Extended projects: 2011 cohort
- Morphing high-temperature composite plates utilizing thermal gradients
- Optimising the energy potential of a magnetically-loaded composite flywheel
- Modelling of 3D woven fabrics for deformation and defect generation
- The development of novel chemistries for multifunctional materials
- Novel bio-inspired body armour developed through additive layer manufacturing
- A 2D equivalent single-layer formulation for the effect of transverse shear on laminated plates with curvilinear fibres
- Non-axisymmetric bending of thin annular plates due to circumferentially distributed moments
- Damage redirection and healing in skin-stiffener debonding specimens under fatigue conditions
- Electromagnetic interference shielding effectiveness of super- aligned MWNT films composites and randomly aligned MWNT composites
- Structural composites through 3D printing
- Novel porous wall vascular networks for repeated self-healing
- Uncertainty quantification in aeroelastic composite plate wings using lamination parameters
- The reinforcement effects of graphene oxide nanoplatelets on the mechanical and viscoelastic properties of natural rubber
Morphing high-temperature composite plates utilizing thermal gradients
Student: Eric Eckstein
Supervisor: Paul Weaver
Abstract Composite morphing structures often rely on thermal loading to achieve multistability, however new understanding of these structures may enable their use as temperature-driven actuators. An analytical model has been developed which predicts the shapes of multistable laminated plates subjected to thermal loads while accounting for thermal gradients and temperature-dependent material properties. Results from this research are key to the development of composite thermal actuators which can operate in high-temperature environments.
Optimising the energy potential of a magnetically-loaded composite flywheel
Student: Laura Edwards
Supervisors: Ian Bond, Phil Mellor, Crompton Technology Group (CTG)
Loading a composite flywheel with magnetic powder and placing this device within a stator creates a motor/generator system which can be used to store and release energy. However, the magnetic powder introduces areas of weakness into the composite structure which can reduce the maximum rotational speed of the flywheel and consequently also the kinetic energy. Here different analytical techniques, including finite element analysis, are used to evaluate the effect of volume and distribution of magnetic powder layers on the kinetic energy and electromotive force of a filament-wound composite flywheel.
Modelling of 3D woven fabrics for deformation and defect generation
Student: Bassam El Said
Supervisors: Stephen Hallett and Dmitry Ivanov
3D woven composites are a viable solution to the inherent low through thickness properties of conventional composites. However, one of the main challenges facing the wide use of 3D woven composites is the lack of numerical tools capable of modelling fabric behaviour. In practice, deformations and defects occurring in a woven perform during production are a result of tool/fabric interactions. Consequently, these deformations and defects are dependent on the tool geometry as well as the fabric architecture. Unit cell models fall short of capturing the tool geometry effects on the compacted fabric which can be of paramount importance for complex components. A mutli-scale modewlling approach combining high and low fidelity techniques is proposed in this project. This multi-scale approach involves building models on the meso and macro scales using different modelling approaches and degrees of fidelity. The multi-scale models are combined to offer a detailed hierarchal view of the 3D woven fabric architecture during and after compaction.
The development of novel chemistries for multifunctional materials
Student: Dan Everitt
Supervisors: Ian Bond, Duncan Wass and Richard Trask
The design of new catalysts is a crucial step toward the realisation of self-healing materials. This project currently involves the synthesis, solution phase testing, and integration into composite materials of new catalytic systems. Eventual aims include achieving mechanical activation of such catalysts, allowing for low temperature autonomous healing.
Novel bio-inspired body armour developed through additive layer manufacturing
Student: Ian Gent
Supervisors: Richard Trask and Stephen Hallett
Modern body armour relies on dense plates of brittle ceramics fracturing under ballistic impact loads to protect personnel from ballistic injuries. The problems with these systems are that they are heavy and that a large proportion of the energy from the projectile is transmitted to the body resulting in blunt force trauma injuries that can be fatal. This project aims to build on existing ACCIS research by experimentally testing a promising geometry of ceramic platelets in an arrangement similar to that observed in nacre, an impact resistant material found in nature. An additive layer manufacturing process is employed to simplify the production of the complex geometry used by the ceramic platelets. Impact tests are used to investigate the performance of the design and determine its suitability as a new design philosophy for impact resistant body armour.
A 2D equivalent single-layer formulation for the effect of transverse shear on laminated plates with curvilinear fibres
Student: Rainer Groh
Supervisor: Paul Weaver
In recent years advances in composite manufacturing technology have facilitated the production of laminates with variable angle tows (VAT), i.e. the fibre orientations change over the planform of the plate. Thus the plate rigidities (A, B, D) vary with x and y location providing designers with a broader design freedom for enhanced structural performance. To date the effect of transverse shear stresses on the flexural behaviour of laminated VAT plates remains unexplored. The aim of the current work is to derive an accurate model for practical panel thicknesses while minimising the added computational effort compared to thin-plate equations. For this reason, the Hellinger-Reissner mixed variational principle is used in conjunction with Lagrange multipliers and the calculus of variations to model the three-dimensional stresses arising in bending of laminated plates with curvilinear fibres using a reduced two-dimensional formulation. The novel formulation features multiple shear correction factors that are functions of the bending rigidity terms D, their first and second derivatives and the Timoshenko shear factor. The derived equations degenerate to Classical Laminate Analysis for very thin configurations but discrepancies as large as 43\% are observed for span-to-thickness ratios of 10:1. Finally, the specific VAT panels under investigation are affected more by transverse shear deformation than a corresponding homogeneous quasi-isotropic laminate.
Non-axisymmetric bending of thin annular plates due to circumferentially distributed moments
Student: Ettore Lamacchia
Supervisors: Paul Weaver, Alberto Pirrera and Isaac Chenchiah
This project studies the non-linear deformation of a thin annular plate subjected to circumferentially distributed bending moments. Linear analysis predicts that the annular disk deforms axisymmetrically into a spherical dome. However, non-linear analysis shows that the linear configuration may become unstable and snap into a non-axisymmetric cylindrical shell.
The principal axes of curvature in the deformed configuration do not have a preferred orientation. Hence this project represents a first attempt to describe a novel class of morphing structures with a potentially infinite number of identical equilibria.
Damage redirection and healing in skin-stiffener debonding specimens under fatigue conditions
Student: Rafael Luterbacher
Supervisors: Ian Bond and Richard Trask
One of the main failure modes in skin-stiffened structures is stringer debonding due to propagating damage. Therefore, during design, a "non growth" criteria for damage is envisaged. The aim of this project was to challenge this criteria and design and test a skin-stiffened element with the ability to redirect the damage into dedicated healing areas under fatigue loading. Selective interleaving was used in order to succesful redirect propagating delaminations into a vascular network through which a low viscosity epoxy resin could be injected in order to recover the mechanical performance of the element.
Electromagnetic interference shielding effectiveness of super-aligned MWNT films composites and randomly aligned MWNT composites
Student: Beene M'Membe
Supervisors: Sameer Rahatekar, Hua-Xin Peng, Geoffrey Hilton and Kristof Koziol (Cambridge)
The last few decades have seen a rapid development in electronics that often operate at high frequencies. This has created an increase in the electromagnetic interference (EMI) of electronics at high frequencies. Previously, metals were used for EMI shielding; however, they are heavy and have poor anti-corrosion properties. The project involves the analysis of the EMI shielding effectiveness (SE) and surface conductivity of glass fiber polymer composites coated with super-aligned multi-wall nanotubes (MWNT) films and commercially available MWNTs. The composites are manufactured using traditional vacuum bagging process for composite manufacturing. The EMI SE has been performed in the X-band range (8-12 GHz) using a horn antenna. The EMI SE and surface conductivity are shown to increase with increasing MWNT concentration. Effects of concentration and plasma functionalization of MWNT are studied.
Structural composites through 3D printing
Student: Robin Neville
Supervisors: Richard Trask and Bob Bradley (GKN Aerospace)
The aim of this work is to investigate the feasibility of producing fibrous composites through 3D Printing (3DP). Composites are widely used in the aerospace industry in structural components due to their excellent specific strength and stiffness, but are limited when it comes to producing very complex geometries. Conversely, 3DP is a process capable of producing virtually any geometry; as a result it is widely used for producing prototypes in near net-shape which do not require further machining. However, it is not used to produce structural components because most 3DP materials have poor mechanical properties, especially plastics. Fibrous composites produced through 3DP could potentially fill a gap in both fields, but this topic has received limited attention to date. This work focuses on creating short fibre-epoxy composites using 3DP, and characterising the effect of the fibres on mechanical properties. Future possibilities are also discussed, including the control of fibre orientation during deposition, and optimisation of 3DP tool paths.
Novel porous wall vascular networks for repeated self-healing
Student: Isabel Qamar
Supervisors: Richard Trask and Ian Bond
A key limitation in the vascular self-healing systems to date has been the inability to achieve repeated healing for an infinite number of cycles due to fracture of the fluid-carrying vessel, which ultimately restricts and then terminates the transportation of the healing agent throughout the structure. In order to overcome this limitation a novel concept employing a porous thermoplastic network integrated within a fibre-reinforced composite laminate has been utilised. This approach promotes adhesive failure between the network and the surrounding host matrix material, thus exposing a series of radial pores and permitting the secretion of the liquid healing agent into the damage crack plane. In this study, mechanical characterisation of the crack-vascule interaction through a fracture mechanics assessment of hollow thermoplastic tubes embedded within a fibre reinforced composite has been undertaken. The experimental characterisation of this system is on-going with self-healing trials imminent.
Uncertainty quantification in aeroelastic composite plate wings using lamination parameters
Student: Carl Scarth
SupervisorS: Jonathan Cooper and Gustavo Silva (EMBRAER)
Composite materials are subject uncertain properties due to variability which can be introduced during manufacture. Furthermore, the aeroelastic response of structures is difficult to predict accurately, and very sensitive to uncertainties in design parameters.
State of the art research in uncertainty seeks to develop efficient modelling techniques such as Polynomial Chaos Expansion, however, this technique suffers from 'the Curse of Dimensionality' whereby problems with a large number of uncertain variables become prohibitively large.
The project aims to account for variability in material properties through direct incorporation of uncertainties into an aeroelastic model, by modelling these properties as probability distributions rather than their ideal deterministic values. An efficient approach is developed for modelling composite structures subject to uncertainty in their ply orientations using Polynomial Chaos Expansion. Lamination parameters are used to represent the uncertainties, allowing ply orientation uncertainty to be modelled using no more than four parameters thus allowing any composite laminate to be modelled while keeping the model to a manageable size. The method is demonstrated for flutter of composite plate wings, using a Rayleigh-Ritz structural model interacting with modified strip theory aerodynamics.
The reinforcement effects of graphene oxide nanoplatelets on the mechanical and viscoelastic properties of natural rubber
Student: David Stanier
Supervisors: Jacopo Ciambella, Sameer Rahatekar and Avinash Patil
Pneumatic tyres are often manufactured into complex geometrical structures constituted by several different rubber compounds. Stiffer elastomers with low hysteresis are generally employed as principal components of the sidewall, shoulder and bead, and are required to sustain the vehicle load and display low wear rates. On the contrary, less stiff materials with low hysteresis at high temperature and high hysteresis at low temperature are used in the tyre tread. Having a low hysteresis at the working temperature drastically diminishes the tyre rolling resistance and, hence, the fuel consumption, while a high hysteresis at low temperature increase the vehicle drivability in wet conditions.
The aim of the proposed experimental investigation is to synthesise graphene nanoplatelets and disperse them in a natural or synthetic elastomer for improved mechanical properties and tailoring of viscoelastic properties of the graphene/elastomer composite. With their nanoscale dimensions, large aspect ratio, high stiffness, low density, excellent thermal stability and extremely high thermal conductivity, graphene oxide provides very high damping with minimal weight penalty. Indeed, a number of other properties are also expected to be enhanced (such as wear, fatigue and relaxation) and these present opportunities to more closely understand the reinforcing effects compared to carbon black.