SCHOOL OF MECHANICAL ENGINEERING SEMINAR Monday, May 28, 2012 at 15:00 Wolfson Building of Mechanical Engineering, Room 206

M.Sc. student of Prof. Leslie Banks-Sills, School of Mechanical Engineering, Tel-Aviv University

Since their discovery in 1991, Carbon Nanotubes (CNTs) have been of great interest. No previous material has displayed the combination of superlative mechanical, thermal and electronic properties attributed to them. These properties make nanotubes ideal for a wide range of applications. In particular, owing to their unique mechanical properties, CNTs are considered to be ideal candidates for polymer reinforcement.

Yet, successful reinforcement is still a great challenge. Improvement of the interface between the matrix and the CNTs, as well as homogeneous dispersal of the CNTs while maintaining a high aspect ratio are necessary in order to realize the full potential of CNTs as a filler to reinforce polymers. In this investigation, two approaches, experimental and modeling, were adopted in order to evaluate the effective mechanical properties of Polymethyl-methacrylate (PMMA) reinforced with CNTs.

Experiments included a series of uniaxial tensile tests guided by ASTM D 638-08 (2009). Dog-bone specimens of neat PMMA and PMMA containing CNTs of weight fractions 0.5%, 1%, 2% and 6% were tested. The tests were displacement controlled, while images were taken of the gage area. Specimen preparation included spraying paint onto their surface in order to create a random speckle pattern for evaluation of the inplane displacement field by means of Digital Image Correlation (DIC). The image processing procedure, Vic-2D, was performed for each test. A MATLAB program was then used to calculate strains, to create stress-strain curves and determine E, Young's modulus, ν, Poisson's ratio, σf , stress to failure and εf , strain to failure.

In addition, simulations were carried out using the High-Fidelity Generalized Method of Cells (HFGMC). A Repeating Unit Cell (RUC) consisting of one CNT and PMMA surrounding it was modeled and analyzed in order to determine the effective mechanical properties of the composite. A two-dimensional model was used to describe infinite CNTs, while a three-dimensional model was carried out for CNTs with a lower aspect ratio. Damage parameters were used to model debonding between phases. The effects of CNTs' concentration, size and orientation were also examined.

Evaluation of the Effective Mechanical Properties of PMMA Reinforced with CNTs - Experiments and Modeling

Or Ben David