Synthesis and mechanical characterization of polyamide-imide/zinc oxide nanocomposites towards applications in aerospace

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Dallas Kesler (Creator)
The University of North Carolina at Greensboro (UNCG )
Web Site:
Hemali Rathnayake

Abstract: Low Earth orbit poses unique challenges to spacecraft due to its harsh environment. Of particular concern is the presence of small, fast moving natural and manmade micrometeoroids whose collisions with spacecraft cause damage that greatly reduces their effective lifetime. Polyimide materials, such as PMR-15, have been used since the dawn of the space age given their favorable physiochemical properties and strength to mass ratio as compared to structural materials like ceramics and metals. Recent research on polymer nanocomposites has demonstrated the inclusion of nanoparticles into polymer matrices can enhance the mechanical properties of structural materials. Further, considerable attention has been given to investigate mechanical properties of metal oxide nanomaterials reinforced polymeric systems, particularly focusing on zinc oxide nanoparticles and their inclusion into various polymeric systems. In this regard, this thesis focuses on understanding viscoelastic behavior of zinc oxide nanorods reinforced polyamide nanocomposites. A series of polyamide-imide based nanocomposites were fabricated by blending polyamide-imide resin with different weight ratios of zinc oxide nanorods, and their viscoelastic properties were characterized via nanoindentation. A positive correlation among elastic modulus, stiffness, and hardness were found, with the strongest response coming from the composite with 4.76 wt % zinc oxide which increased reduced elastic modulus, stiffness and hardness by 32%, 14%, and 35%, respectively. Additionally, creep compliance calculations demonstrated a decrease in composite creep under constant stress as zinc oxide nanorod weight composition increased, with the same trend holding for delayed viscoelastic response; creep compliance values decreased from 3570 Pa-1 to 1717 Pa-1 with the addition of 4.76 wt % zinc oxide nanorods and delayed viscoelastic response decreased from a 2.2% change in depth over 0.51 seconds for the zinc oxide free material to a 1.1% change in depth over 0.30 seconds for the nanocomposite containing 4.76 wt % zinc oxide. The roughness analysis along with topological analysis of nanocomposites films with respect to the weight ratio of ZnO nanorods support the changes in viscoelastic responses, evidencing highest favorable interactions between nanorods and polymer chain in the composite with 4.76 wt % ZnO nanorods, maximizing polymer flow restriction and minimizing deformation. Finally, calculations estimating the velocity of elastic waves and the Hugoniot Elastic Limit demonstrated addition of zinc oxide nanorods improve elastic wave speed, with the nanocomposite containing 4.76 wt % zinc oxide nanorods having an elastic wave speed of 3.57 km/s, which is an 11% improvement as compared to free polymer itself. The improvement in elastic properties, elastic wave speed, and Hugoniot Elastic Limit imply the 4.76 wt % zinc oxide nanorods containing nanocomposite would better resist hypervelocity impacts than nanorod free material. The future work will focus on performing hypervelocity impact testing using the facility at the Marshall Space Flight Center. [This abstract has been edited to remove characters that will not display in this system. Please see the PDF for the full abstract.]

Additional Information

Language: English
Date: 2020
Metal oxide nanoparticles, Nanocomposite, Nanoindentation, Polyamide-imide, Polyimide
Zinc oxide
Nanocomposites (Materials)

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