Toughening mechanisms in multiphase nanocomposites
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Toughening mechanisms in multiphase nanocomposites S. A. Meguid • J. M. Wernik • F. Al Jahwari
Received: 15 February 2013 / Accepted: 4 March 2013 / Published online: 23 March 2013 Ó Springer Science+Business Media Dordrecht 2013
Abstract Our research is concerned with nanoreinforced structural adhesive bonds (SAB) for aerospace applications that contain dissimilar substrates and a theromoset epoxy adhesive with dispersed nanofillers. The interactions between these different phases results in unique fracture properties and mechanisms that dictate the toughness of the nanocomposite. In view of the varied length-scale, one cannot implement mere traditional approaches to evaluate the possible toughening mechanisms needed to ensure the integrity of the multiphase nanocomposite. Our current research is devoted to establishing the appropriate toughening mechanisms in multiphase nanocomposites by adopting traditional mechanisms such as crack-bridging, crack deflection, crack pinning and void nucleation, as well as investigating new nano-mechanisms such as fracture ridge creation. In this paper, the toughening mechanisms of carbon nanotube (CNT) reinforced polymer SABs are identified and their effects quantified in order to effectively estimate the fracture toughness of nanocomposite. Specific attention is devoted to examining the effect of dispersion of the nanofillers upon the strengthening mechanisms and interfacial debonding in nanocomposites, and the propensity of agglomerationsassisted crack initiation sites using atomistic based continuum modeling techniques. S. A. Meguid (&) J. M. Wernik F. Al Jahwari Mechanics and Aerospace Design Laboratory, University of Toronto, Toronto, ON M5S 3G8, Canada e-mail: [email protected]
Keywords Nanocomposites Carbon nanotubes Toughening Atomistic based continuum
1 Introduction Multiphase nanocomposites are composites containing several materials of varying class and size. Their importance comes from the collaborative effect of the different phases in enhancing desired properties of a certain structure. Fracture toughness is one of the most important properties of any material for many design applications. It is already well established that the incorporation of a second phase micron size particles whether soft or hard, can significantly enhance the fracture toughness of certain materials through different toughening mechanisms as those described for epoxies by Garg and Mai (1988). Since the emergence of nanotechnology, nano-fillers such as nanoparticles and nanotubes are used as reinforcements. Nano-fillers opened a wide range of potential to new superior engineered materials due to the outstanding properties of such fillers and the larger contact area compared to the micron-size fillers. With that larger contact area, a good adhesion between nanofillers and their surrounding matrix is most likely to be the key for the overall improvement of multifunctional nanocomposites. As the fracture toughness is concerned in this paper, a good adhesion to the matrix interfere
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