Thermomechanical characterization of nanoreinforced composites

The objective of this investigation is to characterize the thermomechanical behavior of nanoreinforced epoxy. The resin employed in this investigation is a bisphenol F epoxide with a diamine curing agent. The nanofillers are single walled carbon nanotubes and vapor grown carbon nanofibers. The objective of the tests carried out with nanotube reinforced epoxies is to assess the effects of chemical functionalization on the behavior, whereas the objective of the tests with nanofibers is to assess the effects of mass fraction of reinforcement on behavior. Some of the nanotubes were functionalized with amine groups to improve chemical bonding with epoxy. Nanofiber mass fractions varied from 0.5 to 10%. Processing methods employed an air-release agent, surfactant, and high frequency sonic agitation, which resulted in good dispersion of the nanofibers and nanotubes. The types of thermomechanical properties evaluated were glass transition temperature (T_g), coefficient of thermal expansion (CTE), and tensile creep behavior. The composite containing amine-functionalized nanotubes showed an increase of 10°C in T_g, and a 3/°C decrease in CTE. Use of functionalized nanotubes did not increase the creep resistance of epoxy as expected. It was found that, as nanofiber content increased from 0 to 10%, the T_g of the composites decreased by 12°C, the CTE remained roughly constant, and the creep compliance decreased by about 50%.