4D-printing of continuous flax fibre (cFF) reinforced biocomposites: toward tubular hygro-sensitive actuators
Topic(s) : Manufacturing
Co-authors :
Melvin JOSSELIN (FRANCE), Noëlie DI CESARÉ , Mickael CASTRO (FRANCE), Fabrizio SCARPA , Antoine LE DUIGOU (FRANCE)Abstract :
In recent years, 4D-printing has emerged as a relevant technology for the development of new smart materials and adaptative/multifunctional structures. Hygromorph Biocomposites (HBCs) belong to a specific class of smart materials able to exhibit a shape-changing response to surrounding relative humidity variations [1]. These smart materials take inspiration from several biological hygromorph actuators with specific seed dissemination ability such as pine cone or wheat awn [2]. In contrast to many materials used for 4D-printing, HBCs, and specifically continuous flax fibre (cFF) reinforced HBCs exhibit strong mechanical properties which make them suitable for semi-structural applications.
Most of the works related with 4D printing investigates 2D-to-3D shape-changing structures. The mostly linear bending motion generated by 4D printed flat beams is not particularly suitable for practical applications. Furthermore, for a same volume, a coil configuration is way more efficient to produce work than a flat beam configuration [3]. Although 3D printing offers significant design possibilities, the logic of adding material layer-by-layer makes the 4D-printing of 3D-to-3D shape-changing structures challenging. Especially, the printing of cFF reinforced filament faces particular constraints and geometric limitations that make out-of-plane printing difficult [4]. Thus, with a regular 3D-printer, the design window of cFF reinforced HBC is mainly limited to flat structures.
Inspired from the work of Van Manen et al. [5], a modified 3D-printer, allowing to print on a cylindrical surface, and equipped with a tailored nozzle for printing of cFF reinforced filament, has been developed (Figure 1a). This original printer opens the door to exploring the design window of new cylindrical or tubular topologies unprintable on conventional printers. The actuating capabilities of the 4D-printed structures are estimated by measuring the rotation and torque (i.e. the work) generated during a conditioning from a dry (0%RH) to a humid (90%RH) environment (Figure 1b). A finite element method (FEM) simulation, which is validated by previous experimental results, is used to compute the actuation (i.e. rotation and torque) of a 4D-printed structure in response to a given environmental stimuli (Figure 1c). A parametric optimization method is then implemented to determine the optimized structural parameters, that will lead to a programmed actuation responding to a desired application.
Thus, this study aims to develop programmable 4D-printed tubular actuators exhibiting a desired actuation in response to environmental relative humidity variations. Further investigations about tubular actuators exhibiting a wider range of shape-changing actuation (elongation, bending) could be discussed.
Most of the works related with 4D printing investigates 2D-to-3D shape-changing structures. The mostly linear bending motion generated by 4D printed flat beams is not particularly suitable for practical applications. Furthermore, for a same volume, a coil configuration is way more efficient to produce work than a flat beam configuration [3]. Although 3D printing offers significant design possibilities, the logic of adding material layer-by-layer makes the 4D-printing of 3D-to-3D shape-changing structures challenging. Especially, the printing of cFF reinforced filament faces particular constraints and geometric limitations that make out-of-plane printing difficult [4]. Thus, with a regular 3D-printer, the design window of cFF reinforced HBC is mainly limited to flat structures.
Inspired from the work of Van Manen et al. [5], a modified 3D-printer, allowing to print on a cylindrical surface, and equipped with a tailored nozzle for printing of cFF reinforced filament, has been developed (Figure 1a). This original printer opens the door to exploring the design window of new cylindrical or tubular topologies unprintable on conventional printers. The actuating capabilities of the 4D-printed structures are estimated by measuring the rotation and torque (i.e. the work) generated during a conditioning from a dry (0%RH) to a humid (90%RH) environment (Figure 1b). A finite element method (FEM) simulation, which is validated by previous experimental results, is used to compute the actuation (i.e. rotation and torque) of a 4D-printed structure in response to a given environmental stimuli (Figure 1c). A parametric optimization method is then implemented to determine the optimized structural parameters, that will lead to a programmed actuation responding to a desired application.
Thus, this study aims to develop programmable 4D-printed tubular actuators exhibiting a desired actuation in response to environmental relative humidity variations. Further investigations about tubular actuators exhibiting a wider range of shape-changing actuation (elongation, bending) could be discussed.