ORCID

Luke Salisbury: https://orcid.org/0009-0001-1529-6081

Degree

Bachelor of Science (B.S.)

Major(s)

Mechanical Engineering

Document Type

Immediate Open Access

Abstract

The advent of additive manufacturing has revolutionized the prototyping, design, and manufacturing of new and innovative products. Through the use of Fused Deposition Modeling (FDM), parts can be manufactured using different sparse infill percentages (the percentage of void space within a printed object) and sparse infill patterns (the lattice structure of material within the object). Through the manipulation of these variables, the same material and part can have different compressive and flexural properties. In addition to sparse infill, the thermoplastics used in fused deposition modeling can be reinforced with carbon fiber strands to create a printable composite material capable of strengthening and stiffening parts without increasing the amount of material used. This experiment evaluated the yield stress performance of 3DXTech’s CarbonX PETG+CF filament printed at varying infill densities and infill patterns in hopes of characterizing the minimum structural properties of commonly used lattice structures. The infill patterns were evaluated at 15%, 35%, 50%, and 75% along with a baseline 100% infill with no internal pattern. The two-dimensional infill patterns (infill patterns that do not vary along the z-axis) rectilinear and triangles along with the three-dimensional infill patterns (infill patterns that vary along the z-axis) cubic, gyroid, and 3D honeycomb were tested on the surface perpendicular to the print orientation in order to test the minimum compressive strength of each specimen. All test specimens used were derived from the same STL document and manufactured by Bambo Lab’s X1 Carbon at a resolution of 0.2mm with a nozzle temperature of 260 oC, and the printer was programmed using the g-code created by Bambu Lab’s Bambu Studio slicing software. For each infill density and infill pattern, four test specimens were tested to failure using the Shimadzu Autograph AGX-V2 and its associated software. The yield strength, absolute strength, and stress vs. strain graph of each specimen were derived from the data collected along with photography and projectional radiography of the failure mode. The findings of this research can be summarized as three-dimensional infill patterns being characterized as having larger yield stresses than two dimensional infill patterns along their weakest face, increasing infill density universally increases the yield stress of the object, and objects of higher infill densities buckle at the middle of the specimen, acting as uniform bodies, while lower infill densities tend to buckle at the top and bottom of the specimen. More research is needed to further characterize the effects of stress on PETG-CF lattice structures, but this research can be used to guide the selection of print parameters depending on expected compressive loads.

DOI

https://doi.org/10.54718/KTEF6581

Date Defended

12-6-2024

Thesis Director

Dr. Wayne Huberty

Second Committee Member

Dr. Han-Gyu Kim

Third Committee Member

Dr. Matthew Peaple

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