Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Materials Science and Engineering

First Advisor's Name

Benjamin Boesl

First Advisor's Committee Title

Co-Committee Chair

Second Advisor's Name

Arvind Agarwal

Second Advisor's Committee Title

Co-Committee Chair

Third Advisor's Name

Daniela Radu

Third Advisor's Committee Title

Committee Member

Fourth Advisor's Name

Seung Jae Lee

Fourth Advisor's Committee Title

Committee Member

Keywords

Cyanate Ester, Boron Nitride Nanotube, BNNT, Polymer, High Temperature Polymer, Composite, In Situ, In Situ Mechanical Testing, Aerospace Composites, Hierarchically Structured Composites

Date of Defense

3-28-2023

Abstract

The objective of this study was to develop a novel strategy for fabricating thermally stable, hierarchical boron nitride-based reinforced cyanate ester composites by leveraging the known degradation mechanisms of cyanate esters and utilizing the exceptional properties of 1D and 2D boron nitride nanoparticles.

Specifically, we covalently bonded hydroxyl functionalized boron nitride nanotubes (BNNTs) with cyanate ester monomers, forming imino-carbonate linkages. By exploiting this bonding pathway, a new class of composites that exhibit superior mechanical and thermal properties were created. The addition of just one volume percent of functionalized BNNTs to cyanate ester reduced the curing activation energy to a value lower than any previously reported literature value, increased the hardness and elastic modulus by 18.48% and 12.42%, respectively, and improved the thermal conductivity by 5.69%. These results were attributed to the covalent bond allowing for superior interfacial interactions between the two materials, improving the dispersion within the matrix and leading to more efficient thermal and mechanical energy transfer.

A significant outcome of this research was the fabrication of novel hierarchically structured foam composites consisting of boron nitride nanoplatelets (BNNPs) and BNNTs. Through reinforcing cyanate ester with these highly aligned and high-volume percent architectures, the thermal conductivity was increased by an incredible 104.5%. The enhanced thermal conductivity of the foam structure was primarily attributed to the tailored orientation of its constituent materials, the BNNPs and BNNTs. The alignment of the BNNPs along the walls of the foam and the networked formed by BNNTs interconnecting individual nanoplatelets and micro-pores created a synergistic effect which facilitated a highly conductive pathway for heat transfer, making it a promising candidate for a wide range of thermal management applications.

This research provides a pathway for reinforcement of other polymer systems and can lead to the development of incredibly strong and thermally stable polymers for high temperature applications. The multifunctionality of the boron nitride system in these composites can be exploited for advanced applications such as sensors and radiation shielding structures. Overall, these findings provide valuable insights into the design and manufacturing of high-performance materials and have significant implications for a range of industrial and scientific applications.

Identifier

FIDC011079

ORCID

https://orcid.org/0000-0002-9154-4219

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