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Hou Y.,Donghua University | Hou Y.,University of Bristol | Tai Y.H.,University of Sheffield | Lira C.,University of Bristol | And 4 more authors.
Composites Part A: Applied Science and Manufacturing | Year: 2013

We describe the bending and failure behaviour of polymorphic honeycomb topologies consisting of gradient variations of the horizontal rib length and cell internal across the surface of the cellular structures. The novel cores were used to manufacture sandwich beams subjected to three-point bending tests. Full-scale nonlinear Finite Element models were also developed to simulate the flexural and failure behaviour of the sandwich structures. Good agreement was observed between the experimental and FE model results. And the validated numerical model was then used to perform a parametric analysis on the influence of the gradient core geometry over the mechanical performance of the structures. It was found that the aspect ratio and the extent of gradient (i.e. the horizontal rib length growth rate or the internal angle increment) have a significant influence on the flexural properties of the sandwich panels with angle gradient cores. © 2013 Elsevier Ltd. All rights reserved.


Sun J.,Harbin Institute of Technology | Sun J.,University of Bristol | Gao H.,Harbin Institute of Technology | Scarpa F.,University of Bristol | And 3 more authors.
Smart Materials and Structures | Year: 2014

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. © 2014 IOP Publishing Ltd.


Agnese F.,University of Bristol | Remillat C.,University of Bristol | Scarpa F.,University of Bristol | Payne C.,National Composites Center
Composite Structures | Year: 2015

The work describes a structural composite damper concept based on a chiral auxetic configuration. Chiral structures couple uniaxial and rotational deformations to provide a negative Poisson's ratio behaviour and high dissipation through shear strain energy, and this feature is exploited by up-scaling the deformation mechanism of the chiral cell to design a damper that dissipates energy in the edgewise/shear modes, like the ones occurring in wind turbine blades. The damper concept and its configuration are evaluated through a series of Finite Element parametric and probabilistic models. A small-scale demonstrator is manufactured and subjected to compressive cyclic loading at increasing maximum displacements. Good agreement between the numerical and experimental force-displacement and energy dissipated-displacement curves is observed, showing the feasibility of the chiral composite damper concept for vibration damping-related applications at low frequencies. © 2015 Elsevier Ltd.


Ozdemir N.G.,University of Bristol | Scarpa F.,University of Bristol | Craciun M.,University of Exeter | Remillat C.,University of Bristol | And 3 more authors.
Smart Materials and Structures | Year: 2015

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 Poisson's 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. © 2015 IOP Publishing Ltd.


Dell'Anno G.,National Composites Center | Treiber J.W.G.,Cranfield University | Partridge I.K.,University of Bristol
Robotics and Computer-Integrated Manufacturing | Year: 2016

The paper aims at providing practical guidelines for the manufacture of composite parts reinforced by tufting. The need for through-thickness reinforcement of high performance carbon fibre composite structures is reviewed and various options are presented. The tufting process is described in detail and relevant aspects of the technology are analysed such as: equipment configuration and setup, latest advances in tooling, thread selection, preform supporting systems and choice of ancillary materials. Effects of the process parameters on the preform fibre architecture and on the meso-structure of the reinforced component are discussed. Special emphasis is given to the different options available in terms of tuft insertion and loops management. Potential fields of application of the technology are investigated as well as the limitations of its applicability in relation to preform nature and geometry. Critical issues which may arise during the manufacturing process concerning thread insertion, loops formation, alteration to the fabric fibres layout or local volume fraction are identified. Copyright © 2015 Published by Elsevier Ltd. All rights reserved.

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