*Article* **Effect of Composition Strategies on Mycelium-Based Composites Flexural Behaviour**

**Adrien Rigobello \* , Claudia Colmo and Phil Ayres**

Centre for IT and Architecture, Royal Danish Academy, 1435 Copenhagen, Denmark; ccol@kglakademi.dk (C.C.); phil.ayres@kglakademi.dk (P.A.)

**\*** Correspondence: arig@kglakademi.dk

**Abstract:** Mycelium-based composites (MBC) are a promising class of relatively novel materials that leverage mycelium colonisation of substrates. Being predicated on biological growth, rather than extraction based material sourcing from the geosphere, MBC are garnering attention as potential alternatives for certain fossil-based materials. In addition, their protocols of production point towards more sustainable and circular practices. MBC remains an emerging practice in both production and analysis of materials, particularly with regard to standardisation and repeatability of protocols. Here, we show a series of flexural tests following ASTM D1037, reporting flexural modulus and flexural modulus of rupture. To increase the mechanical proprieties, we contribute with an approach that follows the composition strategy of reinforcement by considering fibre topology and implementing structural components to the substrate. We explore four models that consist of a control group, the integration of inner hessian, hessian jacketing and rattan fibres. Apart from the inner hessian group, the introduction of rattan fibres and hessian jacketing led to significant increases in both strength and stiffness (*α* = 0.05). The mean of the flexural modulus for the most performative rattan series (1.34 GPa) is still close to three times lower than that of Medium-Density Fibreboard, and approximately 16 times lower in modulus of rupture. A future investigation could focus on developing a hybrid strategy of composition and densification so as to improve aggregate interlocking and resulting strength and stiffness.

**Keywords:** mycelium-based composite; biomaterials; natural composites
