Electrostatic adhesion for added functionality of composite structures

Abstract

Electrostatic adhesion can be used as a means of reversible attachment. The incorporation of electrostatic adhesion into fibre reinforced polymer (FRP) composite structures could provide significant value added functionality. Imparting large potential differences (~ 2 kV) across electrodes generates an attractive force, thus providing a means of attachment. This could be used as a reversible latching mechanism or as a means of controllable internal connectivity. Varying the connectivity for discrete elements of a substructure of a given design allows for control of internal load paths and moment of area of the cross section. This could facilitate variable stiffness (both in bending and torsion). Using a combination of existing fabrication techniques, functional electrodes have been integrated within a FRP. Copper polyimide thin film laminate material has been both co-cured with carbon fibre reinforced epoxy (CFRP) and bonded to PVC closed cell foam core material to provide a range of structural configurations with integrated electrodes. The ability of such integrated devices to confer variations in global bending stiffness of basic beam structures is investigated. Through the application of 4 kV across integrated electrostatic adhesive devices, a 112% increase in flexural stiffness has been demonstrated for a composite sandwich structure.

Interlocking electro-bonded laminates

“…The 1 kV data is far below the expected shear holding force levels. This is in line with some existing literature, where the 1 kV values also fell below the expected values, whereas higher voltage results matched the theoretical values more closely (Heath et al, 2016a).…”

“…For the overall core width of 30 mm, and a maximum core thickness of 6 mm (geometric restrictions for direct comparison to a previous study (Heath et al, 2016a)), a range of amplitudes and wavelengths were considered. Table 1 shows the resulting change in length from the 30 mm standard width.…”

“…The shear holding force is of greatest interest, as this determines the level of shear stress transfer between the upper and lower elements (Heath et al, 2016a), and when subject to a tensile force in the x-direction, the resistance to sliding is determined by the product of the surface friction coefficient and the total electrostatic adhesive force. The interlocking EBL devices were fabricated by means of a relatively simple modular process.…”

Morphing hybrid honeycomb (MOHYCOMB) within situPoisson’s ratio modulation

“…Figure 9 shows the values found along with a comparison to those values expected using Eq. 2, assuming an air gap of 3.5 µm (from previous research [5]. Recall that the double lap shear joint allows for the integration of two discrete electrostatic adhesive interfaces, doubling the electrode contact area.…”

“…The application of a large potential difference across the integrated electrodes generated a significant holding force, allowing for increased shear stress transfer across the electroadhesive interface, thereby increasing the global bending stiffness of the structure. Heath et al investigated the operation of these devices under higher applied loading, demonstrating improved functionality from a fabrication method which resulted in closer electrode spacing [5]. From the work of Di Lillo et al, the high levels of achievable holding force are clear, particularly for less rigid electrode elements [6].…”