Morphology and mechanics of fungal mycelium

We study a unique biomaterial developed from fungal mycelium, the vegetative part and the root structure of fungi. Mycelium has a filamentous network structure with mechanics largely controlled by filament elasticity and branching, and network density. We report the morphological and mechanical characterization of mycelium through an integrated experimental and computational approach. The monotonic mechanical behavior of the mycelium is non-linear both in tension and compression. The material exhibits considerable strain hardening before rupture under tension, it mimics the open cell foam behavior under compression and exhibits hysteresis and the Mullins effect when subjected to cyclic loading. Based on our morphological characterization and experimental observations, we develop and validate a multiscale fiber network-based model for the mycelium which reproduces the tensile and compressive behavior of the material.

Effect of filler geometry on interfacial friction damping in polymer nanocomposites

Single-walled carbon nanotube polycarbonate and C60 polycarbonate nanocomposites were fabricated using a solution mixing method. The composite loss modulus was characterized by application of dynamic (sinusoidal) load to the nanocomposite and the pure polymer samples. For a loading of 1 weight %, the single-walled nanotube fillers generated more than a 250% increase in loss modulus compared to the baseline (pure) polycarbonate. Even though the surface area to volume ratio and surface chemistry of C60 is similar to that for nanotubes, we report no significant increase in the energy dissipation for the 1% weight C60 nanoparticle composite compared to the pure polymer. We explain these observations by comparing qualitatively, the active sliding area (considering both normal and shear stresses) for a representative volume element of the nanotube and the nanoparticle composites. These results highlight the important role played by the filler geometry in controlling energy dissipation in nanocomposite materials.