Morphing a carbon fibre composite with only 1.5 V
Figure 1 A carbon fibre composite laminate that uses lithium-ions to change shape. (1) When both layers have the same concentration of lithium the laminate is flat. (2) When a current is applied, lithium ions move out of the bottom carbon fibre layer, which contracts, and into the top carbon fibre layer, which expands. This creates a bending motion. (3) By reversing the current the laminate bends in the other direction.
This article is written by Wilhelm Johannisson, Ross Harnden, Dan Zenkert and Göran Lindbergh, all at the Royal Institute of Technology, KTH in Stockholm
Our latest research article demonstrates a new material concept: a shape-changing carbon fibre composite material, that is lightweight, has a stiffness higher than aluminium, and is electrically controlled.
Structures that can change shape are advantageous in a variety of applications such as aerospace, renewables, and robotics. The problem with current shape-changing technologies is that they are either heavy, lack mechanical stiffness or are hard to control. This limits their use in weight-sensitive applications. We demonstrate a material concept that paves the way for a new class of lightweight, stiff, solid-state morphing materials. Future applications could include the trimming of aerodynamic surfaces for steady-state conditions in aircraft and wind turbines, and deployment of satellite booms.
The material is made from two layers of carbon fibre separated by a thin sheet of ceramic polymer. These three layers are then embedded in a solid battery electrolyte matrix that can transfer both lithium ions and mechanical load. In this way the material resembles typical carbon fibre composite laminates that are already used in many applications, from hockey sticks to aircraft and space structures.
The process for creating the morphing is very similar to the charging and discharging of an ordinary lithium-ion battery. When carbon fibres are charged with lithium, they expand, and when they discharge they contract. By charging one carbon fibre layer, while discharging the other a bending motion is created, since the charging layer expands while the discharging layer contracts. The charge/discharge process is carried out using low currents and low voltages (less than 1.5 V). Our article demonstrates this concept experimentally with numerical modelling giving a good correlation with our experimental observations.
The research has been conducted by KTH researchers Wilhelm Johannisson and Ross Harnden (both members in the LIGHTer PhD network), together with Professors Dan Zenkert (member in the LIGHTer Academy) and Göran Lindbergh. All are members of the Swedish research group KomBatt whose interdisciplinary research focusses mainly on structural power composites.
Article access: The article entitled Shape-Morphing Carbon Fiber Composite using Electrochemical Actuation will be published during week 13 in the scientific journal Proceedings of the National Academy of Sciences and will be publicly accessible online at www.pnas.org/cgi/doi/10.1073/pnas.1921132117. Embargoed copies of the article will be available to journalists starting Wednesday, March 18, 2020, through EurekAlert!: https://www.eurekalert.org