Semester

Fall

Date of Graduation

2025

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Konstantinos Sierros

Committee Member

Edward Sabolsky

Committee Member

Thorsten Wuest

Abstract

Additive manufacturing, commonly known as 3D printing, has the potential to transform the production of end-use parts by facilitating the creation of complex shaped, low-volume components that are expensive to manufacture using traditional methods. However, thermoplastic polymer matrices currently utilized in 3D printing of carbon fiber composites, often lack the mechanical properties needed for aerospace applications. To address this issue, researchers have developed fiber-reinforced 3D-printed composites using an innovative two-step process which involves printing 3D preforms using fused deposition modeling, followed by compression molding. However, most previous work involves the use of nylon-based polymer matrices while there are a number of other potential candidate materials which have been little researched and maybe advantageous in terms of performance. In this work, alternative thermoplastic polymer matrices including Poly Ether Ketone Ketone (PEKK-A+CF15), Polyetherimide (PEI 9085+CF15 and PEI 9085), Thermoplastic Polyamide (TPI), and Polyphenylene Sulfide based (PPS and PPSU) matrices are explored. A comprehensive experimental investigation was conducted on the above polymers, with and without short carbon fiber reinforcement, using thermal analysis while 3D printability was accessed and optimized. In addition, an investigation of surface and bulk defects using microscopy techniques was performed along with mechanical characterization to evaluate the tensile, flexural, impact, and dimensional properties of each matrix. The findings indicate that PEKK-A+CF15, PEI 9085+CF15, PEI 9085, and PPSU are viable alternative matrix materials for 3D printing whereas TPI and PPS present additional challenges, as both polymers exhibited warping during and after the printing process, with PPS samples also exhibiting significant porosity and gaps. In terms of mechanical properties, PEKK-A+CF15 exhibits the best performance in both tensile and 3-point bending while PEI 9085 exhibits the highest impact strength. Finally, printed parts with carbon fiber exhibit the most dimensional accuracy. In summary, this research demonstrates that alternative polymer matrix materials, which are not largely considered for 3D printing of aerospace composites currently, have the potential to be implemented in such applications thus offering opportunities for performance enhancements.

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