Three-dimensional printers Yongsan An and Woon-Ryeol Yu explored the improvement of three-dimensional printing by researching alternative materials. In the recently published "Three-dimensional Printing of Continuous Carbon Fiber Reinforced Shape Memory Polymer Composites", the mechanical performance challenges that plague many industrial users were discussed. In this article, we will look at how researchers can use composite materials to improve the mechanical properties of 3D printing.

In this study, researchers tried to use continuous carbon fiber reinforced shape memory polymer composites (SMPC) - Thermoplastics and thermosetting plastics in FDM 3D printing.

[Mechanical Properties of Continuous Fiber Reinforced Polymer Composites, Short Fiber Reinforced Polymer Composites and Polymer Matrix Prepared by FDM]

Researchers tested the parameters and printed samples to learn more about the advantages and limitations of smart materials such as SMP, which can change with the environment and then return to normal shape. This type of material is similar to 4D material, allowing users greater flexibility in a variety of applications. The team hopes to improve the manufacturing process with the addition of carbon composites.

The research team created a custom FDM 3D printer for the study to produce continuous fiber reinforced SMPC parts. Two different types of materials were selected for evaluation: PLA and polyurethane SMP filaments (as thermoplastic matrix) and SMP epoxy resin as thermosetting matrix. The team then added continuous carbon fibers to the filament for reinforcement.

[Diagram of 3D printing system for continuous carbon fiber reinforced polymer composites for (a) thermoplastics and (b) thermosetting plastics]

When they printed out the samples to be tested, they tested the differences in temperature and printing speed, and then the team assessed the mechanical and shape memory characteristics.

3D printing of CF and PLA composites. (a) Only PLA, (b) nozzles with a diameter of 1.5 mm and (c) nozzles with a diameter of 2 mm)

In the paper, the researchers write that "storage modulus (G'), loss modulus (G") and PLA viscosity decrease near their melting point. The storage modulus decreases at a rate greater than the loss modulus, which makes PLA have more liquid properties. Therefore, PLA can be easily extruded from nozzles at 180 C.

"The PLA filament without CF is extruded smoothly from the nozzle, whether its diameter is greater than the fusion area or not. However, for nozzles with a diameter of 1.5mm, PLA matrix is extruded, just like spirally wound CF. This is because PLA extrudes more than CF because CF is not stretched during extrusion. In addition, poor temperature and different extrusion speed lead to CF failure in the process of 3D printing. On the other hand, for a 2 mm diameter nozzle, PLA and CF are extruded directly because of the synchronization of extrusion speed.

There are many challenges, such as CF not fully coated with PLA. To better optimize the supply speed of PLA and CF, as well as the material structure and fusion time, researchers created an improved print head, which also added calendar volumes and appropriate tension devices.

The researchers said that the printed SMPC exhibited better mechanical properties in the fiber direction than the traditional 3D printing polymer.

Strength and stability of mechanical properties are a continuing challenge in 3D printing, but there is still room for improvement as researchers are determined to improve materials and processes for progressive manufacturing technologies ranging from carbon lattices to titanium and for checking biocompatibility.

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