Document Type

Thesis - Open Access

Award Date

2019

Degree Name

Master of Science (MS)

Department / School

Mechanical Engineering

First Advisor

Todd Letcher

Keywords

Composite, Cuttlefish, Flexure property, Modified, Nylon, Stiffness

Abstract

Flexure strength is one of the most widely used mechanical properties to represent the mechanical behavior of the composite. Fiber reinforcements increase the flexure strength of a composite. Specifically, there has been tremendous growth in the use of Carbon Fiber (CF) in the manufacturing industry due to its significant contribution to enhance the mechanical properties of a composite. Fiber orientation, void content, bonding between the layers (delamination), and fiber distribution are some of the factors that affect the flexure strength of a reinforced composite. The laminate (composite with reinforced layers) composites, has been a focus of study by researchers from years. Laminate composites possess good strength, which enhances the overall strength of the composite. The current study focuses on 3d printed laminate composites. The Markforged Mark Two is capable of printing continuous CF reinforced composites using nylon reinforced by continuous CF. Material samples were created using the Markforged Mark Two and were flexure tested using the MTS Insight testing machine. The experimental results were analyzed using a MATLAB script. The results have shown that there is a significant effect on the flexure properties of the composite, with variation in CF orientation and CF distribution. The maximum Flexure Modulus was found to be 11.074 GPa in 0⁰ fiber-oriented specimen with 3-3-layer proximity fiber distribution. The maximum Yield Strength and Ultimate

Flexure Strength were found to be 210.7 MPa and 210.7 MPa respectively, in the same specimen. Experimental data was used to calculate the Stiffness of flexure specimens. Flexure specimen with 0⁰-fiber orientation having 3-3 fiber-layer proximity has shown maximum Stiffness of 119.64 N/mm among all other test specimens with 15º or alternating + 45º and - 45º or 90º fiber orientation with different fiber distributions such as 2-2-2-layer proximity or 1-1-1-1-1-1-layer proximity or 6-fiber layer proximity.

Sea creatures, crab shells, and spider webs are some of the species that inspire us to examine their structures. Nature evolves to find methods of using fewer resources to complete a task more efficiently. Therefore, it is important to study and understand nature inspired structures.

One such nature inspired structure is the Cuttlefish bone. Cuttlefish bone is a special class of ultra-lightweight, hard, brittle internal structure found in all members of the Sepiidae family, commonly known as Cuttlefish. Cuttlefish live in ocean waters at hundreds of meters of depth, with high water pressure. Thus, the Cuttlefish bone has evolved into a cellular material that possesses unique mechanical and structural properties that allow the Cuttlefish to survive in these conditions.

Scientists have studied various Cuttlefish bone internal structures to understand its compressive strength, by making necessary assumptions and morphological changes in its internal structure. In this research, a small portion of its internal structure called Representative Volume Element (RVE) was modified and compression tested for its stiffness studies. The Cuttlefish bone internal structure is a difficult structure to manufacture using traditional manufacturing techniques. However, additive manufacturing (i.e., 3D Printing) can produce similar structures. A Markforged Mark Two printer was employed to print the structure, which used nylon as a matrix material for continuous CF reinforcements. The same structure was also printed using Poly Lactic Acid (PLA) for stiffness studies. The RVE and modified RVE of Cuttlefish bone structure printed using different materials were compression tested using the MTS Insight testing machine and the results were compared. The results have shown that there is a significant difference between the stiffness of RVE and the modified RVE of Cuttlefish bone structure.

Library of Congress Subject Headings

Flexure.
Carbon fiber-reinforced plastics.
Cuttlefish.
Three-dimensional printing.
Composite materials.

Format

application/pdf

Number of Pages

82

Publisher

South Dakota State University

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Manufacturing Commons

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Rights Statement

In Copyright