Abstracts

Nanomaterials have attracted much attention due to theexcellent properties they possess and their promising applications.The combination of 3D printing and composite materials hasredefined the mechanical properties of 3D printed products. In thisresearch, nylon (PA) 6 nanocomposites filled with either carbonnanotubes(CNTs), graphene or graphene-NH2 were 3D printed togetherwith Kevlar fibers into specimens for mechanical tests and othercharacterizations. Different weight percentages of CNTs andgraphene were used to produce the nanocomposites, in order tofigure the properties of each nanoparticle reinforced PA 6. Themelt mixed CNTs or graphene nanocomposites were extruded intofilaments and used in the 3D printer. A Markforged printer allowedthe production of continuous Kevlar fiber reinforcednanocomposites. The tensile and flexural tests revealed that thebest weight percentage of CNTs is 0.5wt%, where the entanglementsand agglomerates of CNTs were not so obvious. Surprisingly, theCNTs filled PA 6 nanocomposites did not show as significantimprovements in mechanical properties as graphene filled PA 6, dueto the weak interfacial interactions between the CNTs and the PA 6matrix. The addition of Kevlar fibers increased the tensilestrength and flexural modulus of PA 6 by 526% and 1388%. Also, thetensile fatigue results showed that 1%CNT/PA 6+Kevlar specimenshave the longest fatigue life among the materials tested.Graphenefilled PA 6 presented much better improvements in mechanicalproperties. With only 0.1wt% of graphene, the tensile modulusimproved by 101% and with 1wt% of graphene the modulus improved by153%. Additionally, although Kevlar fibers dominate the mainmechanicalproperties of these composite materials, the existence ofgraphene also contributes to the enhancement of strengths andmoduli, unlike CNTs.Strong interfacial bonding allows efficientload transfer between matrix and reinforcement. Therefore,graphene-NH2/PA 6 showed significant improvements in both tensileand bending strengths. The tensile modulus of 0.1% graphene-NH2/PA6 and 1% graphene-NH2/PA 6 are increased by 212% and 253%.Flexuraltests showed obvious difference between different nanoparticlefillers. However, the anisotropic specimens did not show muchdifference between different weight percentages of the same kind ofnanocomposite.It is found that the well-dispersion of nanoparticlesin the matrix and strong interfacial bonding between the filler andthe matrix are the main reasons for the enhancement of mechanicalproperties of nanocomposites. The addition of Kevlar fibersimproved the stiffness and strength of the compositessignificantly.Advisors/Committee Members: Shi, Jing (Committee Chair).