Fig. 1: Four point probe measurements under tensile loading conditions. (All dimensions are in mm) 10 4 Electro-Mechanical Response of Carbon Nanotube Reinforced Polymer Composites Venkat K. Vadlamani1, Vijaya B. Chalivendra1*, Arun Shukla2, Sze Yang2 1University of Massachusetts, North Dartmouth, MA 02747, USA 2University of Rhode Island, Kingston, RI, 02881, USA * Corresponding author, vchalivendra@umassd.edu, 508-910-6572 ABSTRACT The effect of nano-deformation, damage and growth of carbon nanotubes (CNTs) reinforced polymer composites is investigated using electro-mechanical response at different loading conditions. Three different polymer systems namely polyurethane, polyurethane reinforced with gas bubbles (that induces porosity) and polyurethane reinforced with Aluminum Silicate hollow microspheres (Cenospheres) in this study. CNTs of different weight percentages are loaded into above three polymer systems and a combination of shear mixing and ultrasonication processes are used to fabricate composites. High-resolution scanning electron microscopy and transmission electron microscopy are used to verify homogenous dispersion of CNTs in the above systems. A four-point probe method is used to measure high resolution electrical response when the above polymer systems are subjected to mechanical loads. The effect of various types of mechanical loading on different stages of deformation of test samples, onset of damage and growth will be discussed using electro-mechanical response of polymer systems. 1. Introduction Due to their high electrical conductivity, carbon nanotubes are used as sensory network in polymers to understand their deformation and damage in the materials. Wang et al. [1] fabricated continuous carbon fiber reinforced polyphenylene sulfide (PPS) composites and monitored interlaminar thermal damage was monitored using real-time measurement of electrical of interlaminar interface. Recently Thostenson and Chou [2] developed multi-wall CNTs reinforced glass fiber-epoxy laminated composites and they used the distributed sensory network of CNTs to evaluate the onset and the evolution of damage in their composites. In this study, thermoset epoxy was reinforced with two different particulates and using the percolation network generated using multi-walled CNTs in epoxy, extensive experimentation is conducted to understand the deformation, onset of damage and growth in these composites. 1.1 Fabrication Procedure A two-part thermoset epoxy (Part-A: resin and Part-B: hardener) is used as a matrix. The specific gravity of part-A is 1.1299 and part-B is 0.97 and the mix ratio is 5:1.95. Multiwalled CNTs having a diameter of 30±15 nm and length of 520 micron are used to generate percolation network in the system. Two types of particulates namely cenospheres and glass bubbles were used as reinforcement in the epoxy matrix. The cenospheres are a by-product of the fly ash, obtained from coal-fired power plants and glass bubbles are the microscopic spheres of glass which simulate the conditions of porosity. First, MWCTs of 0.5 wt% are added to epoxy resin and later mix is shear mixed for 30 minutes and ultrasonicated for 60 minutes. In the second step, the particulate materials are introduced and mixed using a shear mixer. The solution is degassed separately to remove the entrapped air. Both the parts are then mixed thoroughly and degassed again to remove any air entrapped during mixing. The mix is poured in suitable molds to make the desired test specimens. Proper care is taken not to induce any air bubbles while pouring the mix into the moulds. The reason Proceedings of the SEM Annual Conference June 7-10, 2010 Indianapolis, Indiana USA ©2010 Society for Experimental Mechanics Inc. 83 T. Proulx (ed.), MEMS and Nanotechnology, Volume 2, Conference Proceedings of the Society for Experimental Mechanics Series 2, DOI 10.1007/978-1-4419-8825-6_13, © The Society for Experimental Mechanics, Inc. 2011
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