Study of mechanical properties of 3D printed PLA+HA composite manufactured through different methods

Author(s): Violetta Rostobaya

Mentor(s): Dr. Ali Beheshti, Mechanical Engineering

Abstract
PLA polymer is one of the most widely used materials in 3D manufacturing industry. Pure PLA has limited mechanical and tribological properties; however they can be enhanced by adding nanocomposites such as Hydroxyapatite (HA). Even as small portions as 1wt% of HA can make PLA brittle, durable and biocompatible, which is advantageous for biomedical applications like inner body bone and join prosthetics. The mixing manufacturing method is also a factor in achieving highest quality of resulted composite material. The objective of this research is to outline which out of four manufacturing methods: wet mixing, dry speed mixing, magnetic stirring and dry mixing is the most effective in yielding most desirable mechanical properties. Wet mixing and magnetic stirring methods require to liquefy PLA with DCM dissolvent and then add HA into the mixture. Dry speed mixing and dry mixing require dry PLA pellets to be mixed with HA powder. The filament for each of methodologies is prepared with extruder and is used to 3D print testing samples. After manufacturing is finished, the samples are tested for roughness, strength, young’s modulus, hardness, compression, creep, scratch and wear. The testing methodologies are profilometry, indentation, compression tests and SEM scanning. Based on analyzed data the conclusion is drawn about effectiveness of manufacturing method.
Audio Transcript
My name is Violetta Rostobaya, I am a senior mechanical engineering student and I do undergraduate research under mentorship of Dr. Ali Beheshti. I work on my research in the tribology and surface mechanics lab located at innovation drive at Sci tech campus of George mason university. The topic of my research is Effect of different manufacturing methods on mechanical and tribological properties of 3D printed PLA and HA.

The goal of my research is to study mechanical properties of common 3D printing polymer PLA in composition with biomaterial hydroxyapatatite or HA. The reason why engineers want to fuse PLA with HA is to enhance mechanical properties of the polymer, make it stronger, more brittle, so that it can withstand high loads under compression. PLA in combination with HA are commonly used in biomedical applications for producing prosthetic bones and joints, which is why we want to make material as strong as possible, but also light and porous, so that it imitates structure of a real bone.

There is a nuance of how two components are mixed, since the manufacturing method is also a factor in the quality of the produced material. The differences of the methods in my research are how fast we can mix two components (fast or slow) and in what state PLA is in (liquid or solid), so the total amount of methods are four. For fast or speed mixing I use speed mixer and for slow mixing I use magnetic stirrer. To achieve solid state of PLA no actions are required: PLA already comes in form of solid pellets, and to achieve liquid state, PLA is dissolved using very strong dissolvent called DCM. The proportions of HA to PLA is 1%, usually mixed as 2 grams of HA to 18 grams of PLA.

After the materials for all four methods are ready, they are fed into the extruder machine, which shapes the polymer into filament through melting the plastic material at a high temperature of 180 Celsius degrees. The filament then is used to 3D print the samples shaped as rectangular cuboid with sides of 1 by 1 by 2 inches for indentation and compression testing.

The results of this research will show which manufacturing method is the most successful and effective in yielding the desired properties and hopefully will contribute to the knowledge of growing and expanding 3D printing technology.

I would like to thank you everyone who supported me while I was working on this project including Dr. Beheshiti, Dr. Bagheri, Dr. Lee and Office of Student Scholarships, Creative Activities and Research.

Thank you for watching and I hope this video was informative!

One reply on “Study of mechanical properties of 3D printed PLA+HA composite manufactured through different methods”

Thank you for sharing your work, Violetta. I look forward to hearing more about progress toward 3D printing of material that could substitute for bone. What is the next step?

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