Schematic top view of 3D printing (A). Feed chamber (F) and build chamber (B) are localized in x–y plane.
Schematic top view of 3D printing (A). Feed chamber (F) and build chamber (B) are localized in x–y plane.

German researchers have demonstrated that the mechanical properties of 3D-printed structures can be improved with the addition of fiber reinforcement.

Since entering the mainstream a few short years ago, 3D printing has grown from strength to strength, with systems now capable of printing everything from 3D chocolate shapes to titanium implants. But the technique’s origins in industrial rapid prototyping have not been forgotten, with companies across the globe using 3D printing to create complex components quickly and reliably.

Research from a team at University Hospital Würzburg in Germany has focused on improving one type of 3D printing - three-dimensional powder printing. Their results, published in Materials Letters 139 (2014) 165–168 (DOI: 10.1016/j.matlet.2014.10.065) show that a range of different short fibers can greatly improve the mechanical robustness of a final printed piece when compared to non-reinforced printed samples.

Three-dimensional powder printing (3DP) is used to create complex 3D structures by selective application of a liquid binder into a bed of powder, using an inkjet print head. As each successive thin layer of powder is similarly treated, a shape can be built up, with the excess powder removed in a process called "de-powdering". While 3DP benefits from accurate control and the ability to 3D print at room temperature, its application is often limited by the low mechanical strength of the printed samples.

The team, led by Uwe Gbureck, developed a fiber reinforcement approach similar to mineral bone cements used in orthopaedics and dentistry. A series of short (length 1–2 mm), commercially-available fibers were added to a matrix of cellulose-modified gypsum powder. Identical structures were produced with each of the reinforced powers, and the mechanical properties determined using a four-point bending test regime.

Even at low concentrations of 1 %w/w, it was found that structures produced using the reinforced powers outperformed those produced without fibers, in terms of both their green strength (resistance to deformation) and their fracture toughness. When short glass fibers were used, despite no increase in apparent density, the material’s flexural strength was significantly higher (up to 180%) than that of non-reinforced structures.

This work has demonstrated that reinforced powders may have a role to play in biomedical applications where strength is key. The next stage for Gbureck and his team is to extend their technique to biocompatible fibers. If they manage this, your next filling may be 3D-printed specifically for you.

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