Three-dimensional elastic constitutive relations of aligned carbon nanotube architectures

Handlin, Daniel; Stein, Itai Y.; Villoria, Roberto Guzmán de; Cebeci, Hülya; Parsons, Ethan M.; Socrate, Simona; Scotti, Stephen J.; Wardle, Brian L.

doi:10.1063/1.4842117

Cited by 29 publications

(55 citation statements)

References 40 publications

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“…These uncertainties in Γ min at V f ∼ 5% were estimated at ∼ ±10 − 15%, which lead to about the same order of magnitude of uncertainty in accessible porosity (see Figure 2c), as observed in the experimental data (see Figure 3b). Also, because previous studies on the capillary-assisted wetting of CNT arrays of varying V f with epoxy resins, which are less sensitive to moisture than phenolics, did not observe such an impact on infusion yield, [79][80][81][82] further studies on the interaction of the physisorbed water layers with introduced polymer species of varying chemistries is necessary. …”

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Exohedral Physisorption of Ambient Moisture Scales Non-monotonically with Fiber Proximity in Aligned Carbon Nanotube Arrays

et al. 2014

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Here we present a study on the presence of physisorbed water on the surface of aligned carbon nanotubes (CNTs) in ambient conditions, where the wet CNT array mass can be more than 200% larger than that of dry CNTs, and modeling indicates that a water layer > 5 nm thick can be present on the outer CNT surface. The experimentally observed non-linear and non-monotonic dependence of the mass of adsorbed water on the CNT packing (volume fraction) originates from two competing modes. Physisorbed water cannot be neglected in the design and fabrication of materials and devices using nanowires/nanofibers, especially CNTs, and further experimental and ab initio studies on the influence of defects on the surface energies of CNTs, and nanowires/nanofibers in general, are necessary to understand the underlying physics and chemistry that govern this system.One dimensional nanoscale systems, such as nanowires, nanofibers, and nanotubes, are well known for their phenomenal electrical, [1][2][3][4] thermal, [5][6][7][8] and mechanical properties, [9][10][11] which could enable the design and manufacture of next-generation materials with unprecedented properties. [12][13][14][15][16][17][18] However, while many studies have previously explored the synthesis of new architectures and devices using one dimensional nanomaterials, specifically carbon nanotubes (CNTs), the properties they reported were far lower than the properties of predicted using current theory.[12] Some of the main reasons why existing models cannot accurately predict the behavior of CNTs in scalable architectures, such as aligned CNT arrays, are the various CNT morphology and proximity effects, [13][14][15]19] which can strongly impact properties, but are not well understood and cannot be properly integrated into theoretical frameworks. Here we report the presence of a commonly neglected morphological effect, an unexpectedly large (compared to the CNT mass) amount of moisture located on the surface of CNTs in aligned CNT (A-CNT) arrays at ambient conditions; show the non-linear and non-monotonic dependence of this effect on array porosity, which suggests two competing mechanisms; and discuss the strong impact such an effect can have on the structure and properties of nanocomposite architectures composed of A-CNTs.Previous studies on how water interacts with the outer surface of a CNT illustrated that the water molecules form a layer-like shell surrounding the CNTs, [20][21][22][23] and that the water layer density varies greatly and non- * wardle@mit.edu.monotonically with its thickness. [21,22] A recent study on the physisorption of water onto the external surface of a suspended ∼ 1.1 − 1.2 nm diameter single walled CNT showed that more than one layer of water is present on the CNT surface in water vapor, and that water molecules more easily adsorb onto larger diameter CNTs.[24] However, this study was limited to isolated and defect-free CNTs, [24,25] meaning that the interaction of moisture present in ambient air with multiwalled CNTs, which normally have nativ...

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Exohedral Physisorption of Ambient Moisture Scales Non-monotonically with Fiber Proximity in Aligned Carbon Nanotube Arrays

et al. 2014

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“…12 To utilize the exceptional and highly anisotropic intrinsic properties of NFs in material solutions, many recent studied focused on the use of aligned NF arrays, especially aligned carbon nanotubes (A-CNTs), in nanocomposite structures, specifically aligned CNT polymer matrix nanocomposites (A-PNCs). [18][19][20][21][22][23][24][25][26][27][28] However, the properties reported by these previous works did not live up to the behavior predicted using current theoretical frameworks. 12 Some of the main reasons why existing models cannot accurately predict the behavior of A-CNTs architectures, such as A-CNT arrays, are the various CNT morphology and proximity effects, 13,14,18,29 which can strongly impact properties, 27,30,31 but are not well understood and cannot be adequately described in current-generation theoretical frameworks.…”

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confidence: 72%

“…Also, previous work on A-PNCs has shown that CNT waviness could lead to composite moduli that are > 10× lower than the ones predicted by rule of mixtures analysis of collimated CNTs, 26,34 and that the waviness of the CNTs can be reduced by CNT packing proximity, normally quantified by an increase in the CNT volume fraction (V f ). 26,58 However, current-generation theoretical and numerical models cannot account for an evolving waviness ratio (w), and can only describe the CNT waviness using simple functional forms, e.g. sinusoidal or helical functional forms.…”

Section: Nomenclaturementioning

confidence: 99%

“…27 In this work, a previously reported simulation framework capable of simulating 10 5 CNTs with stochastic waviness, 27,31,60 and representative scaling of w with with V f , is used to evaluate the scaling of the intrinsic CNT elastic modulus (E cnt ) with w. 27,31 This is achieved by studying the contribution of (axial) stretching, (radial) shear, and bending on the deformation of CNTs in the A-PNC using an analysis similar to applied to study wavy CNTs, 31 which originates from early work on the mechanical behavior of carbon nanocoils. 61 In conjunction with recent experimental data on an exemplary A-PNC system, 26 these results are used to compare the predicted scaling of the A-PNC elastic modulusp (E pnc ) with V f for the current scheme with the results of a previous finite element analysis (FEA) to show that more complete descriptions of the CNT morphology can lead to more accurate material property prediction. This report draws heavily from very recent studies on the mechanical behavior of wavy A-CNT (Ref.…”

Section: Nomenclaturementioning

confidence: 99%

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Influence of Waviness on the Elastic Properties of Aligned Carbon Nanotube Polymer Matrix Nanocomposites

Stein

Wardle

2016

57th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

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The promise of enhanced performance has motivated the study of one dimensional nanomaterials, especially aligned carbon nanotubes (A-CNTs), for the reinforcement of polymeric materials. While early work has shown that CNTs have remarkable theoretical properties, more recent work on aligned CNT polymer matrix nanocomposites (A-PNCs) have reported mechanical properties that are orders of magnitude lower than those predicted by rule of mixtures. This large difference primarily originates from the morphology of the CNTs that reinforce the A-PNCs, which have significant local curvature commonly referred to as waviness, but are commonly modeled using the oversimplified straight column geometry. Here we used a simulation framework capable of analyzing 10 5 wavy CNTs with realistic stochastic morphologies to study the influence of waviness on the compliance contribution of wavy A-CNTs to the effective elastic modulus of A-PNCs, and show that waviness is responsible for the orders of magnitude over-prediction of the A-PNC effective modulus by existing theoretical frameworks that both neglect the shear deformation mechanism and do not properly account for the CNT morphpology. Additional work to quantify the morphology of A-PNCs in three dimensions and simulate their full elastic constitutive relations is planned.

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“…Indeed, an A-PNC is a representative volume element in such nanoengineered FRP composites. Here, we focus on the prediction of A-PNC elastic properties based on constituent properties using a combined molecular dynamics and finite-element approach, looking towards experiment-model correlation with regard to experimental work [13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics and Finite Element Investigation of Polymer Interphase Effects on Effective Stiffness of Wavy Aligned Carbon Nanotube Composites

Atescan

Hadden

Wardle

et al. 2015

56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

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Interphase effects have been studied for their effect on composite properties for many decades, and it is well documented that an interphase can exist in polymer composites comprised of nanofibers as well. We present a first study of interphase effects on the basic elastic response of wavy aligned carbon nanotube (A-CNT) polymer nanocomposties (PNCs). Waviness is characterized by ex situ pre-fabrication imaging of A-CNT forests and used as an input to finite element analyses of the PNCs containing an interphase region in the thermoset polymer defined using molecular dynamics (MD) simulations. The interphase thickness of ~1nm is found to be independent of crosslink density and contain regions of both higher and lower mass density than the bulk polymer. Finite element analyses of wavy single and double-wall A-CNT PNCs incorporating this interphase, allow the effective stiffness based on a representative volume element to be calculated. Waviness of the A-CNTs dominates the effective axial stiffness of the PNCs, with the interphase having a negligible effect. The interphase changes the stress and strain distribution local to the CNT 'fiber' and this is expected to play an important role in failure, such as CNT pullout, of the CNTpolymer system. These findings, in addition to the relatively high volume fraction (V f ) of the interphase in PNCs with high CNT V f , suggests that the interphase may play a more important role in PNCs than in micron-scale (typical) collimated fiber composites. Future work in this area includes inelastic polymer response during nanofiber pullout. Nomenclature A = waviness amplitude of CNT A-PNC = aligned-CNT polymer nanocomposite Case-A = DWCNT outer wall contribution to stiffness Case-B = DWCNT all walls contribution to stiffness CNT = carbon nanotube CFRP = carbon fiber reinforced plastic DWCNT = double walled carbon nanotube d i = inner diameter of CNT d o = outer diameter of CNT 2 E RVE = axial modulus of representative volume element E w = wall modulus FEA = finite element analysis FRP = filament fiber reinforced plastic HR-SEM = high resolution scanning electron microscope L = length of wavy CNT MD = molecular dynamics PNC = polymer nanocomposite RVE = representative volume element SWCNT = single walled carbon nanotube t w = wall thickness w = waviness ratio of CNT

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Three-dimensional elastic constitutive relations of aligned carbon nanotube architectures

Cited by 29 publications

References 40 publications

Exohedral Physisorption of Ambient Moisture Scales Non-monotonically with Fiber Proximity in Aligned Carbon Nanotube Arrays

Exohedral Physisorption of Ambient Moisture Scales Non-monotonically with Fiber Proximity in Aligned Carbon Nanotube Arrays

Influence of Waviness on the Elastic Properties of Aligned Carbon Nanotube Polymer Matrix Nanocomposites

Molecular Dynamics and Finite Element Investigation of Polymer Interphase Effects on Effective Stiffness of Wavy Aligned Carbon Nanotube Composites

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