MIT Researchers 3D Print Structural House Components from Recycled Plastic

Engineers at the Massachusetts Institute of Technology (MIT) have developed a method for producing structural elements for house construction, such as beams and roof trusses, from recycled plastic using 3D printing. The approach aims to kill two birds with one stone: it should reduce the use of wood and thus deforestation, and make meaningful use of plastic waste to make house construction more sustainable.

MIT researchers estimate that by 2050, about one billion new homes will need to be built worldwide. If timber frameworks, as used in many parts of the world, were used for their basic structures, an area the size of the Amazon rainforest would have to be deforested. To avoid this, the researchers have chosen to replace load-bearing basic elements of house construction made of wood with modular elements made of recycled plastic, as they write in the study “Design, Manufacture and Testing of Structural Trusses using Additively Manufactured Polymer Composites“ (PDF), which was published in the Solid FreeForm Fabrication Symposium Proceedings.

For their experiments, the MIT engineers first developed an alternative floor truss. Traditionally, such a truss consists of wooden beams connected with diagonal and parallel support structures, thus achieving its stability. A floor, also made of wood, is then applied to this.

Lightweight and Stable Structural Elements

The researchers developed a structure that promised high load-bearing capacity. The basic elements for this were printed from recycled plastic using an industrial 3D printer. The engineers assembled four truss structures from the approximately 2.4 m long, 2.5 cm wide, and 30 cm high elements. Their load-bearing capacity was about 1814 kg, thus exceeding the building codes of the US Department of Housing and Urban Development. The individual plastic parts weigh only 5.9 kg, making them significantly lighter than comparable structural elements made of wood. Production using an industrial large-format 3D printer is possible in just 13 minutes.

Encouraged by the results, the MIT team intends to design and print further structural elements for house construction to create a complete structural frame for a small house.

So far, the scientists have used plastics for 3D printing that have been pre-sorted and cleaned for the recycling process. The plastic pellets used consist of a mixture of PET and glass fiber to combine good printability with high durability. However, such plastics are expensive. To ensure that the plastics used in house construction achieve a competitive price compared to wood, the scientists intend to use contaminated plastics in the future, for example from used PET bottles. However, how such contamination can affect the strength of the elements for house construction still needs to be investigated more closely. The researchers are confident, however, that the resulting problems can be solved to create lightweight and therefore easily transportable components on an industrial scale.

(olb)