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Jonghwan Suhr

Bio: Jonghwan Suhr is an academic researcher from University of Delaware. The author has contributed to research in topics: Materials science & Carbon nanotube. The author has an hindex of 20, co-authored 49 publications receiving 2979 citations. Previous affiliations of Jonghwan Suhr include University of Nevada, Reno & Sungkyunkwan University.


Papers
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Journal ArticleDOI
TL;DR: In this article, the authors reviewed relevant literature which deals with various manifestations of energy absorption of composites from the nano to the macro-scale, with emphasis on the nano-scale.

472 citations

Journal ArticleDOI
TL;DR: Direct shear testing of epoxy thin films containing dense packing of multiwalled carbon nanotube fillers and report strong viscoelastic behaviour with up to 1,400% increase in loss factor (damping ratio) of the baseline epoxy, concluding that damping is related to frictional energy dissipation during interfacial sliding at the large, spatially distributed, nanotubes–nanotube interfaces.
Abstract: Polymer composites reinforced by carbon nanotubes have been extensively researched for their strength and stiffness properties. Unless the interface is carefully engineered, poor load transfer between nanotubes (in bundles) and between nanotubes and surrounding polymer chains may result in interfacial slippage and reduced performance. Interfacial shear, although detrimental to high stiffness and strength, could result in very high mechanical damping, which is an important attribute in many commercial applications. We previously reported evidence of damping in nanocomposites by measuring the modal response (at resonance) of cantilevered beams with embedded nanocomposite films. Here we carry out direct shear testing of epoxy thin films containing dense packing of multiwalled carbon nanotube fillers and report strong viscoelastic behaviour with up to 1,400% increase in loss factor (damping ratio) of the baseline epoxy. The great improvement in damping was achieved without sacrificing the mechanical strength and stiffness of the polymer, and with minimal weight penalty. Based on the interfacial shear stress (approximately 0.5 MPa) at which the loss modulus increases sharply for our system, we conclude that the damping is related to frictional energy dissipation during interfacial sliding at the large, spatially distributed, nanotube-nanotube interfaces.

459 citations

Journal ArticleDOI
Lijie Ci1, Jonghwan Suhr1, V. Pushparaj1, Xiao Zhang1, Pulickel M. Ajayan1 
TL;DR: Under compressive loadings, the nanotube composites can generate more than an order of magnitude improvement in the longitudinal modulus ( up to 3,300%) as well as damping capability (up to 2,100%).
Abstract: Carbon nanotubes are considered short fibers, and polymer composites with nanotube fillers are always analogues of random, short fiber composites. The real structural carbon fiber composites, on the other hand, always contain carbon fiber reinforcements where fibers run continuously through the composite matrix. With the recent optimization in aligned nanotube growth, samples of nanotubes in macroscopic lengths have become available, and this allows the creation of composites that are similar to the continuous fiber composites with individual nanotubes running continuously through the composite body. This allows the proper utilization of the extreme high modulus and strength predicted for nanotubes in structural composites. Here, we fabricate such continuous nanotube polymer composites with continuous nanotube reinforcements and report that under compressive loadings, the nanotube composites can generate more than an order of magnitude improvement in the longitudinal modulus (up to 3300%) as well as dampi...

320 citations

Journal ArticleDOI
TL;DR: It is shown that under repeated high compressive strains, long, vertically aligned multiwalled nanotubes exhibit viscoelastic behaviour similar to that observed in soft-tissue membranes, and that their good electrical conductivity could lead to their use as compliant electrical contacts in a variety of applications.
Abstract: Structural components subject to cyclic stress can succumb to fatigue, causing them to fail at stress levels much lower than if they were under static mechanical loading1 However, despite extensive research into the mechanical properties of carbon nanotube structures2,3,4,5,6,7,8,9 for more than a decade, data on the fatigue behaviour of such devices have never been reported We show that under repeated high compressive strains, long, vertically aligned multiwalled nanotubes exhibit viscoelastic behaviour similar to that observed in soft-tissue membranes10,11 Under compressive cyclic loading, the mechanical response of the nanotube arrays shows preconditioning, characteristic viscoelasticity-induced hysteresis, nonlinear elasticity and stress relaxation, and large deformations Furthermore, no fatigue failure is observed at high strain amplitudes up to half a million cycles This combination of soft-tissue-like behaviour and outstanding fatigue resistance suggests that properly engineered nanotube structures could mimic artificial tissues, and that their good electrical conductivity could lead to their use as compliant electrical contacts in a variety of applications

289 citations

Journal ArticleDOI
26 Aug 2014-ACS Nano
TL;DR: This work demonstrates the implementation of a laminated ultrathin CVD graphene film as a stretchable and transparent electrode for supercapacitors and demonstrates excellent frequency capability with small time constants under stretching.
Abstract: Due to their exceptional flexibility and transparency, CVD graphene films have been regarded as an ideal replacement of indium tin oxide for transparent electrodes, especially in applications where electronic devices may be subjected to large tensile strain. However, the search for a desirable combination of stretchability and electrochemical performance of such devices remains a huge challenge. Here, we demonstrate the implementation of a laminated ultrathin CVD graphene film as a stretchable and transparent electrode for supercapacitors. Transferred and buckled on PDMS substrates by a prestraininig-then-buckling strategy, the four-layer graphene film maintained its outstanding quality, as evidenced by Raman spectra. Optical transmittance of up to 72.9% at a wavelength of 550 nm and stretchability of 40% were achieved. As the tensile strain increased up to 40%, the specific capacitance showed no degradation and even increased slightly. Furthermore, the supercapacitor demonstrated excellent frequency capa...

233 citations


Cited by
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Journal ArticleDOI
01 Feb 2013-Science
TL;DR: Although not yet providing compelling mechanical strength or electrical or thermal conductivities for many applications, CNT yarns and sheets already have promising performance for applications including supercapacitors, actuators, and lightweight electromagnetic shields.
Abstract: Worldwide commercial interest in carbon nanotubes (CNTs) is reflected in a production capacity that presently exceeds several thousand tons per year. Currently, bulk CNT powders are incorporated in diverse commercial products ranging from rechargeable batteries, automotive parts, and sporting goods to boat hulls and water filters. Advances in CNT synthesis, purification, and chemical modification are enabling integration of CNTs in thin-film electronics and large-area coatings. Although not yet providing compelling mechanical strength or electrical or thermal conductivities for many applications, CNT yarns and sheets already have promising performance for applications including supercapacitors, actuators, and lightweight electromagnetic shields.

4,596 citations

Journal ArticleDOI
TL;DR: Department of Materials Science, University of Patras, Greece, Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, and Dipartimento di Scienze Farmaceutiche, Universita di Trieste, Piazzale Europa 1, 34127 Triesteadays.
Abstract: Department of Materials Science, University of Patras, 26504 Rio Patras, Greece, Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vass. Constantinou Avenue, 116 35 Athens, Greece, Institut de Biologie Moleculaire et Cellulaire, UPR9021 CNRS, Immunologie et Chimie Therapeutiques, 67084 Strasbourg, France, and Dipartimento di Scienze Farmaceutiche, Universita di Trieste, Piazzale Europa 1, 34127 Trieste, Italy

3,886 citations

Journal ArticleDOI
TL;DR: In this paper, a review of the current understanding of carbon nanotubes and CNT/polymer nanocomposites with two particular topics: (i) the principles and techniques for CNT dispersion and functionalization and (ii) the effects of CNT-based functionalization on the properties of polymers.
Abstract: Carbon nanotubes (CNTs) hold the promise of delivering exceptional mechanical properties and multi-functional characteristics. Ever-increasing interest in applying CNTs in many different fields has led to continued efforts to develop dispersion and functionalization techniques. To employ CNTs as effective reinforcement in polymer nanocomposites, proper dispersion and appropriate interfacial adhesion between the CNTs and polymer matrix have to be guaranteed. This paper reviews the current understanding of CNTs and CNT/polymer nanocomposites with two particular topics: (i) the principles and techniques for CNT dispersion and functionalization and (ii) the effects of CNT dispersion and functionalization on the properties of CNT/polymer nanocomposites. The fabrication techniques and potential applications of CNT/polymer nanocomposites are also highlighted.

2,849 citations

Journal ArticleDOI
TL;DR: The nanocomposite nature of the extracellular matrix is reviewed, the design considerations for different tissues are described, and the impact of nanostructures on the properties of scaffolds and their uses in monitoring the behaviour of engineered tissues are discussed.
Abstract: Tissue engineering aims at developing functional substitutes for damaged tissues and organs. Before transplantation, cells are generally seeded on biomaterial scaffolds that recapitulate the extracellular matrix and provide cells with information that is important for tissue development. Here we review the nanocomposite nature of the extracellular matrix, describe the design considerations for different tissues and discuss the impact of nanostructures on the properties of scaffolds and their uses in monitoring the behaviour of engineered tissues. We also examine the different nanodevices used to trigger certain processes for tissue development, and offer our view on the principal challenges and prospects of applying nanotechnology in tissue engineering.

1,272 citations

Journal ArticleDOI
TL;DR: The resulting graphene aerogels with density as low as 3 mg cm(-3) show excellent resilience and can completely recover after more than 90% compression.
Abstract: Chemically converted graphene aerogels with ultralight density and high compressibility are prepared by diamine-mediated functionalization and assembly, followed by microwave irradiation. The resulting graphene aerogels with density as low as 3 mg cm(-3) show excellent resilience and can completely recover after more than 90% compression. The ultralight graphene aerogels possessing high elasticity are promising as compliant and energy-absorbing materials.

1,225 citations