Masters Theses

Date of Award

5-2023

Degree Type

Thesis

Degree Name

Master of Science

Major

Mechanical Engineering

Major Professor

Dr. Uday Kumar Vaidya

Committee Members

Dr. Merlin Theodore, Dr. Ryan Ginder

Abstract

The use of carbon fiber (CF) composites is growing in non-aerospace markets, such as the automotive and transportation sectors. More than 30% of the CF produced ends up as waste material in landfills at end of life (EOL) from sources such as decommissioned aircraft and industrial components. CF retains its properties over decades and offers significant benefits if recycled and repurposed. Recycled CFs (rCF) are less expensive than virgin fibers, and composites made from rCF have mechanical properties that are acceptable for a variety of non-aerospace applications. In this study, a homogenous mixture of rCF-polypropylene (PP) was achieved using the Resonant Acoustic Mixing (RAM) technique, where water was used as a mixing solvent. The nonwoven composite's mechanical properties and molding conditions are influenced by how well the fibers are aligned. Randomly oriented nonwovens have similar mechanical properties in all directions and can be manufactured using a wet-laid (WL) process, whereas highly aligned nonwoven textiles can be manufactured using carding process. Therefore, nonwoven rCF-PP mats were fabricated using carding and WL techniques to understand the effect of fiber orientation on mechanical properties. In this study we observed that carding machine parameters such as pin length, cylinder width, distance between cylinders have influence on final mechanical properties. The mats were compression molded to obtain consolidated panels. Mechanical, microscopic, and fiber length distribution characterization was performed to determine the properties variation between the two manufacturing techniques. The flexural strength and modulus of carding in the machine (along the fibers) direction (MD) was 22% (from 86.89 ± 5.1 MPa to 105.99 ± 12.42 MPa) and 72% (from 5.14 ± 0.5 GPa to 8.85 ± 1.3 GPa), respectively higher as compared to wet-laid. Further, the tensile strength and modulus of carded composites in MD were 75% (from 35.51 ± 5.1 MPa to 62.10 ± 4.8 MPa) and 110.8% (from 6.58 ± 1.81 GPa to 13.87 ± 1.57 GPa), respectively higher than WL process. This work has broad applications in product development with rCF in many commercial and commodity sectors such as sporting goods, automotive, medical devices, etc.

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