Kamal Sharma

Three-phase carbon fiber amine functionalized carbon nanotubes epoxy composite: processing, characterisation, and multiscale modeling

The present paper discusses the key issues of carbon nanotube (CNT) dispersion and effect of functionalisation on the mechanical properties of multiscale carbon epoxy composites. In this study, CNTs were added in epoxy matrix and further reinforced with carbon fibres. Predetermined amounts of optimally amine functionalised CNTs were dispersed in epoxymatrix, and unidirectional carbon fiber laminateswere produced. The effect of the presence of CNTs (1.0 wt%) in the resin was reflected by pronounced increase in Youngs modulus, inter-laminar shear strength, and flexural modulus by 51.46%, 39.62%, and 38.04%, respectively. However, 1.5wt% CNT loading in epoxy resin decreased the overall properties of the three-phase composites. A combination of Halpin-Tsai equations and micromechanics modeling approach was also used to evaluate the mechanical properties of multiscale composites and the differences between the predicted and experimental values are reported. These multiscale composites are likely to be used for potential missile and aerospace structural applications.

Molecular modeling of the mechanical behavior of carbon fiber-amine functionalized multiwall carbon nanotube/epoxy composites

This paper presents a molecular dynamics (MD) analysis to parametrically describe the mechanical behavior of carbon fiber-amine functionalized multiwall carbon nanotube (A-MWCNT)/epoxy composites. The functionalized CNTs are first embedded in epoxy and cured to increase the micromechanical interlocking between CNTs and matrix. Carbon fibers were later used as fillers to increase the overall mechanical properties of the three-component composites. Within the model, the carbon fiber volume fraction was fixed at 60% and the CNT volume fraction was changed from 0.25% to 5%. Results show that the Young’s modulus and tensile strength along the carbon fiber direction increased from 92 to 224.4xa0GPa and from 1.35 to 2.85xa0GPa, respectively, with increasing the CNT volume fraction from 0.25% to 5%. [New Carbon Materials 2014, 29(2): 132–142]

Experimental study of mechanical properties of multiscale carbon fiber-epoxy-CNT composites

Recently intensive research has been carried out on carbon nanotube (CNT) based polymer composites. However, in this work the macro scale IM700 carbon fiber (CF) has been integrated with amino modified multi-wall carbon nanotubes (MWCNT-NH2) within LY-556 epoxy matrix to produce three-phase, multi-scale composites, with the applications in missiles. The fictionalization of CNTs has been carried out for improved and consistent mechanical and physical properties. High frequency probe sonication method was used for homogenous dispersion of CNTs. Mechanical characterization of the multiscale composites fabricated by hand layup process included tensile, flexure and inter-laminar shear stress tests. The addition of small amounts of MWCNTs (upto 1.5 weight %) for the fabrication of multiscale composites resulted in a maximum enhancement in tensile strength by 23% , flexural modulus by 35%, flexural strength by 5% and ILSS by 7%. CF/epoxy composites (without CNTs) have also been characterized for comparison with MWCNT-NH2 /CF/ epoxy composites. For a more accurate prediction of the Young’s moduli of multi-scale composites several micromechanical models (Voigt-Reuss, Halpin-Tsai, and modified mixture Law) compared with the experimental work. These models have been tested for upto 1.5 weight % of CNTs. The difference of approximate 28% of the values in Young’s modulus has been reported in the classical micromechanical models and experimental results and it comes out 11% for CF/epoxy composites as they do not have reinforcement of CNT’s within it. In all the classical models, the Young’s moduli of the carbon nanotube composites were used as matrix properties.

Molecular dynamics evaluation of mechanical properties of carbon nanotubes with number of Stone-Wales defects

Molecular dynamics simulation has been carried out to study the mechanical properties of a 42.59 Å long armchair (6, 6), (8, 8), (10, 10), and (12, 12) single-walled carbon nanotubes (SWCNTs) with an increase number of Stone-Wales (SW) defects, by varying their relative position and orientation. Brenner bond order potential has been employed for energy minimization. In the present work, calculations of fundamental mechanical properties of SWCNTs were performed using molecular dynamics (MD) simulations via material studio by Accelrys Inc. Maximum percentage reduction of 7.5 % in Youngs modulus and increase in potential energy which is also accountable to stabilize carbon nanotubes (CNT), observed as 26.8%. Strain amplitude 0 .003 is employed and no of steps for each strain is 4. During the simulation 0.001 kcal/mol energy, 0.5 kcal/mol/Å force, maximum number of iteration 500 with Steepest Descent Algorithm has been used. The fluctuation of the total energy and temperature during the MD were also calculated. This simulation carries an optimized structure before calculating the Youngs modulus.