The addition of nanoparticles into polymer materials has been observed to dramatically change the mechanical, thermal, electrical, and diffusion properties of the host polymers, promising a novel class of polymer matrix composite materials with superior properties and added functionalities that are ideal candidates in many applications, including aerospace, automobile, medical devices, and sporting goods. Understanding the behavior and underlying mechanisms of these polymer nanocomposites is critical. The research work presented in this dissertation represents one of the initial efforts in the long journey pursuing the ultimate understanding of nanoparticle reinforced polymer systems. Particular focal points are experimental evaluation and the development of appropriate modeling methods to capture the influence of the interphase on the overall viscoelastic behavior of carbon nanotube reinforced polymer nanocomposites. The first portion of this dissertation study investigates the viscoelastic behavior of MWCNT based PMMA nanocomposites, which complements our previous study of SWCNT/PMMA systems to confirm functionalization of nanotubes as an effective way to manipulate the interaction between nanotube and polymers and control the properties of the interphase region forming around the nanotubes and consequently change the overall performance of nanotube based polymer nanocomposites. In the second portion of this dissertation, we present a novel hybrid numerical-analytical modeling method that is capable of predicting viscoelastic behavior of multiphase polymer nanocomposites, in which the nanoscopic fillers can assume complex configurations. By combining the finite element technique and a micromechanical approach (particularly, the Mori-Tanaka method) with local phase properties, this method operates at low computational cost and effectively accounts for the influence of the interphase as well as in situ nanoparticle morphology. This modeling method is implemented two-dimensionally on nanotube and nanoplatelet based polymer nanocomposites. Given the experimentally measured frequency domain response of the bulk polymer, the viscoelastic behavior of the nanocomposites in both frequency and temperature domains can be calculated. The predicted pattern of influence of the interphase on the overall performance of the nanocomposites is consistent with the experimental observation. 3D parametric studies utilizing this modeling technique reveal that the nanotube morphology "modifies" the effect of interphase and hence profoundly influences the overall viscoelastic behavior. The findings help explain some experimental observations and furthermore, draw attention to the importance of morphology control through appropriate synthesis and processing techniques to further tune the thermomechanical behavior of the nanocomposites.

Last modified

• 08/29/2018

Creator

• Hua Liu

DOI

• https://doi.org/10.21985/N2GH82

Subject

• Mechanical Engineering

Keyword

• polymer nanocomposite
• viscoelastic behavior
• carbon nanotube
• interphase
• morpholohy

Date created

• 2007-12-05

Resource type

• Dissertation

Rights statement

• In Copyright