Project in the Spotlight: Engineering Circular Sandwich Structures with Mycelium

Key information

Project title: MOLIERE: DevelopMent of biOlogicalLy-Inspired sandwich structurEs for aeRospacE applications
Project in the Spotlight: T24003
Funding: PPS-funded via TKI High Tech Systems and Materials
Research partner: TU Delft

The aerospace sector is facing growing circularity challenges. A major challenge is that aircraft interiors depend heavily on lightweight sandwich structures based on aramid honeycomb cores and fibre-reinforced composites. These materials provide excellent stiffness-to-weight performance, but they are also complex to manufacture, difficult to recycle, and largely derived from fossil resources. As the industry moves towards its 2050 net-zero ambitions, finding more sustainable alternatives has become increasingly important.

At TU Delft’s Shaping Matter Lab, researchers are exploring how biologically fabricated materials can be engineered for lightweight structural applications. Within the MOLIERE project, the team investigated whether fungal mycelium, the filamentous root-like network of fungi, could enable circular sandwich composite cores for aircraft interiors. Through its filamentous growth behaviour, mycelium can form lightweight, interconnected networks when grown on renewable nutrient substrates. This offers a fundamentally different route towards manufacturing circular composite cores.

From biological growth to engineered structures
Mycelium composites are produced by allowing fungal mycelium to colonise and bind nutrient-infused wood-derived substrate grains into a lightweight scaffold. While such materials have attracted growing interest in packaging and insulation applications, their use in high-performance engineering structures remains largely unexplored.

One of the central challenges is that biological growth is inherently variable. For aerospace applications, however, structural performance must be predictable, repeatable, and tunable for different load conditions. MOLIERE therefore focused not only on developing a bio-based material, but also on creating an engineering framework capable of translating fungal growth behaviour into controllable structural performance.

To achieve this, the project combined computational modelling, experiments, and fabrication into a multiscale design approach spanning micro, meso, and macro scales.

At the microscale, computational models simulated environmentally responsive mycelial growth under different nutrient and growth conditions. At the mesoscale, the team linked local growth density and substrate morphology to effective stiffness and material behaviour. These relationships were then upscaled to design functionally graded sandwich panels, where stiffness and weight could be tailored locally by varying substrate grain size.

Designing and fabricating a full-scale demonstrator
The optimised design workflow was translated into the fabrication of a full-scale demonstrator panel. To manufacture the panel, the researchers developed a repeatable growth and processing protocol using mould-based fabrication.

A sterilised mould containing laser-cut contour inserts defined the different grading regions within the panel. Pre-inoculated substrate grains were placed into the mould and incubated under controlled temperature and humidity conditions for 10–20 days, allowing the mycelium to colonise and bind the structure. The panel was then oven-dried to halt biological activity and stabilise the final geometry.

The resulting demonstrator showed that mycelium-based sandwich cores can be manufactured at structurally relevant dimensions while maintaining controlled grading and lightweight construction.

“At the Shaping Matter Lab, we are interested in how the growth of organisms can become part of the engineering design process,” says the project leader, Prof. Kunal Masania. “The project was not simply about replacing one material with another, but about understanding how biological growth can be translated into spatially controllable microstructures which influence the structural performance.”

Towards circular sandwich composites
MOLIERE demonstrated a validated modelling-to-manufacturing workflow for designing mycelium-based sandwich cores for representative aircraft interior load cases. The project also established a practical manufacturing route for producing functionally graded cores with tunable stiffness and density distributions.

Beyond lightweight performance, the project explored how such materials could contribute to more circular product systems. Because the core material is grown from renewable feedstocks and is compatible with bio-based recovery routes, it offers potential alternatives to conventional multi-material core systems that are difficult to recycle or recover at end of life.

At the same time, the project highlighted the challenges that remain before such materials could move closer to industrial implementation. Questions around qualification-relevant testing, repeatability, moisture sensitivity, fire performance, and large-scale manufacturing still require further investigation.

Nevertheless, MOLIERE demonstrates how biological growth can be integrated into engineering design workflows for future lightweight composite structures.