Liquid crystal thermoplastic filament for three-dimensional printing

Description (excerpt)

JOINT RESEARCH RELATED TO THE INVENTION This invention is a “Subject Invention” which resulted from research and development activities undertaken pursuant to Cooperative Research and Development Agreement (CRADA) Joint Work Statement No. 19-043-001 entitled “Additive Manufacturing of Multi-component Self-Reinforced High-Performance Thermoplastics” between U.S. Army Combat Capabilities Development Command (DEVCOM) Army Research Laboratory (ARL) and 3F, LLC. RELATED APPLICATION DATA This non-provisional patent application claims benefit to U.S. Provisional Patent Application No. 63/645,560 of the same title filed on May 10, 2024. Additionally, this non-provisional patent application is a continuation-in-part (CIP) application of and claims priority to and the benefit of U.S. Non-Provisional application Ser. No. 16/814,353 titled “Multi-material polymer filament for three-dimensional printing” filed on Mar. 10, 2020 which claims the benefit of U.S. Provisional Application No. 62/817,161 titled “Multi-Material Thermoplastic Filament with Regular Geometry for Extrusion Additive Manufacturing” filed on Mar. 12, 2019. The '353 application in turn is a continuation-in-part (CIP) application of and claims priority to and the benefit of U.S. Non-Provisional application Ser. No. 15/630,175, titled “A process for creating a filament,” filed on Jun. 22, 2017, which the present application also claims priority to. All of the above-identified provisional and non-provisional patent applications and all documents attached or filed with the above-identified provisional and non-provisional patent applications are hereby incorporated by reference herein. GOVERNMENT INTEREST The invention described herein may be manufactured, used and licensed by or for the U.S. Government. FIELD The present invention relates generally to the field of materials. More specifically, materials and devices are provided for use in production of complex fibers for three-dimensional printing. In particular aspects, materials and material structures are provided that provide superior capabilities in formation of complex fibers. BACKGROUND Fused filament fabrication (FFF) is the most commonly implemented additive manufacturing technique, in terms of volume of material, number of parts made, number of printers sold annually, and number of trained operators. FFF involves feeding a thermoplastic polymer filament into a heated print head, melting the filament, and then extruding the molten filament onto a build plate. The print head and build plate have computer-controlled motion so that the extrudate can placed trace by trace, and layer by layer, to build a 3D part. A typical filament diameter is 1.75 or 2.85 mm, and a typical extrudate diameter is 0.5 mm. FFF is widely implemented due to a number of key advantages, including low-cost materials and printers, feedstock with very long shelf life, simple operation with low hazards, and accurate geometry. The key disadvantage to FFF is the poor mechanical properties of FFF parts. Between layers, interfaces are very weak due to insufficient time for melt, wetting, and molecular reptation across the interface. Along the trace direction, strength and stiffness values are comparable to injection molded thermoplastics. Chopped or milled fibers, typically carbon/graphite or glass, can be added to the thermoplastic to improve mechanical properties. These chopped fiber loadings rarely exceed 20% vol. which, combined with the small aspect ratios of chopped fibers, results in only modest gains in stiffness and strength compared to unreinforced polymer. Introducing chopped fibers also adds considerable cost, accelerates mechanical wear of printer components such as nozzles, and may also reduce mechanical toughness. Some commercial and research print technologies have been developed to combine thermoplastic filaments with continuous fibers, typically carbon fiber or glass fiber. These printers are highly specialized for a number of reasons. Continuous fibers cannot stretch, so one cannot continuous feed, melt, and extrude through a conventional converging nozzle; e.g., a 1.75 mm continuous fiber reinforced filament cannot be forced through a 0.5 mm nozzle. To overcome this challenge, specialized print heads are required, such as ones that merge fiber and thermoplastic at the print head, or depositing a pre-impregnated reinforced filament or tow without a reduction in diameter. Another challenge is that stopping material deposition requires a mechanical, thermal, or electrical means of cutting the continuous fiber as it is deposited. For these reasons, there does not exist a continuous fiber feedstock that can be implemented widely in conventional FFF printers, while the continuous fiber printers that do exist are very expensive, challenging to operate, and requ