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Variably Dense Objects
Experimental analysis to determine the effects of infill pattern and density on part strength using uniaxial tension tests.
Project Overview
- Course: Mechanics of Solids and Structures (ENGR2320)
- Project Prompt: “Design and conduct an analytical experiment that enhances your understanding of the content covered in the course”
- Timeframe: 2 weeks
- Year: Spring 2024
Process
I’ve
always wondered whether the infill pattern I choose when preparing a 3D
print has any affect on the strength of my final part. So, for my final
Mechanics of Solids and Structures (MechSolids) project, I wanted to
conduct an experiment that would tell me just that.
Along with
two teammates, I conducted a series of 24 uni-axial tension tests with
3D printed ‘dog bone’ samples. We tested for two different variables:
infill density and infill pattern. The density tests were performed at
15%, 30%, 45%, and 60%, using the grid infill pattern. The
pattern tests were performed with the cubic, gyroid, and 3D honeycomb
patterns. For each variable, we tested 3 identical samples and averaged
the collected data between them to get 7 sets of data.
Diagram showcasing the infill densities and patterns tested
Photo of a fractured 3D printed dog bone sample in the jaws
of the Instron machine used for tension testing
After
conducting tests on all 24 samples and condensing the results into 7
sets of load and extension data, we analyzed the results based on the
ultimate tensile strength, fracture stress, extension at fracture, and
modulus of toughness.
Through this analysis, we produced a number of plots:
Plot comparing the resulting stress-strain curves from all 7 data sets
Plot comparing the ultimate tensile strength between each data set
Plot comparing the stress at fracture between each data set
Plot comparing extension at fracture between each data set
Plot comparing modulus of toughness between each data set
Based
on these comparisons, we determined that increasing infill density is a
way to increase part strength under uni-axial load. However, there
appears to be no difference in overall part strength between different
infill patterns. When infill density is increased, more material is
being added to the inside of the object, and therefore distributes force
over a greater area over a given cross-section. Infill pattern,
however, only arranges the same amount of material in different ways and
not increasing the area over which a force is distributed.
After our analysis was complete, I used Adobe Illustrator to create a final poster to showcase our work to our peers: Final Poster created in Adobe Illustrator
Reflection
This
project offered a valuable opportunity to bridge theoretical knowledge
of material mechanics with practical application. Designing and
conducting uniaxial tension tests allowed me to gain a deeper,
intuitive understanding of how forces act on complex objects. Observing
the physical effects of tension and analyzing the corresponding data
provided meaningful insights into the process of determining material
properties, reinforcing the connection between experimental results and
theoretical principles.