Hygro-thermal coupling on 4D-printed biocomposites as key for meteosensitive shape-changing materials

Abstract

Hygromorph BioComposites (HBC) exhibit shape-changing actuated by a moisture content (MC) variation due to their bilayered bioinspired architecture. However, their application in daily meteorologic variation is limited due to relative humidity (RH) and thermal couplings. This work aims to investigate the role of temperature variation on the shape changing of 4D printed continuous flax fibres reinforced HBC so that ThermoHygromorph BioComposites (THBC) are introduced. The responsiveness of the THBC is governed by the MC of the material and the stiffness ratio between the passive and active layer, which are both thermally dependant. An increase in temperature strongly reduces the actuation amplitude while the actuation kinetics is strongly fastened. A 4D-printed HBC structure is designed and submitted to a practical outdoor environmental loading, to understand the impact of daily RH and temperature variations on THBC actuation.