Mechanics of bio-based uniaxially thermoformed polyurethane foams with zero and negative Poisson’s ratio

Uniaxial thermoforming compression is a promising technique for producing Zero and Negative Poisson’s Ratio (ZPR/NPR) open-cell foams. It allows for faster, easier, and more scalable production. The sustainability credentials of this method can be further improved by exploiting bio-based (i.e., from vegetable oils) open-cell polyurethane foams to generate porous and sustainable metamaterials. This work investigates the effect of manufacturing parameters (compression ratio, heating temperature and time) and compression direction on bio-based foam’s quasi-static and dynamic mechanical performance, converted through uniaxial thermoforming. ZPR behaviour was observed independently of processing parameters when thermoforming along the foam’s rise direction. NPR foams were, however, obtained when thermoforming occurred perpendicularly to the rise direction and the processing parameters were minimised. A two-level, three-factor full factorial experimental design was implemented for thermoforming along the foam’s rise direction. Results showed that the compression ratio mainly affected the material stiffness, whereas quasi-static energy dissipation strongly depended on heating temperature and time. NPR and ZPR foams presented suitable properties for tissue engineering and cushioning applications, further highlighting the potential of this manufacturing technique for use in bio-based porous substrates. • Extensive quasi-static and dynamic mechanical characterisation of bio-based polyurethane foams converted via uniaxial thermoforming process. • Zero Poisson’s Ratio is unaffected by the processing parameters (along the rise direction). • Stiffness is influenced by compression ratio; quasi-static energy dissipation is controlled by heating temperature and time. • Negative Poisson’s Ratio is obtained when thermoforming perpendicular to the foam’s rise direction.