C Lira

A Gradient Cellular Core for Aeroengine Fan Blades Based on Auxetic Configurations

In this study, gradient cellular centresymmetric auxetic configurations are evaluated as potential cores for aeroengine fan blades, and optimized to reduce the dynamic response for the first three fundamental modes. Auxetic (negative Poisson’s ratio) re-entrant cellular beams are modeled, manufactured, and tested to assess their natural frequencies and mode shapes. Gradient versions of these beams with a varying internal cell angle are then designed to be incorporated as fillers in a baseline fan blade model. The optimized configurations of the gradient core lead to a substantial decrease of the mass of the fan blade, reduction of the dynamic modal displacements, and a lowering of the first three natural frequencies within the admissible frequency bandwidth.

Active articulation for future space applications inspired by the hydraulic system of spiders.

This paper presents and discusses a novel mechanism which was conceived taking inspiration from the micro-hydraulic system used by spiders to extend their legs. The mechanism has the potential to be used in future space applications, although the harsh space conditions, and in particular outgassing, should be carefully addressed in the design of a space-qualified model. The new system has one degree of freedom and is actuated by a pressurized fluidic system. The prototype, which has been designed, simulated, built and tested, is of compact size and presents a repeatable behaviour. The relation between pressure and rotation is approximately linear. The mechanism is suitable for a modular configuration in which several elastic joint modules are joined together. This modular configuration allows large rotations and does not increase the complexity of the actuation. A single module bends about 1.8 degrees when the pressure of the working fluid is 1.2 MPa.

A smart hydraulic joint for future implementation in robotic structures

A hydraulic flexible joint inspired by the actuation system of spiders is investigated in this paper. Its design and characteristics are discussed and a mathematical model is developed to describe its static behaviour. Results of experimental tests are presented to validate its performance. A comparison to other hydraulic actuation systems is performed. The use of the proposed hydraulic flexible joint in adaptive robotic structures is addressed and discussed.

Active inflatable auxetic honeycomb structural concept for morphing wingtips

This paper describes a new concept of an active honeycomb structure for morphing wingtip applications based on tubular inflatable systems and an auxetic cellular structure. A work-energy model to predict the output honeycomb displacement versus input pressure is developed together with a finite element formulation, and the results are compared with the data obtained from a small-scale example of an active honeycomb. An analysis of the hysteresis associated with multiple cyclic loading is also provided, and design considerations for a larger-scale wingtip demonstrator are made.

Mining Smartness from the Hydraulic System of Spiders: A Bioinspired Actuator for Advanced Applications

Most animals and insects use opposing muscles, called flexors and extensors, to articulate the joints of their limbs. However, some spiders do not have extensors in some of their joints and use, instead, a simple and efficient miniaturized hydraulic system to extend their limbs. An actuator inspired by the hydraulic system of spiders, which can be embedded on adaptive structures, is investigated in robot-like configurations in this paper. Its design and characteristics are discussed and the effects of the geometrical parameters on its performance are investigated.

Morphing nacelle inlet lip with pneumatic actuators and a flexible nano composite sandwich panel

We present a hybrid pneumatic/flexible sandwich structure with thermoplastic (TP) nanocomposite skins to enable the morphing of a nacelle inlet lip. The design consists of pneumatic inflatables as actuators and a flexible sandwich panel that morphs under variable pressure combinations to adapt different flight conditions and save fuel. The sandwich panel forms the outer layer of the nacelle inlet lip. It is lightweight, compliant and impact resistant with no discontinuities, and consists of graphene-doped thermoplastic polyurethane (G/TPU) skins that are supported by an aluminium Flex-core honeycomb in the middle, with near zero in-plane Poissons ratio behaviour. A test rig for a reduced-scale demonstrator was designed and built to test the prototype of morphing nacelle with custom-made pneumatic actuators. The output force and the deflections of the experimental demonstrator are verified with the internal pressures of the actuators varying from 0 to 0.41 MPa. The results show the feasibility and promise of the hybrid inflatable/nanocomposite sandwich panel for morphing nacelle airframes.