Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Engineering Science

Program

Mechanical and Materials Engineering

Supervisor

Wood, Jeffrey T.

Abstract

Discontinuous short fiber carbon reinforced polymer (CFRP) composites were manufactured, and tested to demonstrate feasibility, and to document material properties. Different variations of manufacturing techniques were tested including continuous fiber reinforcement, metal inserts, and randomization of the dry fibers before processing. The process produced parts with strength to weight ratios similar to 6061-T6 aluminum without continuous fiber reinforcement, and 53% higher when small volumes of continuous reinforcement are added. Randomization of fibers produced no significant change in strength of the material, but did increase compression stiffness of the mixture while molding, increasing tool deflection. A pin joint was tested, and different methods of calculating the maximum stress were compared.

Summary for Lay Audience

A carbon fiber reinforced epoxy composite was manufactured and then tested to determine the material properties. The manufacturing technique consisted of mixing a two-part epoxy with 0.25-inch-long randomly oriented carbon fibers and then placing the mixture inside an aluminum mold. Air was pulled out from the mold using a vacuum system, and then a plunger compressed the mixture to minimize cavities. Once the epoxy cured, the part was removed from the mold. The parts were destructively tested to measure their stiffness and strength in bending and tension.

Different variations of the manufacturing technique were tested to observe the result on manufacturing cycle times and the strength and stiffness. These variations included complete randomization of the fibers, and additional reinforcement of the part with long, continuous fibers of carbon. Additionally, pin pullout tested was done to simulate a pin connection with the goal of recommending a method to predict when it would break.

The process produced parts with strength to weight ratios similar to a common aluminum alloy. Once reinforced with continuous fibers, the composite had a 53% higher strength to weight. Randomization of fibers produced no significant change in strength of the material. For the pin joint, different methods to predict when the failure would occur were compared.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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