Additive manufacturing of an electrically triggered actuator: electro-thermo-mechanical behaviour of a carbon black/polylactic acid composite
Topic(s) : Manufacturing
Co-authors :
Laurane ROUMY (FRANCE), Thuy-Quynh TRUONG-HOANG (FRANCE), Damien MARCHAND , Fabienne TOUCHARD (FRANCE), Francisca MARTINEZ-HERGUETAAbstract :
4D printing combines 3D printing with a smart material reacting to an external stimulus, time being the fourth dimension. This technology finds applications in soft robotics, medicine, and space exploration for instance [1]. Thermally activated Shape Memory Polymers (SMP) are often used because of their ability to shift shape to a pre-programmed configuration when heated above their glass transition temperature. Amongst various 3D printing techniques, Fused Filament Fabrication (FFF) is commonly used to manufacture 4D printed devices with SMPs [2]. In particular, conductive carbon black reinforced polymers that are able to heat thanks to Joule effect are of great interest for 4D printing. In a previous article, the effects of the printing parameters on the electro-thermal properties of 3D printed carbon black/polylactic acid (CB/PLA) composites were determined [3]. In this study, the coupling between the electrical, thermal and mechanical properties of 3D printed CB/PLA composites is investigated by multi-instrumented tensile tests to design an electrically triggered 4D printed actuator.
Rectangular samples of CB/PLA composites were 3D printed with different raster angles and stacking sequences. Multi-instrumented tensile tests were then performed to measure the mechanical properties and electrical resistance evolution of the specimens. In particular, results showed the complex resistivity evolution in unidirectional longitudinal samples under tensile loading (Fig.1). In addition, repeated progressive tensile tests, acoustic emission, SEM, and micro-CT results highlighted the development of crazes, especially after surpassing 80% of the elongation at break of the specimens.
An actuator prototype was then designed by printing a composite structure with the filaments aligned along the electricity path. The 4D printing process involves two main steps: a programming step of the temporary shape by heating the actuator thanks to Joule effect, folding it at a 90° angle, and cooling it down; and a triggering step where the actuator is electrically heated again to recover its initial shape with a 0° angle. Figure 2 depicts the recovery ratio evolution of the composite structure with different folding methods. The recovery ratio was calculated by comparing the angle after the shape recovery and the initial one. The folding process has a significant impact on the recovery ratio, with the second row of trials more than doubling it. Work is in progress to optimise the recovery ratio of this composite actuator for reliable 4D printed devices.
Acknowledgements
This works was supported by the Defense Innovation Agency (AID) of the French Ministry of the Armed Forces through the grant [AID-2021 65 0045].
Rectangular samples of CB/PLA composites were 3D printed with different raster angles and stacking sequences. Multi-instrumented tensile tests were then performed to measure the mechanical properties and electrical resistance evolution of the specimens. In particular, results showed the complex resistivity evolution in unidirectional longitudinal samples under tensile loading (Fig.1). In addition, repeated progressive tensile tests, acoustic emission, SEM, and micro-CT results highlighted the development of crazes, especially after surpassing 80% of the elongation at break of the specimens.
An actuator prototype was then designed by printing a composite structure with the filaments aligned along the electricity path. The 4D printing process involves two main steps: a programming step of the temporary shape by heating the actuator thanks to Joule effect, folding it at a 90° angle, and cooling it down; and a triggering step where the actuator is electrically heated again to recover its initial shape with a 0° angle. Figure 2 depicts the recovery ratio evolution of the composite structure with different folding methods. The recovery ratio was calculated by comparing the angle after the shape recovery and the initial one. The folding process has a significant impact on the recovery ratio, with the second row of trials more than doubling it. Work is in progress to optimise the recovery ratio of this composite actuator for reliable 4D printed devices.
Acknowledgements
This works was supported by the Defense Innovation Agency (AID) of the French Ministry of the Armed Forces through the grant [AID-2021 65 0045].