If we compare carbon fibre and polypropylene for AFO materials, then Carbon Fibre will offer superior support, durability, and comfort, because of the high- strength-to-weight ratio and adaptability with up to 95% Carbon content,  it is expected to outperform Polypropylene in meeting the needs of individuals with ankle and foot issues. 

 

 

Carbon Fibre/Polypropylene AFOs                 

Background Research

                                                                                                                   Aydin & Strahinja

 

The two materials we will be contrasting are Carbon Fibre and Polypropylene. Carbon Fibre (or Carbon Fibre reinforced plastic) is carbon atoms formed together in a crystalline arrangement. Polypropylene is a thermoplastic that stands as very stress-resistant. 

 

Carbon Fibre was first created in 1860 by Sir Joseph Wilson Swan to make a variant of the early incandescent light bulb. In 1879, Thomas Edison took credit for making carbon fibre, a polymer which is chemically bonded with large molecules. With the process of cooked cotton threads or as an alternative, bamboo silvers at high temperatures. The chemical reaction of this assembles carbon fibre filament. Later on, it evolved to higher performance and was used in many more aerodynamic products. Polypropylene was commercially produced in the year 1957 by a chemical company known as Hurcules Inc. Initially made as a resin as propathene in 1954. A Nobel Prize was awarded for the chemistry of polypropylene in 1963.       

 

Polypropylene was discovered in 1951 by Italian chemist Giulio Natta and German chemist Karl Ziegler, who were awarded the Nobel Prize in Chemistry in 1963 for their work in polymer production. Initially synthesized during attempts to develop new forms of gasoline, polypropylene's potential quickly became apparent. Its versatility and favourable properties led to its widespread adoption across various industries, including packaging, textiles, automotive, and healthcare. Since its discovery, polypropylene has undergone continuous refinement and optimization, resulting in the development of specialized grades tailored to specific applications. Today, polypropylene remains one of the most widely used thermoplastics globally, contributing significantly to modern manufacturing and innovation.

 

Carbon fibre has been around for about 150 years but really hasn’t changed in the first 75 years. People realized the great strength-to-weight ratio of Carbon Fibre, which consists primarily of carbon atoms bonded together in a repeating pattern, often represented by the chemical formula C. This discovery led to innovations such as replacing tungsten with Carbon Fibre for lightbulb filaments. Engineers explored various applications for Carbon Fibre, leveraging its lightweight properties and structural integrity. However, it's worth noting that Carbon Fibre is typically only about 20% carbon, limiting its potential for maximum strength utilization compared to pure carbon materials. Also using “Bacon’s” method to create it is greatly inefficient. As well as very expensive to make. Without sacrifices, modern-day carbon fibre has all the benefits, it is 55% carbon, meaning stronger, and cheaper. Credited to a technology company in Japan made in the early 1960s. Modern-day carbon fibre was updated in the 1970s, 95% carbon with the same benefits as the others but better. In 1991, the UK shut down all non-organic carbon fibre manufacturers due to concerns over environmental pollution and the use of toxic chemicals in the production process.. Polypropylene does not have nearly as much evolution, it was created by accident in 1951 when a scientist attempted to make propylene into gasoline, but it underwent the process and turned into a high-density polyethylene and hasn’t been modified since. But in the end, it’s a recent discovery.

 

Polypropylene is a thermoplastic polymer. It is widely used in various applications due to its versatility, affordability, and favourable mechanical properties. Polypropylene AFOs offer a balance of flexibility and durability, making them suitable for individuals with different mobility needs. The polymer's molecular structure allows for easy customization to conform closely to the wearer's foot and ankle, enhancing comfort during prolonged use.

 

Carbon fibre has its pros and cons when it comes to being environmentally friendly. The first point is that it can’t biodegrade, the reason being that it’s meant to be a strong stable structure. Also, it is complicated to repurpose carbon fibre depending on the manufacturing process ( some are built more “green”). However it is not all bad, when considering the natural resources in carbon fibre, it is 50%-71% all-around carbon. Lignin-based carbon fibre is sustainable in it being a natural resource located in cell walls ( plants). Polypropylene is relatively safe for the environment. It is fully recyclable, has a low carbon footprint, doesn’t release toxins, and is 100% safe for humans; however, it's not fully sustainable.

 

Carbon Fibre AFOs offer excellent strength and durability, providing robust support for individuals with ankle and foot issues. They are lightweight, minimizing fatigue during prolonged use, and can enhance stability during physical activities like running and jumping. However, Carbon Fibre AFOs tend to be more expensive than other materials, making them less accessible to some individuals. Additionally, their rigidity may limit flexibility and comfort for some wearers, requiring careful consideration of individual needs and preferences when selecting AFO materials.

 

Polypropylene AFOs are more flexible and adaptable, conforming closely to the wearer's foot and ankle for enhanced comfort. They are generally more affordable than Carbon Fibre AFOs, making them accessible to a wider range of individuals. However, Polypropylene AFOs may lack the same level of strength and durability as Carbon Fibre counterparts, potentially requiring more frequent replacements. Additionally, their flexibility may not provide sufficient support for rigorous physical activities, necessitating careful consideration of activity level and functional needs when choosing AFO materials.

 

AFOs (Ankle Foot Orthosis) are support devices for ankles and feet and rely on different materials like carbon fibre and polypropylene. These materials beat out the old ones made of metal or hard plastic. Some newer techniques, such as 3D printing, help tailor AFOs for better fits and performance for various people.

The cost of AFO has a wide range of price, some as low as $80 and some as high as $1000. It hinges on what they're made of, how customised they are, and the manufacturing process. Carbon fibre, though a bit pricier due to its strength and lightness, requires specific skills for use. On the other hand, polypropylene, being more affordable, is great for crafting custom AFOs. But sometimes, shelling out more for the higher-priced material is necessary for better support or durability.

Carbon fibre, with its incredible strength and lightness, offers solid support without the weight. Its adaptable nature makes it an excellent choice for those needing robust support. Polypropylene, on the other hand, is flexible, budget-friendly, and easily moulded to fit the body. While not as robust as carbon fibre, it still provides good support and is perfect for those requiring a bit of flexibility.

Choosing the right material for AFOs is a big deal. It affects how comfortable and supportive they are. AFOs made from carbon fibre are tough and last long, while polypropylene ones are flexible and fit nicely. Picking the right material helps people with movement issues move better and feel more stable. New ways of making these devices mean they can be just right for each person, making life easier and more comfortable for them. Carbon fibre-reinforced plastic and polypropylene are two different types of materials that have different properties and uses. Carbon fibre-reinforced plastic is a composite material made up of carbon fibres encapsulated in a polymer matrix, usually epoxy. It is known for its high strength-to-weight ratio and high stiffness, making it ideal for use in aerospace and automotive applications as well as in sports equipment and other high-performance applications. Density is good scientific evidence of performance. The lightweight material is slightly denser than water standing at 1.75g/cm3.

 

Carbon fibre AFOs are typically made by layering thin strands of carbon fibre fabric in specific orientations and impregnating them with epoxy resin. The composite material is then cured under heat and pressure to create a rigid and lightweight structure. Polypropylene AFOs, on the other hand, are usually fabricated by heating and melting polypropylene pellets, which are then injected or molded into the desired shape. Once cooled, the polypropylene material solidifies, forming a flexible yet supportive orthotic device.

 

On the other hand, Polypropylene is a thermoplastic polymer that is known for its flexibility and impact resistance. It is commonly used in a wide range of applications, including packaging, consumer goods, and automotive parts. In summary, the main difference between these two materials is that Carbon Fibre is known for its high strength and stiffness as well as it being aesthetic and lightweight, while Polypropylene is known for its flexibility and impact resistance. The density of Polypropylene can be comparable to water as it is 0.895-0.925 g/cm3, making it comparably less dense than H2O(1g/cm3). 

 

These materials have properties they don't share but both need to make an exceptional AFO. Suppose there was a method of melting these two and contrasting them into a balance of stiffness and being able to be stable when used and to have flexibility/mobility with the product to improve potential performance. This will create an overall new material.

Choosing the right material for making AFOs is really important. Some people might need strong support, and for them, Carbon Fibre is great because it's tough and not heavy. On the other hand, Polypropylene is good because it's more flexible, letting people move a bit more comfortably. But the cost can be a factor too – Carbon Fibre can be pricier than Polypropylene.

So, picking between Carbon Fibre and Polypropylene depends on what someone needs. Carbon Fibre is strong and lasts long, while Polypropylene is flexible and fits nicely. Deciding which material to use helps orthotics create AFOs that provide the right kind of support for people who need help with their ankles and feet.

 

Variables:

Running test:

• Manipulated - AFO used
• Responding -  Amount of time it took to complete the course
• Constant - Track used to run, amount of meters ran, Outfit worn, amount of energy, and experience of running

Jumping test:

• Manipulated - AFO used
• Responding - Height that was reached with a jump
• Constant - size of sticky notes, energy level, force and speed build-up for the jump, and experience of jumping

Procedure:

Running Test:      

1. Preparation: 

• Ensure AFOs are properly fitted and secured.
• Wear appropriate running shoes for each AFO.

2. Set-up:

• Pick a measured track or a method reliable to measure distance.
• Make a setup of a timer/stopwatch.

3. Testing Process:

• Run a consistent distance (e.g., 100 metres) using both AFOs.
• Track the time it took to complete each trial for the two AFOs.

4. Data Collecting:

• Record the running times and write down any comfortability and stability observations for each AFO.

5. Data Synthesis:

• Calculate the average of the results gathered from the running. times for each AFO.
• Calculate the performance difference for each AFO.

Jumping Test:

1. Preparation:

• Go to a setting of a wall with a reasonable height to reach with a jump.

2. Set-up:

• Stand facing a wall with a sticky note on either one of your hands.

3. Testing Process:

• Execute ten jumps with each AFO.
• Mark the heights reached with the sticky notes stuck.

4. Data Collection:

• Measure the height from sticky note to ground for each AFO.

5. Data Synthesis:

• Calculate the average height reached by sticky notes for each AFO.
• Compare and analyze the vertical jumping performance of each AFO.

 

Observations:  

• During Aydin’s runs, we made sure to give him breaks with water to balance results to be fair. With this rule, we noticed that Aydin needed longer breaks with the polypropylene brace. This is likely due to comfort from running. Comfortability is required to decrease the chance of feeling sore, cramped, or injured.

• As for stability, we noticed that Aydin's technique of running was slightly more postured with carbon fibre compared to polypropylene, it was looking slightly worse but we wouldn’t say it's drastic to affect the results. But could be associated with his need for longer breaks in between runs.
• Although results present that Aydin’s carbon fibre jumps were accomplished more adequate results, it seemed as he looked bouncier and moderately flexible compared to the carbon fibre. Even though it didn’t show as good, it looked higher quality in the method.
• During Aydin’s jump trials, he managed to maintain an unpredictable result instead of the results getting better or worse when doing his trial. 
• Towards the end of each running trial, Aydin got motive to finish faster and get a faster run trial for the last 20 metres to really give it his all
• Aydin’s carbon fibre jump trials were more stiff and kept giving the wall solid impact with his body which led to a harder time to stick the tape against the wall, where as polypropylene didn’t have that issue and had Aydin manage to clear trials with ease.

Analysis: 

 

Our science fair project comparing Carbon Fibre and Polypropylene for ankle-foot orthosis (AFOs) is very interesting. Carbon Fibre has been around since the 19th century and has come a long way, finding uses in light bulbs and aerodynamics. It's gotten stronger over time, especially with advancements in Japan in the 1960s. On the other hand, Polypropylene was stumbled upon in 1951 while trying to make gasoline, and it hasn't changed much since. When it comes to the environment, Carbon Fibre doesn't break down easily, and repurposing can be tough. But it has a decent amount of carbon from natural sources. Polypropylene is seen as more eco-friendly since it's recyclable, has a low carbon footprint, and is safe for humans. AFOs, the devices for ankles and feet, have transitioned from old, rigid materials to the flexibility of Carbon Fibre and Polypropylene, showing progress in orthotics. The materials used in ankle foot orthoses (AFOs) play a critical role in shaping not just the physical structure of the device, but also the wearer's mobility, comfort, and overall quality of life. Carbon Fibre and Polypropylene, the focus of our comparison, represent two ends of the spectrum in terms of material properties and their impact on AFO functionality. Carbon Fibre, renowned for its strength-to-weight ratio and rigidity, offers unparalleled support and stability. When incorporated into AFOs, Carbon Fibre can effectively redistribute forces exerted on the foot and ankle, enhancing stability during weight-bearing activities like walking or standing. This increased stability can be transformative for individuals with conditions such as drop foot or ankle instability, allowing them to navigate daily tasks with greater confidence and reduced risk of falls. Moreover, the lightweight of Carbon Fibre minimizes the burden on the wearer, promoting ease of movement and reducing fatigue during prolonged use. This aspect is particularly advantageous for individuals who lead active lifestyles or engage in sports, as it enables them to pursue physical activities with greater comfort and efficiency. On the other hand, Polypropylene offers a different set of advantages, primarily its flexibility and adaptability. Unlike the rigidity of Carbon Fibre, Polypropylene has a degree of flexibility that allows it to conform more closely to the wearer's foot and ankle. This personalized fit not only enhances comfort but also gives a more natural pattern, promoting fluidity of movement and reducing the risk of discomfort or skin irritation associated with prolonged wear. For people whose mobility needs vary throughout the day or who require greater flexibility during activities such as bending or squatting, Polypropylene AFOs offer a versatile solution that can accommodate a range of movements without compromising support or stability. The cost of AFOs varies based on the material, customization, and manufacturing. Carbon Fibre is a bit pricier but is known for strength and lightness, while Polypropylene is more affordable, making it good for customized AFOs. The cost of Carbon Fibre AFOs can range from $500 to $1500 or more, depending on factors such as customization, design complexity, and additional features. In contrast, Polypropylene AFOs generally range from $200 to $600, making them a more budget-friendly option for many individuals. I believe the idea to use Carbon Fibre and Polypropylene for an AFO material with a balance of stiffness and flexibility is forward-thinking. It could bring something new to orthotic design. The comparison of Carbon Fibre's strength and longevity to Polypropylene's flexibility and comfort is a great juxtaposition. The density comparison, where Carbon Fibre is slightly denser than water and Polypropylene is less dense, adds a technical touch to the experiment. So, why should people care? Well, the materials used in AFOs directly impact the comfort, support, and mobility of individuals with ankle and foot issues. This experiment sheds light on the choices available and their implications. If successful, the idea of combining Carbon Fibre and Polypropylene could revolutionize orthotic design, potentially leading to more effective and adaptable orthotics. This isn't just about scientific curiosity; it's about improving the quality of life for the people who depend on AFOs. Understanding the environmental aspects of these materials also contributes to a more sustainable approach to healthcare technology. I believe this project highlights history, technology, and human well-being, making it a valuable contribution to the scientific community and society as a whole.

 

 

Conclusion:

Our hypothesis was correct as carbon fibre did exceptionally better compared to polypropylene. When completing tests, carbon fibre gave greater stability, comfort, and durability; however, polypropylene gave more flexibility to perform. Carbon fibre had better test results. While they are decently similar in support braces, contrasting them into a mould together with a ratio that contains more carbon fibre, would be able to inherit some flexibility from polypropylene. In the running test, it's evident that wearing Carbon Fibre AFOs consistently achieved faster completion times compared to the Polypropylene AFOs. The Carbon Fibre trials ranged from approximately 48.87 to 58.71 seconds, whereas the Polypropylene trials ranged from approximately 1:02.45 to 1:09 minutes. This suggests that Carbon Fibre AFOs may offer better support and energy transfer during running activities, resulting in improved speed and efficiency. Similarly, in the jumping test, when I was wearing Carbon Fibre AFOs they consistently achieved longer jump distances compared to the Polypropylene AFOs. The Carbon Fibre trials ranged from approximately 1.89 to 2 meters, while the Polypropylene trials ranged from approximately 1.80 to 1.95 meters. This indicates that Carbon Fibre AFOs may provide greater stability and propulsion, allowing people to possibly generate more power and achieve higher jump heights.

 

 

By understanding the performance differences between these materials, individuals with ankle and foot issues can make informed decisions when selecting AFOs tailored to their specific needs and lifestyles. For instance, someone who leads an active lifestyle may choose Carbon Fibre AFOs for enhanced support during sports or physical activities, while those seeking comfort and flexibility for daily tasks may prefer Polypropylene AFOs. Ultimately, this research contributes to improving the quality of life for individuals with mobility challenges, empowering them to participate more fully in their daily activities with the right orthotic support.

Furthermore, it can assist with engineering for other necessities that need certain materials. Carbon fibre is gaining popularity and polypropylene is not looked upon as much but is also an important engineering material. For example, carbon fibre's properties include such strengths that it can help in creating cars because of the lightweight-to-strength ratio. Experimenting with these can help in the decision of engineering and discovering what is needed to yield the greatest statistics.

- Our experiment included a few mistakes when conducted

-  When experimenting, the AFOs used weren't the same size as one was used when Aydin was at a younger age. As he grew, his foot grew as well causing the AFO to be slightly tighter which caused a slight toll on the experiment. Although it is older, Aydin's foot grows at a slower pace due to his cancer.

- The experiment could have been conducted in multiple ways, but the cheaper and more simple option is to test with a human. Although a human could cause the results of the test to be less accurate, we compensated by adding more trials to make up an average for our tests.

- At the time of experimenting, I was not able to find sticky notes and had to compromise by using tape. The effects of this were not major but I feel like it would have been easier to complete the trials as the tape was double-sided and was sometimes stuck onto the fingers.

 

Comparison of Mechanical Properties of Carbon Fibre and ... - Avestia, avestia.com/MCM2021_Proceedings/files/paper/MMME/MMME_301.pdf. Accessed 22 Nov. 2023. 

G-Innovative (2022) What is carbon fiber?, Innovative Composite Engineering. Available at: https://www.innovativecomposite.com/what-is-carbon-fiber/#:~:text=A%20Brief%20History%20on%20Carbon,just%20outside%20of%20Cleveland%2C%20OH (Accessed: 21 November 2023). 

“Comprehensive Guide on Polypropylene (PP).” Polypropylene (PP) - Types, Properties, Uses & Structure, omnexus.specialchem.com/selection-guide/polypropylene-pp-plastic. Accessed 21 Nov. 2023. 

“Dragonplate: Engineered Carbon Fiber Composite Sheets, Tubes and Structural Components: Made in USA.” Dragon Plate, DragonPlate, dragonplate.com/a-brief-history-of-carbon-fiber. Accessed 21 Nov. 2023.  

Composites Construction UK, Joe. “Is Carbon Fibre a Sustainable Material for Strengthening Buildings and Structures?” Composites Construction UK, 24 Mar. 2022,  

www.fibrwrap-ccuk.com/carbon-fibre-strengthening/is-carbon-fibre-a-sustainable-material-for-strengthening-buildings-and-structures/#:~:text=Carbon%20fibre%20is%20not%20currently,make%20new%20products%20or%20items. 

https://www.britannica.com/science/polymer/Synthetic-polymers  

 

 

I'd like to express my gratitude to the doctors who provided the AFOs used in this experiment. Their support and cooperation were very important in conducting this research. Additionally, I extend my appreciation to my teacher, Ms. Burkell, for her insightful suggestions and guidance on what we could improve, which contributed to making this project higher-quality.