3D printing of wood and mycelium composites
In an article recently published in the open access journal Biomimeticsresearchers presented the preparation of wood veneer reinforced mycelium composites for durable building components.
Study: Wood veneer reinforced mycelium composites for durable building components. Image Credit: Cheng Wei/Shutterstock.com
The construction industry has been challenged in recent decades by the steady growth in population and the related demand for homes and building materials. At the same time, the additional pollution, energy and waste generated by the production of traditional building materials like cement, steel and plastics pose serious environmental risks.
The processing of materials widely used in the construction industry produces the majority of greenhouse gas (GHG) emissions. The depletion of natural resources and increased awareness of climate change have prompted researchers and companies to seek sustainable alternatives to materials currently in use.
The 4R concept of Reduce, Reuse, Recycle and Recover is becoming increasingly popular across industries as a way to reduce waste and encourage circular economy models. Cultivating biological materials from industrial factory waste could be a viable alternative.
Among these, the recent introduction of bio-based composite materials based on mycelium has the potential to change the construction industry. However, its low tensile and flexural strength is one of the most important constraints to its use in the construction industry. Wood, on the other hand, has long been known for its structural strength. Due to its fiber arrangement, it is a naturally tensile material.
Robotic fiber laying process with processed willow strips from the research project TETHOK—Textile Tectonics for Wood Construction, University of Kassel. Image Credit: Özdemir, E et al., Biomimetics
About the study
In this study, the authors focused on the use of unique robotic additive manufacturing procedures to improve the structural performance of mycelial composites for interior use by incorporating continuous wood fibers into the mycelial matrix as reinforcement.
Through physical prototyping and testing, two methodologies were investigated and their effectiveness, advantages and limitations were assessed. A hybrid fabrication method for this composite material system was developed and the samples were structurally tested to see how compression and reinforcement affect the strength of the composite.
Researchers combined the advantages of each material by utilizing the inherent characteristics of mycelium and wood veneer, as well as investigating the development of unique 100% bio-based wood veneer and mycelium composites with superior mechanical properties.
Compression with heat and pressure, as well as the incorporation of topologically engineered reinforcement inside the mycelium matrix, were the two approaches used to improve the strength of the material. The fundamental mechanical properties of this new composite were studied by structural tests on physical prototypes. Compressive strength, flexural properties and bond strength were investigated on test specimens fabricated with several versions of veneer mesh as reinforcement systems.
The team used Ganoderma lucidum and hemp for mycelium growth, as well as maple veneer for strength. The unreinforced samples were compared to the veneer-reinforced samples in pull-out, compression, and three-point bending tests. The tensile strength of the reinforcing joints was also tested.
The potential advantages of combining the distinct material properties of wood veneer and mycelium, as well as methods for the design and production of architectural components were discussed, and the results of preliminary experiments showing the effect of veneer reinforcements on increased flexural strength have been shown. The objective was to find strategies to increase the structural performance of this composite for architectural applications while maintaining acceptable levels of acoustic performance.
Robotic fiber laying process: (a) Laying fibers in one direction; (b) Fiber laying in direction two; (vs) 2D network completed. Image Credit: Özdemir, E et al., Biomimetics
A unique composite material based on mycelium derived from wood veneer as a green and sustainable alternative to traditional building materials with suitable applications in the construction industry has been successfully developed. Both procedures for improving the flexural strength of given composites by combining compression and a topologically designed veneer mesh with pressure and heat have been shown to be effective.
It has been discovered that the density and layout of veneer meshes as reinforcement systems are inextricably linked. A single layer of the low-density veneer mesh placed in the center of the mycelial block produced the best results for lightweight blocks.
The high-density lattice and the two low-density lattices at the top and bottom of the block helped to increase the bending strength of the block from about 0.17MPa to 0.19MPa, while the bending strength of the unreinforced block was slightly lower, about 0.16 MPa and 0.13 MPa, respectively. Shear failure occurred in samples with two low density networks, which had poor flexural strength and elastic modulus.
The dense panels with a low density lattice in the center followed the same pattern as the lightweight blocks and increased the flexural strength to more than twice that of the unreinforced dense panels, from about 10 MPa to 25 MPa. Compared with the unreinforced dense panels, the dense panels having a high-density lattice in the center showed no significant change in flexural strength. Comparing the two approaches, thick boards had higher overall bending strength.
3D trellis layout studies (dimensions in mm). Image Credit: Özdemir, E et al., Biomimetics
In conclusion, this study elucidated that the resulting unique wood veneer reinforced mycelium composite was 100% bio-based. The reinforced samples had better flexural strength and the reinforcement joints were stronger than the material itself.
The authors pointed out that dense panels reinforced with a single low-density mesh are best suited for applications requiring flat components and greater resistance to bending, and that lightweight blocks reinforced with a single low-density mesh would be acceptable. for more complex designs that do not require significant bending strength.
They mentioned that this study offered the fundamental material inputs for the large-scale development of the system and that the next step would be to create a numerical model that combines material properties, geometric variations and acoustic analyzes to optimize and evaluate various options. of design within the same digital system. computer framework.
They also believe wood veneer reinforced mycelium composites could be a potentially green and sustainable alternative to traditional building materials with architectural applications.
Özdemir, E., Saeidi, N., Javadian, A., et al. Wood veneer reinforced mycelium composites for durable building components. Biomimetics 7(2) 39 (2022). https://www.mdpi.com/2313-7673/7/2/39