the Payne effect from the frequency-strain superposition does? Experimentally, both sets of data appear to be overlapping each other. If so, what would be the important implementation? [Preview Abstract] |
Monday, March 13, 2017 8:48AM - 9:00AM |
A10.00005: Abstract Withdrawn
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Monday, March 13, 2017 9:00AM - 9:12AM |
A10.00006: Self-healing fiber-reinforced composite Minwook Lee, Sam Yoon, Alexander Yarin In the present work two parts of the healing agent (commercially available epoxy resin and hardener) are encapsulated in separate polymeric nanofibers. The fibers are generated by a single-step dual coaxial solution blowing. The core-shell fibers with the diameters in the 200-2600 nm range are encased in the PDMS (polydimethyl siloxane) matrix to form a self-healing composite material. Under fatigue conditions, the core-shell fibers inside the composite material are ruptured and the healing agents released into the surrounding matrix. Various fatigue conditions including repeated bending and stretching are used to damage the composites and the degree of self-healing is quantified after that. Also, an incision resembling a crack is pre-notched and crack propagation is studied. It is found that the presence of the self-healing agents in the fibers significantly retards crack propagation due to curing by the epoxy at the ruptured site. The stiffness of the composites is also measured for the samples containing self-healing fibers inside them before and after the fatigue tests. A novel theory of crack propagation is proposed, which explains the observed jump-like growth of sub-critical cracks. [Preview Abstract] |
Monday, March 13, 2017 9:12AM - 9:24AM |
A10.00007: Thermomechanical properties and transparency of self-reinforced polylactide composites with stereocomplex polylactide nanofibers Naruki Kurokawa, Atsushi Hotta By compounding stereocomplex polylactide (sc-PLA) nanofibers into poly(L-lactide) (PLLA), we obtained an sc-PLA/PLLA composite with high transparency and sufficient mechanical properties. One of the major problems in the practical use of PLLA is its poor thermomechanical properties especially in the amorphous state: when heated, the storage modulus of pure PLLA drastically decreases through its glass transition temperature (T$_{\mathrm{g}}$\textasciitilde 68 degree). The fiber composite method could be an efficient way to solve the problem, while possibly avoiding marked reduction in its transparency. To maintain the high transparency of the original PLLA, the sc-PLA fiber diameter was optimized to be lower than the optical wavelength. In addition, to enhance the transparency, the reflective index should be closer and the sc-PLA fiber surface should be compatible with the PLLA matrix. Thus, the sc-PLA fibers of 367 nm in the average diameter were mixed with PLLA to improve its thermomechanical properties. At the sc-PLA nanofiber concentration of 15 weight percent, the storage modulus was increased by 21.8 times as compared with that of PLLA at 80 degree. It was also found that the transparency of PLLA did not drastically change after compounding. [Preview Abstract] |
Monday, March 13, 2017 9:24AM - 9:36AM |
A10.00008: Controllable polymer degradation via photothermal heating of embedded metal nanoparticles Honglu Huang, Russell E. Gorga, Daniela Fontecha, Gabriel Firestone, Jason R. Bochinski, Laura I. Clarke Polyethylene cyanoacrylate (PECA) is a thermally degradable polymer that can be fabricated at room temperature by controlled exposure of water or organic solvent to the monomer. When fabricated from residual water on the surface of starch, the resulting biodegradable composite has excellent tensile properties and well-defined thermal degradation that occurs above 180 °C. After one hour at 200 °C, degradation and evaporation of the volatile by-products result in removal of most of the PECA mass and complete loss of structural integrity. Neat PECA can also be formed at room temperature by mixing monomer with dimethylformamide (DMF) and then removing the residual DMF through heating, water exchange, or exposure to vacuum. In either case, dilute concentrations of metal nanoparticles can be incorporated within the material so that heat can be generated internally from the photothermal effect. In particular, when exposed to the light resonant with the embedded nanoparticle's localized surface plasmon resonance, the particles generate heat that can be utilized to either create mesoscopic voids within an otherwise intact sample or to explore novel degradation strategies. [Preview Abstract] |
Monday, March 13, 2017 9:36AM - 9:48AM |
A10.00009: Rheology as a mechano-scopic method to monitor growth of calcium carbonate in gelatin hydrogels Abigail U. Regitsky, Bavand Keshavarz, Gareth H. McKinley, Niels Holten-Andersen We have applied rheometry to study mineral nucleation and growth dynamics by measuring the modulations in viscoelastic mechanics of a hydrogel system during mineralization. Rheology is a superior tool to characterize mineral composite hydrogel mechanics and thereby mechano-scopically capture mineralization kinetics otherwise difficult to study using traditional microscopy techniques. Our system consists of a gelatin hydrogel matrix, which is preloaded with calcium ions, and an aqueous solution of carbonate ions, which are allowed to diffuse through the gel to initiate the mineralization process. We have found that gels with grown minerals exhibit higher storage and loss moduli than those without minerals and minerals simply mixed in. Specifically, they show a signature increase in low frequency energy dissipation, which scales with the volume fraction of particles mineralized in the matrix. We hypothesize that the distinct viscoelastic mechanics of the mineralized gels are caused by unique dissipative molecular dynamics at the CaCO$_{3}$-gelatin interface caused by polymer-particle incorporation. Lastly, we have mechano-scopically captured mineral growth in situ, showcasing the potential of rheology for studying mineralization kinetics in real time. [Preview Abstract] |
Monday, March 13, 2017 9:48AM - 10:00AM |
A10.00010: Multifunctional Polymer Nanocomposites. Alexandra Maria Galaska, Haixiang Song, Zhanhu Guo With more awareness of energy conversion/storage and saving, different strategies have been developed to utilize the sustainable and renewable energy. Introducing nanoscale fillers can make inert polymer matrix possess unique properties to satisfy certain functions. For example, alumina nanoparticles have strengthened the weak thermosetting polymers. A combined mixture of carbon nanofibers and magnetite nanoparticles have made the inert epoxy sensitive for magnetic field for sensing applications. Introducing silica nanoparticles into conductive polymers such as polyaniline has enhanced the giant magnetoresistance behaviors. The introduced nanoparticles have made the transparent polymer have the electromagnetic interference (EMI) shielding function while reduce the density significantly. With the desired miniaturization, the materials combining different functionalities have become importantly interesting. In this talk, methodologies to prepare nanocomposites and their effects on the produced nanocomposites will be discussed. A variety of advanced polymer nanocomposites will be introduced. Unique properties including mechanical, electrical, magnetoresistance etc. and the applications for environmental remediation, energy storage/saving, fire retardancy, electromagnetic interference shielding, and electronic devices will be presented. [Preview Abstract] |
Monday, March 13, 2017 10:00AM - 10:12AM |
A10.00011: Molecular Dynamics Simulation Of Novel Elastomer Nanocomposites: Structure Design And Property Prediction Jun Liu, Liqun Zhang In this talk, by employing molecular dynamics simulation, we aim to provide the structure design and property prediction of novel elastomer nanocomposites(ENCs), by considering three typical systems such as physical compounding, self-assembly and end-linked systems. We examine the dispersion, interfacial interaction and the resulting static and dynamic mechanical properties of each system. Emphasis is placed on how to tune the visco-elasticity and decrease the dynamic hysteresis loss of ENCs, by considering to introduce the flexible nanoparticles(NPs) with reversible mechanical deformation such as carbon nanosprings and graphene nanoribbon, or by achieving a homogeneous distribution of NPs in the elastomeric polymer matrix together with decreasing the mobility of the end-groups of polymer chains. In particular, the end-linked system exhibits both excellent static and dynamic mechanical properties, independent of the temperature. This novel ENCs could provide some useful guidances for the fabrication of high performance ENCs tailored for tire tread of green tires by cutting the fuel consumption. [Preview Abstract] |
Monday, March 13, 2017 10:12AM - 10:24AM |
A10.00012: Exploration of multifunctional properties of graphene nanoplatelet - epoxy composites reinforced by carbon fibers Richard Inakpenu, Maryam Jahan, Kuo Li, Guang-Lin Zhao We explored the multifunctional potential of graphene nanoplatelet (GNP) - epoxy composites reinforced with carbon fibers (CF) as new electromagnetic (EM) wave absorption and structural materials. The GNP loading was controlled from 3 to 7 wt.{\%} in the fabricated composite samples. We measured and analyzed the tensile strength, hardness, and the microwave (MW) absorption properties of the composites. The microwave measurements were done over a frequency range of 26.5 - 40 GHz in the R-band. The microwave absorption ratio of the composites strongly depends on the GNP loading in the material. A high MW absorption ratio up to 72{\%} was attained for the sample with 7 wt.{\%} GNP loading at high frequency \textasciitilde 40 GHz. The results of mechanical measurements show an increase in tensile strength with increased GNP loading in the composites. The tensile strength was increased from 85.9 $\pm$ 17.4 MPa for the sample without GNP, to 109.1 $\pm$ 7.9 MPa for GNP/CF/epoxy composite with 7 wt{\%} GNP loading. The improved tensile strength was due to the carbon fiber and GNP loading in the composite material. The hardness of the composites was also enhanced with GNP loading in the composites. The work was funded in part by ARO (Award {\#} W911NF-15-1-0483). [Preview Abstract] |
Monday, March 13, 2017 10:24AM - 10:36AM |
A10.00013: Polymeric CNT composites: atomistic simulations of interfacial properties Jacek Golebiowski, Arash A Mostofi, Peter D Haynes Functionalized carbon nanotube (FCNT)/polymer composites have received significant interest as promising structural materials with applications in the most demanding areas of industry such as ballistic protection. In order to optimise the properties of this class of materials, it is imperative to understand how load is transferred through the FCNT-polymer interface with the aim to identify the key factors determining the interfacial shear strength and dominant failure mechanisms. Computational investigation of the interface requires simulations of 10,000s of atoms in order to accurately describe the movement of polymer chains; however, critical interfacial failure involves changes in local chemistry such as bond-breaking effects, necessitating a quantum-mechanical (QM) treatment. These issues are addressed by employing a quantum/classical hybrid simulation technique `Learn on the Fly' [1]. In this approach, classical molecular dynamics is used to simulate the majority of the system under strain, while regions of particular interest where changes in electronic structure are likely to occur, are investigated using QM methods resulting in an accurate description of bond-breaking processes. \\~[1] G Cs\'{a}nyi, T Albaret, M C Payne, A De Vita, Phys. Rev. Let. 93(17):1–4, 2004 [Preview Abstract] |
Monday, March 13, 2017 10:36AM - 10:48AM |
A10.00014: Mechanical Properties of Graphene-Polymer Nanocomposites Asanka Weerasinghe, Dimitrios Maroudas, Ashwin Ramasubramaniam We report results from molecular-dynamics simulations of straining of polymer (high-density polyethylene) nanocomposites reinforced by graphene and fullerenes with the aim of elucidating the underlying mechanisms that govern the mechanical response of these composite materials. Using a united-atom-based model of the glassy polymer matrix, we show systematic trends in the enhancement of the mechanical stiffness of the composite as a function of filler concentration, size, and morphology, as well as matrix-filler interfacial interaction strength. From systematic studies of mechanical behavior, we find that the stiffness reinforcement is only weakly dependent on the filler size for fullerenes but shows an appreciable size dependence for graphene fillers. We explain the filler-size dependent elastic response of the graphene-reinforced polymer composites through detailed atomic-scale characterization in conjunction with a modified shear-lag continuum-mechanics model. In addition to capturing the nanocomposites' elastic response accurately, the modified shear-lag model also provides a quantitative estimate for a critical graphene flake size beyond which these 2D fillers can provide effective mechanical reinforcement through interfacial stress transfer. [Preview Abstract] |
Monday, March 13, 2017 10:48AM - 11:00AM |
A10.00015: Material Property Changes of Polycyanurate with Ionic Liquid and Carbon Nanotube Additives Evelyn Lopez, Devin M. Reed, Sindee L. Simon Cyanate ester monomers react to form crosslinked polycyanurate thermosetting polymers with excellent properties, including high glass transition temperatures, low dielectric loss, and good fracture toughness. To further optimize their mechanical properties, carbon nanotubes (CNs) are added to the di-functional cyanate ester monomer (DCE) and an imidazolium based ionic liquid (IL) is used as a mixing agent. Such techniques have been successfully applied in epoxy systems, however there is little data for cyanate esters, although their properties are comparable, and in some cases, better than, that of epoxy based systems. Here we use differential scanning calorimetry to measure the reaction rate kinetics and glass transition temperature (Tg) for three different systems: pure DCE, DCE + IL, and DCE + IL + CNs. The fracture toughness of the three systems will also be measured. Preliminary results show that the glass transition temperature decreases with the addition of ionic liquids, but the decrease is greater than that predicted by the rule of mixtures. [Preview Abstract] |
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