Julie A Etches

Composite corrugated structures for morphing wing skin applications

Composite corrugated structures are known for their anisotropic properties. They exhibit relatively high stiffness parallel (longitudinal) to the corrugation direction and are relatively compliant in the direction perpendicular (transverse) to the corrugation. Thus, they offer a potential solution for morphing skin panels (MSPs) in the trailing edge region of a wing as a morphing control surface. In this paper, an overview of the work carried out by the present authors over the last few years on corrugated structures for morphing skin applications is first given. The second part of the paper presents recent work on the application of corrugated sandwich structures. Panels made from multiple unit cells of corrugated sandwich structures are used as MSPs in the trailing edge region of a scaled morphing aerofoil section. The aerofoil section features an internal actuation mechanism that allows chordwise length and camber change of the trailing edge region (aft 35% chord). Wind tunnel testing was carried out to demonstrate the MSP concept but also to explore its limitations. Suggestions for improvements arising from this study were deduced, one of which includes an investigation of a segmented skin. The overall results of this study show that the MSP concept exploiting corrugated sandwich structures offers a potential solution for local morphing wing skins for low speed and small air vehicles.

Development of a self-actuating fibre reinforced ionic epoxy gel polymer composite

This paper investigates the potential for using epoxy hydrogels with the addition of fibre reinforcement as a self-actuating fibre reinforced polymer composite. The aim of adding fibre reinforcement is to improve the structural performance whilst maintaining the actuation potential of the system. This study has also investigated the role and function of distributed fibrous electrodes in optimizing the magnitude and rate of self-actuation. It was found that the inclusion of two-dimensional fibre reinforcement altered the actuation response of the hydrogel from a three-dimensional shape change to an orthotropic response with the actuation concentrated in the through thickness direction. Various arrangements of the fibrous electrodes proved successful in enabling actuation. A rudimentary demonstrator was constructed and tested.

The manufacture of honeycomb cores using Fused Deposition Modeling

Abstract Sandwich panels are used in many industries for the advantageous properties of high stiffness, good strength to weight ratio, and impact resistance. This paper investigates properties of thin-walled cores manufactured through Fused Deposition Modeling (FDM); a process which, through a wider design space, could improve the functionality of sandwich panels. The bond strength between the layers of thin walls manufactured through FDM was evaluated through tensile testing. To measure the effect of modified manufacturing speeds, wall thicknesses were varied through the flow rate and nozzle speed. Honeycomb cores using FDM were produced with different toolpaths, and compared with an example of an industry standard Nomex honeycomb core. During tensile testing, thick-walled FDM components exhibited a more ductile failure with a lower yield point when compared to thinner specimens. The ultimate tensile stress remained constant across samples within each of the tested ABS and PLA polymers used. Honeycomb cores produced using FDM were found to have a higher compressive failure force than Nomex honeycomb, and a lower specific strength. The force–displacement curves of compressive failure show a ductile response for thick specimens, consistent with the previous result. These results, combined with the increased flexibility of additive manufacture technologies, could provide a method of manufacturing high strength cores with complex geometry.

Magnetostrictive Actuation of Fiber-Reinforced Polymer Composites

Despite substantial research into smart materials and structures technology, the integration of magnetostrictive materials into fiber-reinforced polymer laminated structures to provide capabilities such as actuation has been limited to date. In this work, magnetostrictive Terfenol-D is inserted into unidirectional glass and carbon fiber-reinforced polymer laminates. The strain developed in the laminates due to the magnetostriction of the Terfenol-D was observed and found to give a maximum of 0.11% normal to the fiber direction for a 3-ply UD carbon fiber laminate with the Terfenol-D recessed within a mid-ply cut-out. This demonstrates the actuation potential of Terfenol-D within a smart structure.