Date on Master's Thesis/Doctoral Dissertation
8-2024
Document Type
Doctoral Dissertation
Degree Name
Ph. D.
Department
Mechanical Engineering
Degree Program
Mechanical Engineering, PhD
Committee Chair
Kate, Kunal
Committee Co-Chair (if applicable)
Satyavolu, Jagannadh
Committee Member
Bhatia, Bikram
Committee Member
Wang, Hui
Author's Keywords
natural fibers; composites; thermoplastic; 3D printing; additive manufacturing; sustainability
Abstract
Carbon fiber is widely known for its exceptional strength, making it a sought-after material in composite manufacturing, especially with thermosets and thermoplastics. Its major applications span aerospace, wind turbines, sports equipment, automotive interior and exterior parts, robotics and medical equipment. Recently, carbon fiber filament manufacturing has gained attention due to the availability of desktop 3D printers and the versatility and customizability that comes with the realm of 3D printing. Commercial carbon fiber production, primarily from polyacrylonitrile (PAN), is energy-intensive and derived from crude oil, contributing to significant environmental impacts and poor recyclability. Alternatively, lignocellulosic natural fibers present a possible sustainable option due to their abundance, carbon neutrality, and cost-effectiveness. These fibers, derived from plants such as rice, corn and soy, are agricultural residues from the highest crop production in the Unites States and they offer more sustainable processing techniques compared to carbon fibers and potential in composite fabrication through additive manufacturing.
This dissertation investigates the use of rice husks, soy hulls, and corn fiber, in 3D printing composites. One of the biggest challenges in natural fiber reinforced composites is the fiber-polymer interfacial properties, which can be improved by different pretreatment methods. Chemical and thermal pretreatment methods are explored in this study to improve their compatibility with thermoplastic polymer matrix. Rice husk is first investigated for its reaction to different acid and alkali pretreatment that could defibrillate and delignify the fibers. This fiber is first explored as it contains a higher amount of silica which posed its own set of challenges overcome two stages of hydrolysis treatment. The insights gained from chemically pretreating rice husks are then applied to thermally pretreating the fibers to improve the stiffness that is lost through delignification. Low temperatures are subjected onto the rice husks to surface char the biomass without altering the bulk to preserve stiffness and achieve carbon fiber properties. Carbonization at low temperatures not only consumes less energy but also prepares the surface of the fibers to promote better fiber-polymer bonding. The results from studying rice husks in 3D printing composite filaments provides better understanding of natural fibers and how they behave when subjected to different pretreatment methods. Hence, this study is extended to soy hulls and corn fiber, which contain lower amount of lignin. The effects of acid hydrolysis, low temperature carbonization and a combination of both are examined to better understand the changes that occur to natural fibers and how they can improve the properties of thermoplastic composites. The findings suggest that natural fibers, through appropriate pretreatment and processing, can potentially supplement synthetic carbon fibers, offering a more sustainable alternative for composite manufacturing.
Recommended Citation
Surendran, Athira Nair, "Natural fiber reinforced composites for sustainable additive manufacturing." (2024). Electronic Theses and Dissertations. Paper 4446.
Retrieved from https://ir.library.louisville.edu/etd/4446
