Investigation of Mycelium Composite for Acoustical Ceiling Tile Application
Creators: name: Womer, Scott
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 401701
subject: Acoustics and noise control (excl. architectural acoustics)
classificationCode: 401602
subject: Composite and hybrid materials

description: Mycelium composites have gained considerable attention for their environmental credentials. While there is much public enthusiasm surrounding the material, it has struggled to find widespread adoption. Packaging has been mycelium composites most successful application, but it remains niche and expensive. Mycelium composites have been considered for many construction applications such as brick, insulation, and boards, however these occupy an even smaller commercial niche and are mostly used artistically. Acoustic panels have gained growing commercial interest as they are non-structural and utilize mycelium composites’ good acoustic properties. However, acoustic ceiling tiles constructed of mycelium composites have yet to be researched given the higher product standards. This master’s research explores the feasibility of mycelium composites for use as an acoustic ceiling tile application. Feasibility is determined by characterizing mycelium composites’ strength and acoustic properties. Further, mycelium composites’ strength is explored by investigating spent brewer’s grain as an alternative substrate and hybridizing all sample types with hydrated gypsum. 

The testing explored in this research aims to capture the various strength and acoustic properties of mycelium composites specific to acoustic ceiling tiles. Strength testing includes flexural, hardness, friability, and humidity deflection. Strength tests identified the most suitable sample for acoustic testing. Then acoustic testing was conducted to characterize the materials at both normal and random incidence. To do this an impedance tube, a small sound reverberation room and the two cavity analysis were used. The Armstrong Ultima acoustic ceiling tile was used the commercial baseline. 

As mycelium composites are fabricated in a variety of ways, this research explored hybridization and substrates in the context of improving strength. For hybridization, samples were hybridized with hydrated gypsum at 10, 20 and 30 percent concentrations and tested for flexural and hardness strength. For substrates, spent brewer’s grain was examined in relation to the common hemp shive substrate and used in all strength tests but was not suitable for acoustic tests. All samples were then analyzed by computerized tomography and scanning electron microscopy. Together these results provide a complete picture of how one type of mycelium composite could perform as an acoustic ceiling tile. 

Results and analysis indicate that while mycelium composites can meet acoustic ceiling tile standards, they are impractical for this application. Compared to the Armstrong Ultima ceiling tile, mycelium composites are weaker in flexural and hardness strength but slightly better in friability and humidity deflection. Acoustically, mycelium composites can be good absorbers however results are inconsistent, and the material itself is difficult to be made consistently. Further hybridization with gypsum does little to improve strength and its cost is prohibits its use at a large scale. The manufacturing time required for each sample further reduces its practical usage. The general conclusion from the literature review is that hybridization does not improve mycelium composite strength compared to high preforming unhybridized samples. For substrates, the commercially preferred hemp shive is a far more suitable substrate than spent brewers grain. Overall, this research suggests mycelium composites have enough strength and acoustic performance for an acoustic ceiling tile application but are generally impractical due to inconsistent performance, low dimensional tolerances, long manufacturing time, and low hardness.