Browsing by Author "Al-Haik, Marwan S."

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    Enhanced vibration damping of carbon fibers-ZnO nanorods hybrid composites
    Skandani, Amir A.; Masghouni, N.; Case, Scott W.; Leo, D. J.; Al-Haik, Marwan S. (AIP Publishing, 2012-08-01)
    In this study, ZnO nanorods are grown on the surface of polyacrylonitrile based carbon fibers using a low temperature hydrothermal synthesis technique. Bi-layered carbon fiber-ZnO nanorod hybrid composite with epoxy matrix is prepared and tested for vibrational attenuations using dynamic mechanical analysis. Results revealed that the growth of ZnO nanorods on top of carbon fiber increases the damping performance by 50% while causing a slight decrease (similar to 7%) on the storage modulus. The enhanced damping of the hybrid composites can be related to the frictional mechanisms between the ZnO nanorod/epoxy and nanorod/nanorod interfaces combined with piezoelectric effect of ZnO. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4746398]
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    Hybrid Composites Based on Carbon Fiber/Carbon Nanofilament Reinforcement
    Tehrani, Mehran; Yari Boroujeni, Ayoub; Luhrs, Claudia; Phillips, Jonathan; Al-Haik, Marwan S. (MDPI, 2014-05-28)
    Carbon nanofilament and nanotubes (CNTs) have shown promise for enhancing the mechanical properties of fiber-reinforced composites (FRPs) and imparting multi-functionalities to them. While direct mixing of carbon nanofilaments with the polymer matrix in FRPs has several drawbacks, a high volume of uniform nanofilaments can be directly grown on fiber surfaces prior to composite fabrication. This study demonstrates the ability to create carbon nanofilaments on the surface of carbon fibers employing a synthesis method, graphitic structures by design (GSD), in which carbon structures are grown from fuel mixtures using nickel particles as the catalyst. The synthesis technique is proven feasible to grow nanofilament structures—from ethylene mixtures at 550 °C—on commercial polyacrylonitrile (PAN)-based carbon fibers. Raman spectroscopy and electron microscopy were employed to characterize the surface-grown carbon species. For comparison purposes, a catalytic chemical vapor deposition (CCVD) technique was also utilized to grow multiwall CNTs (MWCNTs) on carbon fiber yarns. The mechanical characterization showed that composites using the GSD-grown carbon nanofilaments outperform those using the CCVD-grown CNTs in terms of stiffness and tensile strength. The results suggest that further optimization of the GSD growth time, patterning and thermal shield coating of the carbon fibers is required to fully materialize the potential benefits of the GSD technique.
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    A modified strong-contrast expansion for estimating the effective thermal conductivity of multiphase heterogeneous materials
    Safdari, Masoud; Baniassadi, Majid; Garmestani, Hamid; Al-Haik, Marwan S. (American Institute of Physics, 2012-12-01)
    To evaluate the effective thermal conductivity of a general anisotropic multiphase microstructure, a modified version of statistical strong-contrast expansions is formulated here. The proposed method takes into account the shape, orientation, and distribution of each phase through two-point and three-point correlation functions. By applying a recently developed method, three-point correlation functions are approximated from the two-point correlation functions. Numerically, it is shown that for high contrast constituents, the solution of the third-order strong-contrast expansions is very sensitive to the selection of the reference medium. A technique is proposed to minimize the sensitivity of the solution. To establish the validity of the methods developed, the effective thermal conductivity of a number of isotropic and anisotropic two-phase and three-phase microstructures is evaluated and compared to their corresponding finite element (FE) simulations. Good agreement between the FE simulations and the proposed method predictions in the cases studied confirms its validity. When there are orders of magnitude disparity between the properties of the constituents, the developed method can be applied to better estimate the effective thermal conductivity of the multiphase heterogeneous materials in comparison with previous strong contrast model and other homogeneous methods. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4768467]
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    Patterning the Stiffness of Elastomeric Nanocomposites by Magnetophoretic Control of Cross-linking Impeder Distribution
    Ghosh, Suvojit; Tehrani, Mehran; Al-Haik, Marwan S.; Puri, Ishwar K. (MDPI, 2015-01-30)
    We report a novel method to pattern the stiffness of an elastomeric nanocomposite by selectively impeding the cross-linking reactions at desired locations while curing. This is accomplished by using a magnetic field to enforce a desired concentration distribution of colloidal magnetite nanoparticles (MNPs) in the liquid precursor of polydimethysiloxane (PDMS) elastomer. MNPs impede the cross-linking of PDMS; when they are dispersed in liquid PDMS, the cured elastomer exhibits lower stiffness in portions containing a higher nanoparticle concentration. Consequently, a desired stiffness pattern is produced by selecting the required magnetic field distribution a priori. Up to 200% variation in the reduced modulus is observed over a 2 mm length, and gradients of up to 12.6 MPa·mm−1 are obtained. This is a significant improvement over conventional nanocomposite systems where only small unidirectional variations can be achieved by varying nanoparticle concentration. The method has promising prospects in additive manufacturing; it can be integrated with existing systems thereby adding the capability to produce microscale heterogeneities in mechanical properties.
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    Reciprocal effects of the chirality and the surface functionalization on the drug delivery permissibility of carbon nanotubes
    Skandani, Amir A.; Al-Haik, Marwan S. (The Royal Society of Chemistry, 2013-10-24)
    The drug delivery admissibility of nanomaterials such as carbon nanotubes and their uncertain interactions with live tissues and organs have sparked ongoing research efforts. To boost the selective diffusivity of single walled carbon nanotubes (SWCNTs), surface functionalization was adopted in several experimental attempts. Numerous studies had identified polyethylene glycol (PEG) as a bio-compatible surfactant to carbon nanotubes. In this study, a large scale, atomistic molecular dynamic simulation was utilized to disclose the cellular exposure and uptake mechanisms of PEG-functionalized single walled carbon nanotubes (f-SWCNTs) into a lipid bilayer cell membrane. Results showed that with PEGs attached to a SWCNT, the penetration depth and speed can be controlled. Also, the simulations revealed that the adhesion energy between the nanotube and the lipid membrane is affected considerably, in the presence of PEGs, by the chirality of the SWCNTs.