All ETDs from UAB

Advisory Committee Chair

Selvum Pillay

Advisory Committee Members

Siddhartha Brahma

Haibin Ning

Vinoy Thomas

Ruigang Wang

Document Type


Date of Award


Degree Name by School

Doctor of Philosophy (PhD) School of Engineering


The quest for sustainable materials and manufacturing techniques has spurred research into distinct composite materials that utilizes recycled thermoplastics in combination with natural hemp fibers and recycled carbon fibers. This dissertation delves into the processing of recycled high-density polyethylene (rHDPE) with hemp fiber and separately, with recycled carbon fiber (rCF), scrutinizing their suitability as environmentally friendly and economically viable materials. The study focuses on distinct processing methods used for hemp fiber and recycled carbon fiber: compression molding with hemp mats as well as extrusion compression molding, additive manufacturing, and injection molding for recycled carbon fiber, while the recycled carbon fiber segment compares various manufacturing methods and assesses material crystallinity through cooling rates using Differential Scanning Calorimetry (DSC).The effects of sodium hydroxide (NaOH) treatment to modify the hemp fibers and optimize their performance, including their chemical composition, tensile strength, and overall suitability as a reinforcing material in rHDPE composites are analyzed. The experimental results indicate that the NaOH treatment significantly influences the mechanical properties of the hemp fiber-reinforced composites. The recycled carbon fiber aspect of the dissertation compares the performance and characteristics of rHDPE composites with recycled carbon fiber using three distinct processing methods: extrusion-compression molding, additive manufacturing (3D printing), and injection molding. The study focuses on mechanical properties, microstructural analysis, and material crystallinity. Comparisons between the different manufacturing methods reveal critical insights into the suitability of each for specific applications and the resultant material properties. Furthermore, the crystallization of the rHDPE composites was examined through the cooling rates using DSC, shedding light on the effects of processing conditions on the final material structure. The data collected provides a comprehensive understanding of how the addition of rCF impacts the crystalline structure of the composites and, consequently, their mechanical and thermal properties. This dissertation contributes to the field of sustainable materials by offering a thorough investigation of the processing of recycled high-density polyethylene in combination with hemp fiber and recycled carbon fiber. The outcomes of this study will aid in the development of eco-friendly materials and manufacturing processes for a variety of applications, ranging from automotive to construction, and support the ongoing efforts to reduce the environmental impact of material production.

Included in

Engineering Commons



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