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Dermanaki-Farahani R.,Ecole Polytechnique de Montréal | Lebel L.L.,Ecole Polytechnique de Montréal | 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.


Naghashpour A.,Concordia University at Montréal | Naghashpour A.,Center for Applied Research on Polymers and Composites | Van Hoa S.,Concordia University at Montréal | Van Hoa S.,Center for Applied Research on Polymers and Composites
Structural Health Monitoring | Year: 2015

A significant safety concern preventing extensive use of composite materials for large polymer composite structures is the ability to detect, locate, and quantify damages that occur at one or several locations in large polymer composite structures. Real-time health monitoring of large polymer composite structures improves their performance, durability, and reliability while minimizing the life cycle cost. In this article, we present a new, practical, and real-time structural health monitoring technique for detecting, locating, and quantifying damages in large polymer composite structures made of carbon fibers and carbon nanotube networks. In this technique, electrically conductive epoxy resin was prepared by dispersing multiwalled carbon nanotubes into epoxy matrix. This modified epoxy matrix was then incorporated with long carbon fibers to make large composite plates. Two sets of grid points made from silver-epoxy paste were mounted on the surface of the large plates. The first set was used to apply the constant electric current, and the second set was utilized to measure the electric potential. The electric potentials across the second set of grid points on the undamaged plate were measured and used as a reference set. Two different damages were created by drilling holes and by applying impact loading on the large plates. It is found that the electric potential between the contact points surrounding the damage changes. The significant change in electric potential corresponds to the damage location in the plates. As such, drilled holes, impact damages, and barely visible impact damages are detected, located, and quantified. © The Author(s) 2014.


Naghashpour A.,Concordia University at Montréal | 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.


Nguyen L.,Center for Applied Research on Polymers and Composites | Nguyen L.,Laval University | Mighri F.,Center for Applied Research on Polymers and Composites | Mighri F.,Laval University | And 4 more authors.
Fuel Cells | Year: 2010

The aim of this work was to develop and characterise electrically conductive materials for proton exchange membrane fuel cells and bipolar plates (BPPs). These BPPs were made from highly conductive blends of polyethylene terephthalate (PET) and polyvinylidene fluoride (PVDF), as matrix phase. The conductive materials were developed from carefully formulated blends composed of conductive carbon black (CB) powder and, in some cases, graphite synthetic flakes mixed with pure PET, PVDF or with PVDF/PET systems. They were first developed by twin-screw extrusion process then compression-molded to give BPP final shape. As the developed blends have to meet properties suitable for BPP applications, they were characterised for their rheological properties, electrical through-plane resistivity (the inverse of conductivity), oxygen permeability, flexural and impact properties. Results showed that lower resistivity was obtained with PVDF/CB blends due to the higher interfacial energy between the PVDF matrix and CB and also the higher density and crystallinity of PVDF, compared to those of PET. It was also observed that the lowest resistivity values were obtained with mixing PVDF and PET at controlled compositions to ensure PVDF/PET co-continuous morphology. Also, slow cooling rates helped to attain the lowest values of through-plane resistivity for all studied blends. This behaviour was related to the higher crystallinity obtained with low cooling rates leading to smaller amorphous regions in which carbon particles are much more concentrated. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Mohiuddin M.,Concordia University at Montréal | Mohiuddin M.,Center for Applied Research on Polymers and Composites | Hoa S.V.,Concordia University at Montréal | Hoa S.V.,Center for Applied Research on Polymers and Composites
Composites Science and Technology | Year: 2011

The effect of temperature on electrical conductivity of nanocomposites consisting of Chemical Vapor Deposition (CVD)-grown multi-walled Carbon Nanotube (MWCNT) and Poly Ether Ether Ketone (PEEK) is presented in this paper. Different weight percentages of carbon nanotubes (CNT) were dispersed in PEEK through shear mixing by calendaring technique in Brabender. Percolation limit of the system was measured and discussed. The resulting nanocomposites were molded into round shaped pieces of 25.4. mm diameter and 1.4. mm thickness. The samples were then heated from room temperature to 140 °C while electrical conductivity is measured. It is found that electrical conductivity increases significantly with the increase in temperature and the rate of increase in conductivity with temperature depends on the content of CNT. The change in electrical conductivity does not follow the same route for heating and cooling cycle, thus resulting in electrical hysteresis. © 2011 Elsevier Ltd.


Naghashpour A.,Concordia University at Montréal | Naghashpour A.,Center for Applied Research on Polymers and Composites | Van Hoa S.,Concordia University at Montréal | Van Hoa S.,Center for Applied Research on Polymers and Composites
Polymer Testing | Year: 2016

Interesting behavior is observed in the electrical resistance across the thickness of glass fibers/epoxy/carbon nanotubes (CNTs) laminate when the laminate is subjected to uniaxial stress along its length. Normally, when a tensile stress is applied along the length of the laminate, Poisson coupling would result in a decrease in the thickness of the laminate. One may expect that this would give rise to smaller electrical resistance across the thickness of the laminate due to the smaller dimension. However, the opposite is observed, ie., an increase in electrical resistance across the thickness. Additional experiments with loading along different directions were imposed on the laminate and electrical resistance was measured. An explanation is provided for this behavior. The results from these simple experiments and the proposed explanation can provide insight into the effect of the motion of the nanostructure on the macro electrical resistance behavior of polymer composite structures containing CNTs when the structure is subjected to multi-directional deformation. © 2016 Elsevier Ltd


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 3 more authors.
Materials Chemistry and Physics | Year: 2012

In this study, lead sulphide (PbS) particles were synthesized from methanolic lead acetate-thiourea (PbAc-TU) complex via various precipitation techniques based on the decomposition of methanolic PbAc-TU complex. The influence of these techniques on the morphology, size and physical properties of PbS particles was studied in details. In general, scanning electron microscopy of the PbS particles produced by conventional chemical bath deposition, sonochemical bath deposition and microwave-assisted chemical bath deposition revealed that they were nanostructured with different size and shape. X-ray diffraction confirmed their high purity, while X-ray photoelectron spectroscopy (XPS) showed that they were partially oxidized due to their high surface energy. Optical absorption, transmission electron microscopy, selective area electron diffraction and XPS of capped nanoparticles (NPs) produced via capping assisted chemical bath deposition using poly(vinyl-pyrrolidone) (PVP) and oleic acid (OA) indicated that narrow size distributed PbS NPs absorbed strongly in the visible region with cubic crystalline phase without any evidence of surface oxidation. Fourier transform infrared spectroscopy of PVP-capped PbS NPs showed strong interaction between PbS NPs and polymer matrix, while for OA-capped PbS NPs, OA was chemically absorbed on the surface of PbS NPs. © 2011 Elsevier B.V. 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 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.


Song J.,Laval University | Song J.,Nanjing University of Technology | Mighri F.,Laval University | Mighri F.,Center for Applied Research on Polymers and Composites | And 3 more authors.
Polymer Engineering and Science | Year: 2012

Polyvinylidene fluoride/poly(ethylene terephthalate) (PVDF/PET)-based composites for proton exchange membrane fuel cell bipolar plates (BPs) were prepared at different crystallization temperatures and characterized by X-ray diffraction, differential scanning calorimetry, and resistivity setup. Composite conductivity was made possible by using a mixture of carbon black (CB) and graphite (GR). To improve composite processability, its viscosity was reduced by adding a small amount of cyclic butylene terephthalate (c-BT) oligomer and thermoplastic polyolefin elastomer. In the PVDF/PET-based composite, it was found that PVDF phase could crystallize easily but PET crystallization was difficult. Because of the CB/GR additives, the formed crystals in PVDF/PET phases had a poor perfection degree and showed a lower melting temperature when compared with pure PVDF and PET. It was observed that PET nucleation was accelerated but not that of PVDF. According to through-plane resistivity results, composite crystallization temperature range was divided into two parts (below/above 170°C), in which a different variation behavior of through-plane resistivity was observed. It has been proved that the resistivity was mainly governed by the network of CB/GR developed inside the PET phase, and decreasing the crystallinity of PET led to a decrease of through-plane resistivity, which is desirable for BPs. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers Copyright © 2012 Society of Plastics Engineers.

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