Project Overview
In this investigation, different internal structures of 3D printed objects were evaluated to optimize their shock absorption capabilities. These prototypes were each three inches thick and tested at collision speed of 6.82 mph. To test them, a pendulum-like device was created where an arm would swing and hit the prototype at a constant speed and force. Each design was also tested five times, with their averages being calculated. A Mass-Force Index (Prototype Mass x Max Force) and a Mass-Deceleration Index (Prototype Mass x Max Deceleration x -1) were created to compare designs. A lower output was favorable since it would indicate the design would be lightweight and cheap all while exhibiting good shock absorption properties. Furthermore, the prototype would have to prevent the testing arm from penetrating the prototype completely and yield an impact force and deceleration below 250 N and -245m/s (-25G) respectively.
A series of prototypes were tested including a standard hexagon, zigzag, thin-hexagon and a combination of a zigzag and hexagon design. During the conclusion it was determined the standard hexagon was the most favorable with Indexes. However, this investigation proved that it is difficult to create a standard shock absorber optimized for every situation. Every situation is different with unique needs, the design that was proven optimal was only optimal based on the testing specifications put in place. Furthermore, a series of errors could have impacted on the results including print discrepancies and temperature & humidity impacting both the prototypes properties and the measuring devices.
Research Methodology
To determine the optimal internal structure, thorough research was conducted on current infill patterns used in 3D printing, including honeycomb, grid, and other common geometries. The findings helped inform the design of custom infill patterns and aided in the creation of future iterations.
In order to test and evaluate each prototype, a pendulum-like testing device was constructed. Each prototype would be placed in a fixed location and the arm of the device would hit each prototype at a consistent speed. Sensors were attached to the arm to measure the force and deceleration upon impact. Each prototype was tested five times to ensure accuracy, and the average values were calculated for comparison. Furthermore all impacts were recorded using a high-speed camera to analyze the deformation and energy absorption characteristics of each design.
Like stated earlier, two indexes were created to compare each design: the Mass-Force Index and the Mass-Deceleration Index. These indexes took into account both the mass of the prototype and the measured force and deceleration, providing a comprehensive metric for evaluating shock absorption performance relative to weight. Using these two indexes as well as fixed requirements for maximum force and deceleration, each design was compared and ranked accordingly.
Key Findings
After testing 4 different infill patterns, it was determined that the standard hexagon design provided the best shock absorption properties based on the Mass-Force and Mass-Deceleration Indexes. This design effectively distributed the impact forces, resulting in lower peak forces and decelerations compared to other patterns tested. While a combined zigzag and hexagon design showed promise, it did not outperform the standard hexagon in this specific testing scenario, due to the higher costs assoicated due to increased material usage and print time.
Future Directions
Future work could explore additional infill patterns, variable impact speed, angle and materials. Furthermore attempting to create more unique infill patterns that are optimized for shock absorption could be beneficial.
Overall this experiment provided valuable insights and learning opportunities into the field of 3D printing and shock absorption, as well as testing methodologies, design of experiments and data analysis techniques.