Date of Award

2025-12-01

Degree Name

Doctor of Philosophy

Department

Mechanical Engineering

Advisor(s)

Yirong Lin

Abstract

Additive manufacturing (AM) is rapidly reshaping the landscape of advanced materials for aerospace, hypersonic, and extreme-environment systems. However, AM of high-temperature polymer and ceramic composites, especially those reinforced with continuous or aligned fibers, remains limited by challenges in rheological control, in situ fiber impregnation, curing compatibility, densification, and achieving directional multifunctional properties. This dissertation advances a unified Direct Ink Writing (DIW) framework enabling the processing of architected, high-performance composite materials across polymer and ceramic systems. Three research thrusts collectively establish scalable pathways for fabricating fiber-reinforced cyanate ester interpenetrating polymer networks (IPNs) and ultra-high-temperature ceramic matrix composites (UHTCMCs). First, a dual-curable cyanate-ester/tri-acrylate (CE-T-acrylate) IPN system was formulated with tunable shear-thinning behavior suitable for DIW. UV–thermal sequential curing produced a robust IPN network, achieving glass transition temperatures (Tg) up to 349 °C, excellent thermal stability, and high mechanical retention at elevated temperatures. DIW-printed IPN specimens retained nearly 80% of their room-temperature strength at 200 °C, demonstrating their suitability for high-temperature structural applications.

Second, this work introduces a novel DIW process for in-situ impregnation and deposition of continuous carbon fiber (CCF) within the CE–IPN matrix using a custom-modified nozzle. The approach enabled stable fiber alignment, strong interfacial bonding, and complex 3D toolpaths unattainable by traditional thermoset processing. The resulting composites exhibited more than threefold increases in flexural strength (280.12 ± 25.19 MPa) and modulus (19.77 ± 0.96 GPa) at a fiber volume fraction of 11.9 ± 0.3%, and also exhibited significant multifunctional enhancement, with longitudinal electrical conductivity exceeding 407 S/m. Finally, the dissertation extends DIW to the ceramic domain by formulating SiC-fiber-reinforced ZrB2–SiC suspensions using SMP-10 preceramic polymer. Scalable DIW printing followed by controlled pyrolysis produced UHTCMCs with tailored fiber alignment, reduced thermal anisotropy, and improved functional performance. Directional pyrolysis nearly doubled thermal conductivity, while fracture strength increased substantially with fiber addition despite intrinsic porosity. These results demonstrate DIW as an enabling route for topology-controlled, fiber-reinforced UHTCs for hypersonic thermal-protection and extreme-environment structures. Collectively, this dissertation establishes DIW as a powerful manufacturing platform for high-temperature polymer and ceramic composites with engineered architectures, multifunctionality, and enhanced structural performance. The methodologies, processing insights, and structure–property relationships developed herein provide a foundation for next-generation aerospace materials and future advancements in scalable composite additive manufacturing.

Language

en

Provenance

Received from ProQuest

File Size

99 p.

File Format

application/pdf

Rights Holder

Saqlain Zaman

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