Statistical Analysis of the Tensile Properties and Effect of Fill Density in Various Polymers Processed through 3D Printing Luke Buckner YSP Student CURENT Young Scholars Midterm 13 July 2015 Min Kao Building, University of Tennessee

Introduction Additive Manufacturing (i.e. 3D Printing) Using various materials such as metals, polymers, concrete and even human tissue Multiple Techniques SLA (Stereolithography) FDM (Fused deposition modeling) MJM (Multi-jet modeling) 3DP (Three dimensional printing) SLS (Selective laser sintering) AM is being used to fabricate end-use products in aircraft, dental restorations, medical implants, automobiles, and even fashion products. Aerospace, Automotive, electronics, Boeing Phantom Ray SLA: Very high end technology utilizing laser technology to cure layer-upon-layer of photopolymer resin (polymer that changes properties when exposed to light). FDM: Process oriented involving use of thermoplastic (polymer that changes to a liquid upon the application of heat and solidifies to a solid when cooled) materials injected through indexing nozzles onto a platform. MJM: incorporates hundreds of small jets to apply a layer of thermopolymer material, layer-by-layer Much like an inkjet printer 3DP: This involves building a model in a container filled with powder of either starch or plaster based material. An inkjet printer head shuttles applies a small amount of binder to form a layer SLS: utilizes a high powered laser to fuse small particles of plastic, metal, ceramic or glass.

Background/Objectives To study PLA, ABS, and Bio-ABS using the FDM techniques for their mechanical (tensile) properties To study the effect fill density on elastic modulus and ultimate strength Following ASTM (American Society for Testing and Materials) standards

Designing the test specimen in CAD Methodology Designing the test specimen in CAD Designed in Solidworks following ASTM standards CAD → STL→ G-Code Left: A rendering of the specimen in CAD Right: ASTM Standards dimensions for polymer testing

Printing and Testing the Specimens Methodology Printing and Testing the Specimens Printer: Lulzbot Mini Tester: Instron APEX 60UD Left: The specimens being printed Above: An ABS specimen fractured on the tensile tester

Results Stress-Strain Curves for PLA, ABS, Bio-ABS Elastic Modulus (Young’s Modulus) for PLA, ABS, Bio-ABS

Results cont.

Analysis of Results Stress-strain curves of ABS at varying fill densities

Conclusions Using 3-D printing, three different polymers were successfully processed and tested for mechanical properties. The PLA exhibits highest strengths among three polymers under the given processing and test conditions. ABS and Bio-ABS show very comparable mechanical properties. The effect of fill density on mechanical properties is clearly shown in that both modulus and strength increased linearly with density.

Acknowledgements This work was supported primarily by the ERC Program of the National Science Foundation and DOE under NSF Award Number EEC-1041877. Other US government and industrial sponsors of CURENT research are also gratefully acknowledged.

Questions and Answers

ABS

ABS 60% & 100%

Bio-ABS

PLA