Damage-Induced Response

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Structural materials often fail because small cracks grow quickly, especially during events like earthquakes, leading to dangerous conditions and expensive repairs. I wanted to explore whether materials could respond to damage as it happens, rather than after failure has already occurred.

I was inspired by the idea of self-healing materials and how engineering can improve safety in real-world systems. Instead of focusing on repairing damage, I chose to study how fluids can be delivered directly into cracks when they form. To test this, I created composite samples with different numbers of small fluid-filled tubes embedded inside. I then broke the samples in a controlled way and observed how the fluid spread through the cracks.

I found that increasing the number of tubes increased both the amount of fluid released and how evenly it spread. This shows that fluid delivery systems can be designed to respond effectively to damage and improve coverage in cracked regions.

This work could help improve the design of safer, more resilient materials used in buildings and infrastructure. By improving how materials respond to cracks, it may be possible to reduce damage, lower repair costs, and increase safety in environments where structural failure is a risk.

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I began by researching self-healing materials and how engineers study crack formation and failure in structures. I focused on reliable sources such as scientific articles and engineering publications to understand how fluids can be delivered within materials when damage occurs.

To investigate this, I designed a composite system using a solid epoxy material with small sealed tubes containing dyed liquid embedded inside. These tubes acted as internal fluid reservoirs. I created multiple samples that were identical in size and composition but differed in the number of embedded tubes to test how tube density affects fluid delivery.

Each sample was intentionally weakened at a specific point to ensure cracks would form in a consistent location. The samples were then subjected to controlled force until fracture occurred. When the material cracked, the tubes intersecting the crack broke and released fluid. The spread of this fluid was captured on paper and used to analyze how effectively it was distributed.

The independent variable was the number of embedded tubes, while the dependent variable was the area and pattern of fluid spread. Controlled variables included sample size, material composition, tube size, and testing method.

Data was collected by comparing the spread patterns and estimating the area covered by the fluid. Multiple samples were tested across different tube densities to identify trends.

This approach allowed me to isolate how design changes influence fluid delivery in cracked materials without focusing on the healing process itself.

Cover photo credit of: "notegpt.io" https://notegpt.io/ai-image-generator

Photo #2 credit of: Amazon.ca. (n.d.). Glass capillary tubes [Product image]. https://www.amazon.ca/dp/B0FC2DPB91

The results show that increasing the number of embedded capillary tubes improves how effectively fluid is delivered when a crack forms. As tube density increased, the fluid covered a larger area and spread more evenly along the crack path. The negative control sample showed no fluid release, while the low-density sample produced a small, localized spread. The medium-density sample showed a larger, more radial pattern, and the high-density sample produced the largest and most uniform coverage.

Qualitatively, the spread patterns appeared to increase in a roughly linear way based on visual size. However, when the spread area was measured and compared, this relationship was not linear. The approximate measured areas were about 0 cm² for 0 tubes, 25–30 cm² for 4 tubes, 30–35 cm² for 8 tubes, and around 75–80 cm² for 12 tubes. This shows a much larger increase at higher densities than expected from visual observation alone.

All tubes consistently ruptured during fracture. This indicates that tube breakage was not a limiting factor in fluid delivery. Instead, the main factor influencing the results was how many tubes intersected the crack and released fluid into the damaged region. As the number of tubes increased, the likelihood of interaction with the crack also increased, leading to greater fluid release and improved distribution.

The non-linear increase in spread area suggests interaction effects between tubes. At higher densities, more fluid is available, and fluid from multiple tubes can combine and travel further along the crack. This results in larger and more continuous coverage patterns. The shift from localized to radial spread patterns supports this observation.

The spread patterns also provide insight into how fluid moves through cracks. Localized patterns indicate limited flow, while radial patterns suggest that fluid is able to move along the crack and spread outward more effectively. This indicates that both fluid availability and crack geometry influence the final distribution.

However, the results also suggest that increasing the number of tubes may eventually become less efficient. At higher densities, it becomes much more difficult to propagate a crack, due to the glass tubes acting similarly to rebar within concrete. More force was required to create a break with the composite.

Overall, the results demonstrate a clear relationship between capillary tube density and fluid delivery effectiveness, while also showing that this relationship becomes increasingly non-linear at higher densities.

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The results show that increasing the number of embedded capillary tubes improves how effectively fluid is delivered when a crack forms. As tube density increased, the fluid covered a larger area and spread more evenly. This supports the conclusion that fluid delivery in this system is mainly controlled by how much fluid is available and how the crack interacts with the embedded tubes, rather than whether the tubes break. All tubes consistently ruptured during fracture, indicating that tube breakage is not a limiting factor. Instead, the key factor is how many tubes intersect the crack and contribute fluid to the damaged region. This means that system design—such as tube placement and density—is critical for improving performance. The results also suggest that there may be a point where increasing the number of tubes becomes less efficient, as fluid coverage begins to overlap. This indicates that an optimal balance is needed between maximizing coverage and using fluid efficiently. From this project, I learned that designing effective materials involves more than just adding components; it requires understanding how different factors interact under real conditions. These findings are important because they show how materials can be engineered to respond to damage in real time. This could lead to safer, more durable structures in applications such as buildings, bridges, and other infrastructure where cracks can lead to failure.

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This project could be improved by increasing the number of trials for each tube density to strengthen reliability and allow for statistical analysis. While fluid spread area was measured quantitatively, future work could include measuring fluid flow rate and volume released to better understand delivery efficiency. Testing different tube arrangements and orientations would help determine an optimal design. In addition, using different types of fluids with different viscosities could show how flow behavior affects distribution. The next step would be to develop interconnected channel systems to improve control and efficiency in real-world applications.

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I would like to sincerely thank my parents for their constant support and motivation throughout this project. Their encouragement pushed me to stay focused and keep improving my work.

Thank you to my chemistry teacher Mrs. Van Gaal for her guidance, helpful discussions, and for challenging my ideas in a way that strengthened this project.

I also want to thank my girlfriend, Callie, for her patience and for listening to me talk through my ideas and progress at every stage.

Your support made this project possible.

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References

Amazon.ca. (n.d.). Glass capillary tubes [Product image]. https://www.amazon.ca/dp/B0FC2DPB91

Anderson, T. L. (2017). Fracture mechanics: Fundamentals and applications (4th ed.). CRC Press.

Callister, W. D., & Rethwisch, D. G. (2020). Materials science and engineering: An introduction (10th ed.). Wiley.

Hager, M. D., Greil, P., Leyens, C., van der Zwaag, S., & Schubert, U. S. (2010). Self-healing materials. Advanced Materials, 22(47), 5424–5430. https://doi.org/10.1002/adma.201003036

NoteGPT. (2025). AI image generator [AI-generated image tool]. https://notegpt.io/ai-image-generator

OpenAI. (2026). ChatGPT (GPT-5.3) [Large language model]. https://chat.openai.com Used only for grammatical editing and organizing notes written by the developer (e.g., logbook).

Toohey, K. S., Hansen, C. J., Lewis, J. A., White, S. R., & Sottos, N. R. (2007). Self-healing materials with microvascular networks. Nature Materials, 6(8), 581–585. https://doi.org/10.1038/nmat1934

White, S. R., Sottos, N. R., Geubelle, P. H., Moore, J. S., Kessler, M. R., Sriram, S. R., Brown, E. N., & Viswanathan, S. (2001). Autonomic healing of polymer composites. Nature, 409(6822), 794–797. https://doi.org/10.1038/35057232