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Browsing by Author "Yourdkhani, Mostafa, advisor"

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    Advanced manufacturing of thermoset polymers and composites
    (Colorado State University. Libraries, 2023) Ziaee, Morteza, author; Yourdkhani, Mostafa, advisor; Radford, Donald W., committee member; James, Susan, committee member; Bailey, Travis, committee member
    Thermoset polymers and composites are lightweight materials extensively used in many industries from aerospace to automotive to prosthetics due to their excellent specific mechanical properties and high chemical resistance. However, these products are conventionally manufactured by labor-intensive processes using subtractive manufactured tooling or molds followed by thermal curing inside an oven or autoclave at elevated temperatures for several hours. Hence, conventional manufacturing approaches are energy- and time-consuming and require expensive equipment. Moreover, lack of design flexibility and poor repeatability are additional challenges, which limit the structural and functional capabilities of such products. In this dissertation, I present a novel approach to address the existing limitations in manufacturing thermosets and their composites by developing rapid curing resin systems and integrating them in additive manufacturing (AM) processes. In the first chapter, state-of-the-art manufacturing methods are reviewed and frontal polymerization (FP) as a promising curing strategy for rapid and energy-efficient manufacturing of thermosets and composites is introduced. In the second chapter, the effect of ambient conditioning and resin chemistry on thermal frontal polymerization of a high-performance resin system is explored. In the third chapter, FP is used to demonstrate, for the first time, simultaneous printing and curing of short carbon fiber-reinforced composites for high performance applications. In the following chapter, AM of a soft and stretchable elastomer with tunable thermomechanical properties manufactured via FP is discussed. In the fifth chapter, the printing process is further improved using an external localized heat source, instead of relying on the exothermic heat of polymerization of the resin, to accelerate the curing rate and make the printing process more robust and applicable to the manufacture of large-scale components. Finally in the last chapter, bubble-free frontal polymerization of polyacrylates is introduced for the developed 3D printing process.
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    Towards automated manufacturing of composites via thermally assisted frontal polymerization
    (Colorado State University. Libraries, 2024) Jordan, Walter Patrick, author; Yourdkhani, Mostafa, advisor; Zhao, Jianguo, committee member; Simske, Steve, committee member
    Current methods for the manufacturing and repair of fiber-reinforced thermoset composites are energy-intensive, slow, and costly due to extensive processing steps and expensive equipment required to achieve complete cure. This is especially true for large, complex geometries that require autoclaves and prolonged cure times. As a result, there is a need to develop faster, cost-effective, energy-efficient processes. With the implementation of rapid curing thermoset resins, the cure cycle can be reduced from hours to minutes. This research focuses on the development, implementation, and testing of these resin systems in the established fields of mobile additive manufacturing and filament winding to demonstrate unprecedented, rapid manufacturing of composite parts. Additive manufacturing of fiber-reinforced thermoset composites is desirable due to its inherent ability to produce custom, complex parts quickly, with minimal required tooling. By printing and simultaneously curing the composite as it is deposited, freeform unsupported structures with high mechanical properties can be created. One limitation of current additive manufacturing methods is the print volume associated with traditional gantry style additive manufacturing systems. By combining the highly desirable properties of additive manufacturing using rapid, thermally curable resin systems with the mobility of a mobile additive manufacturing system, large, mechanically sound structures with virtually no limitations on print volume can be created. Moreover, rapid curing thermoset resin systems have the potential to revolutionize traditional composite manufacturing processes. Due to its wide range of applications and its ubiquitous nature, filament winding serves as a natural starting point to do so. Traditional filament winding is typically a two-step manufacturing process, where the composite part is first wound on a rotating mandrel and then cured using autoclaves or ovens. By combining these processes on the winding machine, the labor involved in manufacturing, the energy required for curing, and the overall production time are significantly reduced. In this research, a mobile additive manufacturing robot is designed, validated, and optimized for accurate locomotion and fast, dimensionally accurate printing of composite structures with high fiber alignment and degree of cure. The capabilities of this system are exhibited throughout several demonstrations that involve printing unsupported structures upside-down, the manufacturing of a bridge strong enough for the robot to pass over, and bridging the material across a 60 cm gap. Additionally, a pre-existing filament winding machine is optimized for the manufacturing of large, geometrically unconstrained composite structures. Improvements in fiber volume fraction are achieved through processing changes and a thermal profile for dry fibers is established to facilitate identification of frontal polymerization.