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Naghashpour A.,Concordia University at Montreal | Hoa S.V.,Center for Applied Research on Polymers and Composites
Composites Science and Technology | Year: 2013

The intention of the work presented in this paper was to find a way to measure the through-thickness strain (TTS) in composite laminates. The reason for this was because there did not seem to be any effective technique for the measurement of the TTS, particularly for locations away from the free edge. In the present work, Multiwalled carbon nanotubes (MWCNTs) were added into epoxy resin to make the resin electrically conductive. The modified resin was then incorporated with long glass fibers to make glass/epoxy laminates. The laminate was subjected to a uniaxial load, while the electrical resistances across the thickness of the laminate were measured. Two different types of uniaxial loads were applied. One was along the length of the sample and the other across the thickness of the sample. For the case where lengthwise load was applied, classical lamination theory (CLT) was used to calculate the average TTS (ATTS), and to find stacking sequences that can provide the largest ATTS for a certain load. Strain gage was mounted on the edge of the laminate in order to provide another means to measure the ATTS. It was found that the electrical resistance across the laminate thickness is sensitive to the axial load along the length of the sample. The magnitude of the change in electrical resistance across the laminate thickness is proportional to the strain measured by strain gage. However, while the strain measured by strain gage shows negative strain, there was an increase in the through-thickness electrical resistance (TTER). For the case of thicknesswise load, the strain is negative and the TTER shows decrease. For the thicknesswise load, the change in TTER can be related to the ATTS. For the lengthwise load, even though the magnitude of the change in TTER is proportional to the ATTS, the change in TTER may not be completely due to the ATTS. © 2013 Elsevier Ltd.

Dermanaki-Farahani R.,Ecole Polytechnique de Montreal | Lebel L.L.,Ecole Polytechnique de Montreal | Therriault D.,Center for Applied Research on Polymers and Composites
Journal of visualized experiments : JoVE | Year: 2014

Microstructured composite beams reinforced with complex three-dimensionally (3D) patterned nanocomposite microfilaments are fabricated via nanocomposite infiltration of 3D interconnected microfluidic networks. The manufacturing of the reinforced beams begins with the fabrication of microfluidic networks, which involves layer-by-layer deposition of fugitive ink filaments using a dispensing robot, filling the empty space between filaments using a low viscosity resin, curing the resin and finally removing the ink. Self-supported 3D structures with other geometries and many layers (e.g. a few hundreds layers) could be built using this method. The resulting tubular microfluidic networks are then infiltrated with thermosetting nanocomposite suspensions containing nanofillers (e.g. single-walled carbon nanotubes), and subsequently cured. The infiltration is done by applying a pressure gradient between two ends of the empty network (either by applying a vacuum or vacuum-assisted microinjection). Prior to the infiltration, the nanocomposite suspensions are prepared by dispersing nanofillers into polymer matrices using ultrasonication and three-roll mixing methods. The nanocomposites (i.e. materials infiltrated) are then solidified under UV exposure/heat cure, resulting in a 3D-reinforced composite structure. The technique presented here enables the design of functional nanocomposite macroscopic products for microengineering applications such as actuators and sensors.

Vu T.T.D.,Center for Applied Research on Polymers and Composites | Vu T.T.D.,Laval University | Mighri F.,Center for Applied Research on Polymers and Composites | Mighri F.,Laval University | And 3 more authors.
Journal of Nanoscience and Nanotechnology | Year: 2012

The present study presents the synthesis details of titanium dioxide (TiO 2) nanoparticles (NPs) of different morphologies using oleic acid (OA) and oleyl amine (OM) as capping agents. Different shapes of NPs, such as nanospheres, nanorods, and nanorhombics, were achieved. In order to develop nanocomposite thin films for photovoltaic cells, these TiO 2 NPs were carefully dispersed in 2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene (MEH-PPV) matrix. The properties of synthesized TiO 2 NPs and MEH-PPV/TiO 2 nanocomposites were characterized using transmission electron microscopy (TEM), thermogravimetric analysis (TGA), UV-Visible spectroscopy, and Photoluminescence technique. Obtained results showed promising properties for photovoltaic devices, especially solar radiation absorption properties and charge transfer at the interface of the conjugated MEH-PPV matrix and TiO 2 dispersed NPs. Copyright © 2012 American Scientific Publishers.

Patel J.D.,Center for Applied Research on Polymers and Composites | Patel J.D.,Laval University | Mighri F.,Center for Applied Research on Polymers and Composites | Mighri F.,Laval University | And 2 more authors.
Materials Research Bulletin | Year: 2012

This work deals with the synthesis of highly dispersed semiconducting nanocrystals (NCs) of cadmium sulphide (CdS), zinc sulphide (ZnS) and lead sulphide (PbS) through a simple and generalized process using oleic acid (OA) as surfactant. To synthesize these NCs, metal-oleate (M-O) complexes were obtained from the reaction at 140°C between metal acetates and OA in hexanes media. Subsequently, M-O complexes were sulphurized using thioacetamide at the same temperature. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) characterizations show that the synthesized products are of nanoscale-size with highly crystalline cubic phase. The optical absorption of OA-capped metal sulphide NCs confirms that their size quantization induced a large shift towards visible region. Photoluminescence (PL) spectrum of CdS NCs shows a broad band-edge emission with shallow and deep-trap emissions, while PL spectrum of ZnS NCs reveals a broad emission due to defects states on the surface. The thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy indicate that fatty acid monolayers were bound strongly on the nanocrystal surface as a carboxylate and the two oxygen atoms of the carboxylate were coordinated symmetrically to the surface of the NCs. The strong binding between the fatty acid and the NCs surface enhances the stability of NCs colloids. In general, this generalized route has a great potential in developing nanoscale metal sulphides for opto-electronic devices. © 2012 Elsevier Ltd. All rights reserved.

Patel J.D.,Center for Applied Research on Polymers and Composites | Patel J.D.,Laval University | Mighri F.,Center for Applied Research on Polymers and Composites | Mighri F.,Laval University | And 2 more authors.
Materials Letters | Year: 2012

In this work, we present for the first time a simple synthetic route to fabricate a controlled lead sulfide (PbS) structure using amino acid mixed precursor. High yield star-shaped PbS crystals were developed by solvothermal synthesis technique using an environment friendly aminocaproic acid (ACA) mixed methanolic Pb-TU complex precursor at 170 °C for 20 h. The mechanism leading to these star-shaped PbS crystals was discussed. The as-synthesized PbS crystals were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared (FTIR). The obtained results show that the synthesized star-shaped PbS crystals were exempt of impurities and were crystalline with cubic phase. Finally, the FTIR study indicates that molecules were bounded on the surface of PbS crystal via nitrogen lone pair of the amino head groups. © 2012 Elsevier B.V. All rights reserved.

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