4th ANNUAL CONFERENCE OF THE CDT IN ADVANCED COMPOSITES ... · CDT IN ADVANCED COMPOSITES FOR...

Tuesday 14th April 2015 University of Bristol, Queen’s Building, University Walk,

Bristol, BS8 1TR, UK

4th ANNUAL CONFERENCE OF THE

CDT IN ADVANCED COMPOSITES FOR INNOVATION AND SCIENCE

POSTER BOOKLET

Front cover photo credits: Michael Elkington (top left), Chris Bahn (top right), Dan Rowley (bottom left), Bristol City Council (bottom right)

Multifunctional Composites and Novel

Microstructures

www.bris.ac.uk/composites

Metal cation binding found in sandcastle worms has been used as the inspirationfor new synthetic hydrogels, these flat hydrogels have been transformed into3D shapes using “ionoprinting”1. This transformation is both reversible andreprogrammable via external stimuli and chelating agents, respectively. Thisapproach of hydrogel transformation uniquely allows for actuation ofhomogeneous hydrogels.

BIO-INSPIRED REVERSIBLE CROSSLINKING: USING CHELATING POLYMERS AND METAL ION BINDING, FOR USE AS SOFT

ACTUATION AND SELECTIVE GROWTH

Anna Baker, Duncan Wass & Richard Trask

Supported by

Ionoprinting

A technique used toselectively “print” metalions onto the surface of ahydrogel, allowing forcomplex 3D actuation andshape change.

Reference:1. Palleau, E.; Morales, D.;Dickey, M. D.; Velev, O. D. Naturecommunications 2013, 4, 2257.

How does it works?

The multiply charged metal ions, printed into thehydrogel, crosslink the polymer chains, which causeslocalised contraction and creates a hinge.

How is the actuation reversed?

The hydrogel globally shrinks in response to acidicpH and non-polar solvents (e.g. alcohol) causing thehinge to unfold, reversingthe actuation.

How are the printed metal cations removed?

The cations can be removed using a chelating agent(a chemical that binds more strongly to the cationthan the polymer), restoring the hydrogel to itsoriginal state. The hydrogel can be re-printed intoanother shape.


By replacing regions of the stiff core of a composite sandwich panel with compliant cellular materials, a shock absorbing functionality can be integrated into an otherwise rigid structure. Interactions between the panel skin and thermoplastic polyurethane (TPU) cellular core inclusions take place via controlled, elastic skin buckling. The response of the panel can be tailored via modifications to cell topology and strategic material placement.

DEVELOPMENT OF NOVEL COMPOSITE SANDWICH STRUCTURES WITH INTEGRATED

SHOCK ABSORBING FUNCTIONALITYSimon Bates*, Ian Farrow, Richard Trask

Supported by

*[email protected]

4 point bend force-displacement for sandwich panels with controlled skin buckling – finite element analysis

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Increased pre-buckle leads to smoother

transition

• Characterise behaviour of auxetic and conventional elastomeric cellular structures

• Optimise 3D printing of TPU for structural use• Utilise controlled buckling in panel design• Integrate a stiffness-tailored flexible core

Cellular Architecture

Ongoing work

Print optimisation and othotropy in 0° and 90° prints

Key variables:-Material flow-Layer height-Print direction

Figure 1: 0°thermoplastic polyurethane specimen printed for tensile testing

Figure 2: Stress-strain in tension, optimised variables, print direction 0°or 90°to the extension direction

Figure 4: 4 point bend force displacement data for controlled buckling of a sandwich composite using nonlinear finite element analysis (Rik’s method); 12mm core, D=0-2mm

Aims

Figure 3: 3D printer that has been adapted to print elastomers and examples of printed parts

• Characterisation of the energy absorption capability of TPU prints in compression

• Investigation into the effects of a stiffness gradient within the TPU structures

• Creation of practical inserts

Figure 5: Local compression of a 3D printed thermoplastic polyurethane hexagonal array


The addition of nanoscale features has been investigated as a method to improvethe macroscopic mechanical properties of short fibre-reinforced composites – inparticular ductility, a major challenge for structural composite materials. Zinc oxide(ZnO) nanorods have been grown on glass fibres under mild reaction conditions forincorporation into an additive layer manufacturing (ALM) printer to form 3Dcomposite materials that mimic hierarchical natural composites such as bone.

HIERARCHICAL COMPLEX FIBROUS ARCHITECTURES FOR ADDITIVE LAYER

MANUFACTURINGLaura Beckett, Wuge Briscoe, Richard Trask

Supported by

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ZnO Nanorod GrowthTwo steps –

1. Coat fibre in nanocrystalline ‘seed’ layer to ensure ordered, vertically aligned arrays of ZnO.

2. Grow rods radially from these nucleationsites at 93 oC in water.

The morphology of the rods can becontrolled in the following ways:

• Thickness of the seed layer,

• Growth time,

• Seed and growth solution concentration.

θ

Water (polar)

Diiodomethane(non-polar)

Clean Slide

Seed Only

Nanorod Growth

Scanning electron microscope images of ZnO coverage on 31 μmdiameter glass fibres. Rod diameter ≈ 250 nm.

Relationship between average rod diameter and growth time (left) and seed thickness (right).

• No decrease in tensile strength after ZnO nanorod growth compared with base fibre.

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Surface Properties• Measured angle (θ) made by liquid

droplets on a glass slide to determine effect of rods on infiltration.

• Demonstrated that ZnO rods lead to increased surface wetting compared to bare glass or seed layer only.

Future Work• Incorporation of fibres into composite

material using suitable polymer.

• Investigate effect of nanorods on failure mechanism and interfacial properties.

Fibre Tensile Strength


Inductively coupled sensors can be embedded within composite materials, andwireless ultrasonic measurements made using an external probe. This sensingnetwork is primarily designed to detect impact damage, however the work in thisproject focuses on integration of the sensors within composite structures, andmonitoring the curing process of the surrounding material.

EMBEDDED INDUCTIVELY COUPLED SENSORS FOR STRUCTURAL MONITORING

Jamie Chilles*, Anthony Croxford, Ian Bond

Embedded sensors are interrogated by an external probe, allowing wireless ultrasonic measurements to be made from fixed locations.

Supported by

Sensor integration

Cure monitoring

Conclusions

Figure 4: Amplitude and velocity of signal recorded throughout cure.

Sensors can be embedded withoutsignificantly reducing the mechanicalperformance of composite structures.

Sensors successfully monitor the cure ofthe surrounding composite.

*[email protected]

Inductive coupling

The sensors can be used to monitor thecuring process of the surroundingcomposite material.

Encapsulating layer identified byinterlaminar shear strength testing.

Figure 1: Schematic illustrating sensor operation and the inductive coupling.

Figure 3: Embedding strategies applied to integrate sensors.

Sensors embedded into four-point bend specimens; no reduction in flexural strength observed.

Figure 2: Inductively coupled sensor encapsulated within polyimide.

www.bris.ac.uk/compositeswww.bris.ac.uk/composites

Progress:

Future work:

Aim: To produce a nanocomposite wound dressing material which elutes antiseptic at a sustained, and controlled, rate.

ANTIMICROBIAL NANOCOMPOSITE WOUND DRESSINGS

Find out more:

a) b)

Background:

Figure 2. Chlorhexidine hexametaphosphate nanoparticles (nps).

Antiseptic deliveryAntiseptic nanoparticles (Fig 2) activelyleach the active agent (chlorhexidine) intoan aqueous environment.

Chronic woundsChronic wounds are vulnerable to infectionoffering prolonged access for microbes.

A continuous supply of antiseptic to thewound bed would reduce infection rates.

Figure 1. Diabetic foot ulcers have a high risk of infection.

Material developmentNanoparticles have been encased within apolysaccharide matrix and processed intofilms and fibres (Fig. 3).

Figure 3. a) TEM of a nanocomposite film shows the intact nanoparticles. b) SEM of a nanocomposite fibre (ø ~ 50 µm).

[email protected]

Project scope• in vivo experiments (Fig. 6).

• Electrospinning to produce a non-wovenfibrous mat – similar to commercialwound care materials.

Peter F. Duckworth, Sarah E. Maddocks, Andrew M. Collins, Sameer S. Rahatekar* & Michele E. Barbour*

*project co-supervisors

Antimicrobial studiesAlginate nanocomposite films show a dose-dependent antiseptic elution (Fig. 4)...

...and hence dose-dependent in vitroantimicrobial action against MRSA (Fig. 5)

Figure 5. Antimicrobial action of alginate films against MRSA.Clear zones are locations of inhibited bacterial growth. From L-R: control, 3 wt% nps, 6 wt% nps, commercial silver np dressing.

Figure 4. Chlorhexidine elution from alginate nanocomposite films.

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Figure 6. A guinea pig.

Supported by


The effect of incorporating anisotropic permeability into a fibre reinforced polymercomposite containment sleeve was investigated. Finite element analysis identifiedmaximum air-gap flux density for a combination of high radial and lowcircumferential sleeve permeability. A 50% increase in the fundamental componentof air-gap flux density can be achieved with this anisotropic arrangement.

A COMPOSITE CONTAINMENT SLEEVE WITH ANISOTROPIC PERMEABILITY FOR HIGH-SPEED

PERMANENT MAGNET MACHINESLaura Edwards, Jason Yon, Ian Bond, Phil Mellor

IntroductionHigh-speed Surface-Mounted Permanent Magnet machines show high power-to-weight ratios, so are increasingly employed in mass-critical applications.

Supported by

air-gap flux density (F1) for different sleeve permeability values:

• Maximum air-gap flux density with high radial and low circumferential permeability

• Possible 50% improvement in F1 with anisotropic sleeve

Maximum for isotropic sleeve

Further WorkWith the potential to achieve significantimprovements in air-gap flux densityidentified, further investigation will cover:

• The feasibility of achieving anisotropicpermeability via Z-pinning

• Effect of anisotropic sleeve on torque ripple

ExperimentalFEA determination of

fundamental component of

• Larger ↑ detrimental, as acts to “short-circuit” rotor flux

• Small ↑ in sleeve permeability improves magnetic loading

• Containment sleeve required to retain magnetic material at high speeds

• Sleeve ↑ effective air-gap, reducing magnetic loading of the machine

ConceptApply anisotropic permeability to sleeve to increase machine magnetic loading, via:

• Increasing radial permeability to increase air-gap flux density

• Lowering circumferential permeability to minimise “short-circuit” effect

www.bris.ac.uk/compositesSupported by

Inclusion of a catalytic curing agent, Sc(OTf)3, in fibre reinforced polymercomposites during hand layup yields a material with an embedded self-repairfunction. The inclusion of this agent has a minimal impact on material properties,and has been shown to achieve full recovery of pristine material performance.

EMBEDDED CATALYSTS FOR IN-SITU REPAIR OF FIBRE-REINFORCED POLYMERS

Daniel Everitt, Duncan Wass, Ian Bond

Functionalised FRP

• Embedded healing functionality

• Not detrimental to pristine material properties

• Able to achieve full recovery Embedded Catalyst

• Catalytic healing agent remains active following cure of the host material.

- Higher temperature systems also possible.

• Localised catalyst leads to localised healing.

• Full strength recovery is possible after rebonding as little as 20% of the fracture surface.

- Due to high toughness of the healing resin.

Following crack propagation and exposure of the catalyst epoxy monomer is delivered.

Sc(OTf)3 incorporated into DCB specimens during

hand layup.

Full recovery of pristine material properties is possible.

• Future integration of embedded catalytic healing:

- Ply drops.

- Butt joints.

Resin pocket at butt joint functionalised

for healing with embedded Sc(OTf)3


We aim to develop a new biomimetic polychromatic smart material, focussed at the single unitcell level. This will allow for the generation of a low-cost low-weight highly efficient soft structurefor integration of colour-changing potential within a military setting, through production ofpolydimethylsiloxane films containing photonic crystals made from polystyrene spheres.

POLYCHROMATIC COMPOSITE FILMS FOR ADAPTIVE CAMOUFLAGE

Ian Gent, Richard Trask, Nicholas Roberts and Annela Seddon

Inspiration There are a number of examples in nature ofstructural colour and changing of colouration toaid survivala) Photonic crystal made of spheres – Weevil [1]b) Photonic crystal made of inverse spheres – Emerald

Swallowtail butterfly [2]c) Layers and channels that can be swollen to change colour –

Golden Tortoise beetle (gold to red colour transition) [3]

Supported by

Specimen ManufacturePolydimethylsiloxane (PDMS) with self-assembled microstructure comprised of 240 nmpolystyrene (PS) microspheres

a) b)

Spectral Shift Under Tensile LoadingShift in wavelength from 611 nm (red) to 569nm (green) when sample stretched by 5 mm @10 mm/min

Future InvestigationsSpecimen stiffness tailoring to ensure that thearea undergoing the greatest mechanical straincontains the photonic crystal

Multi axial tensile testing of manufacturedmorphologies to quantify colour change

Inclusion of liquid crystal phase into inversecrystal to allow for dual mechanisms of colourchange

c)

[1] J. Galusha et al. J. Mater. Chem. (2010) 20: 1277–1284 [2] P. Vukusic et al. Nature (2000) 404: 457 [3] J. Vigneron et al. Phys Rev E (2007) 76: 031907

References

1. 1st PDMS pour

4. Complete sample (Gauge length: 33 mm)

2. PS spheres deposited

3. 2nd PDMS pour

Areas of PDMS and photonic crystalAreas of PDMS with local reinforcement

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Experimental Set upSpecimen were tested under the followingconditions

Fibre optic probe to spectrometer

Fibre optic probe fromhalogen light source

SEM image of the embedded microstructure

Bi-axial testing rig. A change of internalpressure will be utilised to deform themembrane. Strain field will be recordedusing digital image correlation andspectroscopy measurements taken.

Specimen configuration with reinforcement

Strain field ofspecimens withreinforcement,recorded usingdigital imagecorrelation

• Loaded in tension at a rate of10mm/min

• Illuminated by a halogen lightsource at 45°

• Light reflected collected normalto the surface and analysed over300-900 nm.

Completed specimens

Deformed


The in-plane mechanical response of a Dyneema® based composite has beeninvestigated at varying strain rates and hot-press consolidation pressures. Shearand tensile strength both increased at higher strain rate, whilst consolidationpressure caused an increase in maximum shear strength. Due to the low shearstiffness of the material, strain variation was observed in the tensile gauge regionand is thought to be the cause of large variation in open literature stiffness values.

COMPOSITE PROTECTIONMark K. Hazzard, Paul T. Curtis, Lorenzo Iannucci, Stephen Hallett,

Richard Trask.

Supported by

Manufacturing

Future Work

±45 Shear Testing0/90 Tensile Testing

θ = 65° after spring-back

Gel spun ultra-high molecular weightpolyethylene fibres produced by DSM werecross-plied into a 0/90/0/90 configuration.Plies were then stacked and hot-pressed at120°C at 10 MPa, 20 MPa, and 30 MPa.Microstructural investigation revealed plywaviness and fibre indentation. Specimens arefinally water-jet cut for testing.

0/90/0/90 Cross Ply Hot Pressed Cross Section Hot Press Indentation

• Custom specimens to avoid slip and delamination at grips.

• Testing dominated by intra-laminar slip, causing strainvariation in the gauge region, confirmed by FEA.

• Classical shear failure over a large length of the gaugeregion due to large amounts of delamination.

• Causes a highly non-linear shear response, largely causedby fibre re-alignment to loading axis.

Classical Impact Behaviour

Model with Boundary Capture Modes of FailureTensile and shear properties will be input into aballistic model in LS-DYNA and compared with testresults. A homogenised model with elastic-plasticcriteria and element deletion will be used andcompared with results. Taking inspiration fromnature, novel hierarchical fibre architectures willbe trialled and investigated to improve impactperformance.

20 MPa

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Intra-laminar shear and fibre re-alignment

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Ultrasonic manipulation was used to arrange glass microfibres within a UV curableresin tank. A 3-axis controller was then used with a UV light source to selectivelycure regions of the resin to produce 3-D printed parts with oriented short fibrereinforcement.

Thomas Llewellyn-Jones, Richard Trask, Bruce Drinkwater

Aims• To manipulate glass microfibres within a viscous UV curable resin system.

• To selectively cure regions of the resin.

• To remove an intact part from the resin tank after curing.

Supported by

3-D PRINTING WITH ACOUSTICALLY ORIENTED SHORT FIBRE REINFORCEMENT

Results• Glass microfibres align along acoustic

pressure nodal planes.

• Selective resin curing achieved.

3-D Printing Process• Ultrasonic manipulation rig attached to

FDM style printer bed.

• Printer extruder head replaced with focused UV light source.

Alignment Process

• Fibres dispersed in UV curing resin.

• 2MHz counter-propagating wavefrontsproduce standing wave field.

• Glass microfibres align along the acoustic pressure nodes.

• Transducers switched off during print stage.

Conclusions• Acoustic manipulation combined with

SLA style 3-D printer can produce parts with oriented microfibres, with potential for layerwise orientation change.

Left: Glass microfibres aligned within 3-D printed part. Right: Example of a 3-D printed part containing ultrasonically aligned microfibres.

• Acoustic manipulation combined with SLA style 3-D printer can produce parts with oriented microfibres.

Focused UV light source attached to 3-axis controller.


Vascules placed in the 02/902 interface in cross ply laminates have been shown tohave no knockdown effects on the mechanical performance and damage patternunder tensile static and fatigue loading. Intra-laminar damage has beensuccessfully repaired and the potential of using this vascule–damage modecombination for repeated repair scenarios is highlighted.

IN-SITU REPAIR OF INTRA-LAMINAR DAMAGERafael Luterbacher, Richard S.Trask, Ian P.Bond

Supported byFuture work

Transfer technique from cross-plylaminates to more complex structures,such as skin-stiffener debond specimen

• Intra-laminar damage is one of theearliest damage modes within compositesand act as initiation point fordelaminations

• Autonomous repair of transverse damageis crucial for structural applications

Transverse damage in skin-stiffener debond specimen

Transverse damage in cross-ply specimen

Motivation

Influence of vascules on mechanical properties

• Central vascule in 02/902 hasno significant influence onmechanical tensile static andfatigue properties

• Similar crack density asfunction of strain underinterrupted tensile loadinghas been observed

• Low viscosity healing agent isintroduced into vascule via asyringe pump

• Stiffness successfully recovered

• Vascule is oriented perpendicularto damage plane. Potential ofremoving healing agent fromvascule assuring continuity aftercuring

Recovery of static mechanical properties


The research was carried out to characterise the deployment of folded paper architectures inwater with the aim of ultimately developing programmable materials. Concentration gradientand capillary driven deployment in different kinds of paper folds were investigated andcharacterised. The results show the clear role of hydration and interaction of hydrogen bondswithin fibrous architecture to drive the deployment of folded regions. Some concepts ofreversible deployment involving the functionalisation of cellulose fibres are on going

PROGRAMMABLE DEPLOYMENT OF ORIGAMI ARCHITECTURES

Manu Mulakkal, Richard Trask, Annela Seddon, George Whittel andIan Manners

Reversible Deployment Investigation

Surface modification with Thermo -

responsive polymersChange in

temperature Hydrophilic to hydrophobic

transition

Driving out water and prevent further

ingress

References1. Antoni P, Carlmark A, Lindqvist J, Nystro D, Emma O, Johansson M, et al. Intelligent

Dual-Responsive Cellulose Surfaces via Surface-Initiated ATRP 2008:2139–45.2. Gao G, Dallmeyer JI, Kadla JF. Synthesis of Lignin Nano fibers with Ionic-Responsive

Shells: Water- Expandable Lignin-Based Nano fibrous Mats 2012.

Actuation time for single folds (s)Samples Below LCST Above LCSTNeat (control) 5 <1Grafted 23 >120*

*Holds deployment at mid way point

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Printer paper Sekishu 30 Lokta 30 Lokta 60 Grease-proof

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Triton SDS SDS ST Triton ST

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Actuation time Surface tension

Paper fibres before and after polymer grafting

Hydrophilicabove lower critical solution temperature (LCST)

Hydrophobic32 0C

Affiliations: ACCIS, NSQI and School of Chemistry

Origami Folding and Deployment Steps

Supported by

a) Shape profile [dimensions in mm]b) Manually folded shape c) After deployment in water d) Partial recovery upon drying

Design, Analysis and Failure


Quasi-static Finite Element models of quasi-isotropic laminates have beenevaluated for free-edge delamination failure. A comparison between laminateswith blocked plies have been made, 45𝑚𝑚𝑚𝑚, 90𝑚𝑚𝑚𝑚,−45𝑚𝑚𝑚𝑚, 0𝑚𝑚𝑚𝑚 𝑠𝑠𝑠𝑠 where 𝑚𝑚𝑚𝑚 ∈ ℕ ∶ 1,2,4,8 . Anadditional switched-ply case is also considered, where a single 90° ply isrepositioned to directly under the first 45° ply for the 𝑚𝑚𝑚𝑚 = 4 laminate,45,90, 453, 903,−454, 04 𝑠𝑠𝑠𝑠. The assumption being that this would reduce the overallthickness of the outer ply block, thus reducing the potential Energy Release Rate(ERR) and consequently delay the onset and propagation of delamination. Twoalternate failure mechanisms are observed and both are shown to agree with thetrends of experimental data. Comparisons to a closed form solution found inliterature [1,2] have been made.

A COMPARATIVE STUDY OF ANALYTICAL AND COHESIVE-BASED LAMINATE FAILURE MECHANISMS

DOMINATED BY FREE-EDGE DELAMINATIONBradley Cox, Michael Wisnom, Stephen Hallett

Supported by

[1] T. K. O’Brien, Characterization of delamination onset and growth in a composite laminate, Damage in Composite Materials, ASTM STP (1982)[2] S. A. Salpekar, T. K. O’Brien, Combined Effect of Matrix Cracking and Stress-Free Edge on Delamination, Tech. rep., NASA, Langley Research Centre, Virginia, (1990)

45° mc 45/90 90° mc 90/-45 -45° mc -45/0 Maxm=1 883 828 882 873 867 867 884m=2 579 592 605 610 592 585 614m=4 362 390 430 431 411 407 431m=8 n/a 240 289 290 302 301 312

mc: Matric Crack

Table 1: FE Results for failure stress at interface of blocked plies, MPa:

45/90 90/-45 -45/0m=1 n\a n\a n\am=2 418 (13.8) n\a n\am=4 316 (11.4) n\a 458 (5.8)m=8 222 (10.3) n\a 321 (2.9)

45/90 90/-45 -45/0897 877 1266700634 620 895670448 439 633330317 310 447830

Table 2: Experimental Testing, MPa: Table 3: O’Brien Closed Form, MPa:

842

911

929

660

458

321

1077

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Dispersed, n=1

Dispersed, n=2

Dispersed, n=4

Blocked, m=2

Blocked, m=4

Blocked, m=8

Classical Laminate Theory

Tensile Strength (MPa)

Aim:• To better understand the mechanisms involved in

delamination and how can we learn from this improved understanding.

Research Areas:• Quasi-static Finite Element Analysis models.• Closed form solutions used to predict failure stress

due to delamination presented by T. K. O’Brien [1, 2].• Comparison to experimental data for blocked plies and

switched ply cases.

Motivation:• Figure 1 illustrates experimental data of various

laminates, all of which provide the same Classical Laminate Theory (CLT) Failure stress.

• Lower nominal failure stresses are observed for thicker ply-blocks.

• Unexpectedly, thinner dispersed plies do no achieve CLT failure strengths.

Figure 1: Empirical Failure Stresses compared to CLT prediction

Future Work:• Further development closed form solutions developed by

O’Brien [1,2] to include orthotropic stiffness variables. • Further development of FE models with respect to the

switched ply case is required.

Findings:• FE predicts accurately the failure mechanism of

blocked plies. Delamination occurring from outer-most 45° ply-block and propagates down through the laminate cracks.

• O’Brien’s closed form solutions also predict closely the failure stresses of blocked plies.

• O’Brien fails to differentiate between blocked plies and switched plies accurately.

• FE predicts an alternative failure mechanism for the switched ply case laminate. Delamination occurring within the laminate at the 903,−454 interface, then propagating up and down through the laminate.

• Catastrophic failure always occurs at the −454, 04interface.


Improving aircraft efficiency to reduce fuel consumption is of crucial importancefor aircraft designers. Controlling the deformed shape of the wing can produce fuelsavings. This is done by controlling the aeroelastic properties and is known asaeroelastic tailoring. This research proved that challenging established wingdesign rules inherited from metallic structure can offer significant control ofaeroelastic properties.

AEROELASTIC TAILORING USING STRUCTURAL MEMBERS SHAPE & ARRANGEMENTGuillaume Francois, Jonathan Cooper, Paul Weaver

Current Wing Design

Supported by

Increased Design Freedom

Design Practice

• Limited Consideration for Aeroelastic performance

Structural Arrangement: Rib/Spar Orientation

Structural Member Shape: Curvilinear Ribs, Spars & Stringers

A320B737

Example: Structural ArrangementsImpact assessed on un-tapered, un-swept wings using:

• High Fidelity Finite Element (Modelling)

• 3D Printed Wing and DIC measurement method (Experiment) (Work in Progress)

Example of Results: Static Load at Tip

RibSpar

Limited Design Freedom

• Straight Ribs, Spars and Stringers

• Limited Rib/Spar Arrangement

[1] M. C. Y Niu, Airframe Structural Design, 1988.

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Variable angle tow composites use advanced automated manufacturing processesto steer fibres in curvilinear paths. The stiffness and strength of a laminate cantherefore be tailored within a layer by steering and through-thickness bycombining multiple layers into a laminate. Research at the University of Bristol hasdeveloped a promising new manufacturing technique known as Continuous TowShearing (CTS) which reduces manufacturing defects compared to standard AFPmachines. One characteristic of the CTS process is that the thickness of a tow iscoupled to the amount of steering. Thus, CTS panels provide increased freedom totailor the structural performance of flat and curved panels. This work shows thatmass of a typical aircraft wing panel can be reduced by up to 30% compared to aquasi-isotropic baseline design.

MASS OPTIMISATION OF VARIABLE ANGLE TOW,VARIABLE THICKNESS AIRCRAFT PANELS

Rainer Groh and Paul Weaver

Compression buckling of aircraft panels is improved by tow steering and thickness variation

• Fibres are steered to align with the loading direction at the edges

• Fibre variation is chosen to increase thickness towards edges

Thus, compression loads are re-directed to supported edges and buckling loads are increased.

Supported by

Aircraft Wing Panel

Initial Postbuckling BehaviourCTS Load Re-distribution for

Buckling Improvements

• Tow steering can also improve the initial postbuckling stiffness of aircraft panels

• However, the curved profile of the thickness variation may lead to shell-like, unstable postbuckling behaviour.

Tow-steered designs

Straight-fibre design

Optimised CTS designs reduce mass by 30% compared to straight fibre design

Further mass savingspossible if non-linear postbuckling regime is exploited


An adaptive, aeroelastically-tailored blade is designed to twist upon bending tofollow the theoretically optimum shape for improved energy yield and loadalleviation. The desired shape varies with wind speed. The 5MW NREL (NationalRenewable Energy Laboratory) turbine was used as a platform for development.The optimised twist response of its 61.5m blade is achieved by tailoring materialand structural bend-twist coupling. Matlab and Bladed are used for the analysis.

ADVANCED AEROELASTIC TAILORING OF COMPOSITE WIND TURBINE BLADES

M. Othman, D. Langston, G. McCann, P. Weaver, A. Pirrera

Supported by

2) Structural designMaterial/layup (Carbon/epoxy FRP)

•Baseline [±45n, 0n, 90n]s

•Adaptive blade [±45n, ϑn, 90n]s

Wind turbine design: conventional internal layout with curved planform.

4) Conclusion• Small % loss in AEP (Adaptive WT

arrangement with pitch control).• Reduction in loads due to 50 years gust.• Potential for pitch-less control.

1) Aerodynamic analysisChange of optimum twist distributions along the blade span for varying wind speeds.

Total twist = pre-twist + pitch angle + elastically-induced twist

Representative planform and fibre orientation

Rated

Increasing radial position

3) Results(a) Annual Energy Production (AEP)

*The ideal blade is defined as the blade that deforms to match the optimum twist distributions exactly (WT arrangement without pitch control).

(b) Load alleviation

• Reduction in flapwise and edgewise loads.• Reduction in root bending moments.


Interface analysis of a modular GFRP footbridge concept inspired by prestressedconcrete construction is presented. Structural analysis of the bridge isdemonstrated. Material properties of trial manufacturing elements arecharacterised. Finite element analysis is performed to quantify the interfacialresponse under load. Layup and misalignment variation effects are investigated.The results have shown that wrapping the fibres around the interface helps indissipation of stress concentrations. The presence of resin not only does notprevent stress concentrations, but can create them.

EFFECTS OF LAYUP AND MISALIGNMENT IN A POST-TENSIONED GLASS FIBRE-REINFORCED

POLYMER MODULAR BRIDGEJakub Rycerz, Alberto Pirrera, Natalie Price

Objective:• To predict how the module interfaces

would behave under service loads

Methods:• Structural analysis

• Standard material testing

• Finite element analysis

Supported by

Fig. 1: Construction sequence

Fig. 2: Module simplification

Sections were simplified and analysedto provide loading input for the finiteelement model. Material testing wasundertaken in order to assess realmaterial properties for the model.

Two-dimensional model was createdas a simplification and analysed withintroduction of various parameters:• Resin pockets

• Face misalignment

• Wrapping fibres around interface

Findings:• Features create stress concentrations

that can lead to delamination

• Surface resin films do not relieve stress, but magnify it

• Wrapping the fibres around interface decreases delamination potential

Future work:• Investigate long-term effects

Fig. 3: Two-dimensional simplification and stress results for one of the cases


Optimisation Results• Proximity to discontinuity leads to significant variability in deterministic optimal design

• Reliability improved by 39% through moving coupling parameters away from discontinuity

Uncertainty Quantification Results• Mode-switch results in discontinuous response• [45, -453, 02, 902]S example laminate

Robust design seeks to minimise the sensitivity of optimal designs to uncertainty.An efficient robust optimisation technique is presented for the aeroelastic stabilityof an idealised composite wing. Manufacturing process variability is accounted foras ply orientation uncertainty. Results are compared to deterministic optima whichmaximise the critical instability speed without accounting for ply orientation error.

ROBUST AEROELASTIC DESIGN OF COMPOSITE PLATE WINGS

Carl Scarth, Pia Sartor, Jonathan Cooper, Paul Weaver

Supported by

Approach Overview• Idealise wing as composite plate• Solve equation of motion using Rayleigh Ritz• Gaussian Process (Kriging) surrogate model

enables efficient uncertainty quantification• Genetic algorithm to search complex design space • Minimise probability that instability occurs at

design airspeeds

( ) 0][][][][ 2 =+++ qECVqBVqA ρρ Mass Aerodynamic Stiffness

Aerodynamic Damping Stiffness

Flutter 1 Flutter 2

Divergence

Instability speed trends with varying bend-twist coupling parameters

Input PDF crosses mode boundary

Comparison of emulated PDFs using differing quantities of training data with simulated model PDF

Objective LayupReliabilitywith Vdes =

145 m/s 150 m/s

1) [-452 452 02 ∓45]S 72% 62%

2) [-453 452 -452 45]S 99.8% 92.1%

3) [-45 ±45 0 -452 0 -45]S 97.8% 94.6%

2) Vdes = 145m/s

3) Vdes = 150m/s Flutter 1Flutter 2

1) Deterministic Optimum

Reliability of optimal designs with differing objectives

Comparison of instability speed PDFs for optimal deterministic and robust designs with different objectives


MICRO-SCALE MODELLING OF COMPOSITE FIBRE VOLUME FRACTION EFFECTS ON

TRANSVERSE MECHANICAL PROPERTIES

Macro-scale modelling of fibre-reinforced composites requires understanding oftheir micro-mechanical behaviour including complex failure modes. The localvolume fraction (Vf) affects microscopic properties and though composites aredesigned assuming average Vf, in reality, local Vf may vary significantly, withareas as high as 80% Vf. The difficulty in manufacturing and testing suchsamples has lead to little modelling work in this area. In the 1980s Chamis [1]

formulated equations for properties based empirically on known response at lowerVfs but these remain unverified.Aiming to understand and model how high Vf regions affect transverse mechanicalproperties, this investigation looked to create numerical models fromrepresentative volume elements (RVE). Models match the behaviour observed inexperimental analyses, and further work in this area will contribute to theaccuracy of composite modelling.

Emily Withers, Stephen Hallett, Jonathan Belnoue

Supported by

Findings and future workMethod created for generating models including: • Representative fibre distributions• Cohesive elements• Periodic boundary conditions

High Vf geometry caused difficulty in meshingA realistic crack path was shown under loadFuture work could include:• Parametric study including energy release rates in

cohesive material model• Development of algorithm to achieve higher Vf• Include resin cracking capability in material model

References[1] Chamis CC, NASA Tech. Memo. 83696., 1984

[2] Hobbiebrunken T, et al., Comp. A, 2006

MethodMATLAB algorithm generates fibre distribution for the RVE which is:• Random• Specified Vf• Periodic at RVE boundaries

Model creation and meshing performed in PATRANMaterial models applied and cohesive elements added in LS-DYNAPeriodic boundary conditions applied (mimics effect of surrounding material)Analysis run on varying RVE dimensions and Vfs

AimsModel regions of high local Vf

Incorporate cohesive elements to model mixed-mode interfacial behaviourAnalyse models with respect to the transverse mechanical properties

Fig. 1: Initial failure in composite laminate [2]

Fig 2: Deformation and von Mises stress of loaded 72.5%Vf

Crack path

Intelligent Structures


-20 0 20 40 60 80 100 120 140-0.5

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7z

Beam A Present modelBeam A FEMBeam B Present modelBeam C Present model

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w (m

m)

The bending behaviour of sandwich beams using an axially graded honeycombcore is investigated using a layer-wise sandwich beam model. Various beamgeometries and different boundary conditions are studied with geometricallynonlinear effects considered. Results show that stiffness variation in the coresignificantly affects the displacement, strain and stress field of the sandwichbeams.

STATIC RESPONSE OF SANDWICH BEAMS USING A VARIABLE STIFFNESS CORE

Qing Ai, Paul Weaver

Supported by

Background• Efficient and accurate design tools are

required for laminated sandwich structures,which have found wide ranging applicationsin the aerospace, marine and automobileindustries

• Functionally graded cores have been used insandwich beams due to their structuralpotential and functional performance

Reference[1] Rao D.K. Static response of stiff-cored unsymmetric sandwich beams. Journalof Manufacturing Science and Engineering 1976;98:391-396.

Methodology• Polynomial variations of the core’s in-plane

Young’s modulus are considered for sandwichbeams of fixed ends (C-C) and fixed-freeends (C-F)

• Rao’s layer-wise sandwich beam [1] model isextended to account for beam geometrytaper and core stiffness variation

• The minimum potential energy principle,combined with the Ritz method, is used toobtain the governing formulations andapproximate solutions

Results• The current model provides accurate

prediction of beam deflection andstresses compared with FEM results

• Under certain core stiffness variation, thestatic response of sandwich beams hasbeen significantly affected (Fig. 1 andFig.2) with particular interest in beamdeflection profiles

Figure.1 (a) ‘ZZ’ phenomenon in axial stress distributionalong beam thickness; (b) the transverse displacement ofC-C type uniform sandwich beams using core of certain axialstiffness variation

(a)

(b)

Figure.2 (a) ‘ZZ’ phenomenon in axial stress distribution alongbeam thickness; (b) the transverse displacement of C-F typetapered sandwich beams using core of certain axial stiffnessvariation

Future work

(a) (b)

With the current model,optimisation of a morphingtrailing edge usingbending stiffness tailoredhoneycomb core can befacilitated.

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Beam D- LMBeam D- FEMBeam E- LMBeam F-LM

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 185

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(MPa

)


INTELLIGENT SELF-ACTUATING COMPOSITE STRUCTURES

Michael PM Dicker, Ian P Bond, Paul M Weaver, Jonathan M Rossiter and Charl FJ Faul

Supported by

NN OHCH3

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6

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8

9

10

11

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Time (minutes)

light on

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NNH3C

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Angle of Incident Light

Pos = 0

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This project is concerned with the development of self-actuating structures fromchemically activated hydrogel composites. The project goes on to examine themanipulation of such structures with sensing and control inputs generated bychemical reactions. The aim of doing so is to create new classes of sentientstructures which can intelligently change their orientation or configuration inresponse to their environment. Such devices would mimic the distributed sensingand solid-state actuation so often seen in Nature, resulting in robust, highlyreliable multifunctional structures. In the future such devices could find applicationin solar power generation, efficient aerospace structures and soft robotics.

d.

RCOOH RCOO- + H+pH > 6.9

pH < 6.9


Thermal stresses within fiber-metal laminates are exploited to createtemperature-driven actuators with unique properties. Unlike bimetallic strips,composite actuators can be designed to act at specific triggering temperatures,and can exhibit snap‐through behavior and multistability. Ongoing researchfocuses on demonstrating the aforementioned concepts using ceramic matrixcomposites. Potential applications include variable geometry gas turbinecomponents and spacecraft thermal control.

THERMALLY-DRIVEN SNAP-THROUGH AND MULTISTABILITY OF LAMINATED FIBER-METAL SHELLS

Eric Eckstein, Paul Weaver

Supported byImpact

ModellingRayleigh-Ritz multistability model1 with vonKàrmàn plate kinematics, accounting for:

• Initial curvature.

• Through-thickness thermal gradients.

• Temperature-dependent material properties.

• Non-thermoelastic strains.

Core and bypass chevron deployment

Autonomous aero control in extreme environments such

as the gas turbine hot section

1. E. Eckstein et al. Thermally-driven snap-through and multistability using laminated fibre-metal shells. 16th European Conference on Composite Materials, June 2014

Passive thermal control louvers

Mechanics and ResultsAn asymmetrically laminated UD-CFRP/Aluminum laminate is cured at 180°C on a cylindrical tool with curvature oriented perpendicular to the fiber direction. The composite and metal layers have highly mismatched CTEs in the fiber direction.

Upon cool-down, thermal moments develop along the fiber direction, however bending is resisted via membrane strain due to increase in Gaussian curvature.

With sufficient ΔT, the laminate snaps to an orthogonally oriented cylinder, driven by release of stored membrane strain energy. This occurs in manner similar to the Brazier collapse of a tape measure.

MthMth

Bistability Window

1

2

3

Camera 2

Thermocouple and DIC data aq. PCs

Camera 1

Speckled test article inside oven

Top: Oven test rig with thermocouple and digital image correlation (DIC) system.Above: Curvatures are extracted by fitting a quadratic surface to the DIC-measured point cloud.

Experiment230x230mm CFRP/Al laminate heated to 180°C in oven. Displacements measured with 3D digital image correlation system.

Above: Laminate’s curvature response to temperature change. Dotted lines denote snap-though paths. The laminate’s snap-through temperature during heating is higher than for cooling; the two are separated by a temperature window where the laminate is bistable.


This work addresses the main challenges of describing the multistable behaviour of thin compositeshells for morphing applications. We show how to solve the governing equations by using an accurateand computationally efficient method based on the decoupling of the total strain energy in itsmembrane and bending contributions. The membrane problem is solved in isolation by using theDifferential Quadrature Method, which provides accuracy of results at a relatively low computationalcost. By validating the proposed model against case studies present in literature, we show how thecorrect evaluation of boundary conditions and of the membrane and the bending component of the totalstrain energy influences the stability scenario.

MORPHING STRUCTURES: A REFINED, COMPUTATIONALLY-EFFICIENT SOLUTION OF

THE GOVERNING EQUATIONSEttore Lamacchia, Alberto Pirrera and Paul Weaver

Energy-based semi-analytical model

Supported by

2. Membrane problem solved in isolation by using theiiiii Differential Quadrature Method (DQM)

3. Legendre polynomials (Pij) to approximate theiiiiitransverse displacements. The total strain energyiiiiibecomes a function of the curvatures only.

1. Total strain energy decoupled in the membrane,bending and external contributions

Where A, B and D are give by the CLA and where

where

Results 1. Snap-through Load 2. Multi-mode morphing

[02/902] initially-flat shell. At room temperature the shellexhibits two cylindrical bistable states. The proposed modelallows the snap-through load to be captured with higheraccuracy and with fewer degrees of freedom comparedprevious solutions in the literature (Pirrera et al. IJSS,2010).

[08/908] cylindrical shell. By decreasing the temperature, theshell deforms between two orthogonal cylindricalconfigurations through a series of twisted modes. DQM allowsthe membrane component of the total strain energy to beevaluated accurately and with a low computational cost. This,in turn, allows one to predict the bifurcation points exactly.For comparison see Eckstein et al., Comp. Str., 2014.

Pirrera et al.

Pirrera et al.

4. Stable configurations evaluated by minimising the iiiiiiiiiienergy with respect to the Legendre coefficients qij

and


This work presents an “open” and deployable honeycomb configuration created usingKirigami-inspired cutting and folding techniques. Kirigami is the ancient Japanese art offolding and cutting paper. This technique is used to produce a honeycomb with greaterflexibility than traditional honeycombs. This allows the honeycomb to be used forapplications such as morphing, where traditional honeycombs would be unsuitable.

FOLDABLE MORPHING KIRIGAMI HONEYCOMBRobin Neville, Fabrizio Scarpa

Kirigami ManufacturingCutting and folding operations turn a 2D sheet into a 3D cellular structure:

Supported by

Finite Element AnalysisFinite element analysis was performed toinvestigate the effect of fold angle α onthe mechanical properties of thestructure. It showed that the openhoneycombs’ specific properties arecomparable to that of closed honeycombsfor small α.

Shape MorphingBy embedding wires into the structure, shapemorphing behaviour can be achieved.

Different wires can be tensioned to give differentdeformed shapes, as shown below:

Flat sheet Cut sheet Corrugated sheet Honeycomb

The resulting structure is held together by folds in the material. As a result it is very flexible inbending, but retains some of beneficial out-of-plane properties associated with honeycombs.

Bottom wire

tension

Top wire

tension

Bottom wire

tension

Top wire

tension

No tension

No tension

0.00.10.20.30.40.50.60.70.80.91.0

SpecificE3

SpecificG13

SpecificG23

Perf

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Comparison of open and closed configurations for

α = 15°

CLOSEDOPEN

Composites Processing and Characterisation


Experimental Setup

The development of low-cost bonded assembly of composite aerospace structuresideally requires an NDT method to detect the presence of poor quality bonds. Suchinterfaces can introduce nonlinearity as a result of contact nonlinearity where anultrasonic wave is distorted when it interacts with the interface. Some work has beenundertaken into the fundamental performance of these approaches, but their ability todetect kissing bonds in these complex components is an open question. A techniquethat has shown potential for investigating small material changes is the non-collinearmethod. Its performance and optimisation for composite structures has not beenexplored.

NONLINEAR ULTRASONIC DETECTION OF KISSING BONDS IN COMPOSITE STRUCTURES

Jonathan Alston, Anthony Croxford, Jack Potter

Supported by

Unfatigued FatiguedDifference

Aluminium Testing

Composite Challenges• Attenuative

• Periodic structure

• Anisotropic

Future Work• Build kissing bond simulation experiment

• Speed up process using transducer arrays

• Explore the application of other nonlinear techniques

Linear ultrasonics normally relies upondifferences in the first order elastic coefficient,Young’s modulus, and the density of thematerials to cause reflections at interfaces.

Nonlinear ultrasonics investigates behaviourdue to higher order elastic terms. Kissingbonds have been shown to have nonlinearbehaviour [1]. The non-collinear approach,shown to the right, has the potential to detectthis. This project has focused on creating‘fingerprints’ of the materials’ nonlinearresponse.

[1] Y. Dawei, B. Drinkwater, S. Neild."Measurement of the ultrasonicnonlinearity of kissing bonds in adhesivejoints." Ndt & E International 42, no. 5(2009): 459-466.


The feasibility of embedding vascular networks as internal heat sources in thickaerospace FRP components for curing process optimisation was investigated.Challenges:• Through thickness temperature profile homogenisation;• Exothermic reaction and cure cycle control (heat generation).

THE DEVELOPMENT OF EMBEDDED VASCULAR NETWORKS IN FRP AS ACTIVE/PASSIVE

THERMAL MANAGEMENT TOOLS FOR CURE PROCESSING

Giampaolo Ariu*, Ian Bond, Richard Trask, Carwyn Ward, Yusuf Mahadik

What drives the research?• Validation of the approach as an alternative to

conventional autoclave/oven curing methods;

• Cure optimisation for more complex composite structures, or those of significant size.

Supported by

*[email protected]

Detail of the circulating system for the silicone oil flow across the tubing and the pultruded carbon fibre vascule.

Thermal image of the detail of the aluminium mould and carbon vascule at 150˚C with a silicone oil flow rate of5×10-7 m3s-1.

Heat propagation in the single vascule model for the application of q = 259 Wm-2.

Experimental• Proof-of-concept lab-scale demonstrator;

• Thermal propagation monitoring within in-mould silicone oil (silicone oil as heat carrier through pultruded carbon fibre tube);

Tbeaker = 150, 175, 190˚C; tcure = 30 minutes;

Silicone oil flow rate: 4×10-7, 5×10-7, 7×10-7 m3s-1.

Pioneering achievements?• Ramp rates comparable with oven (2 ˚C min-1);

• Low energy efficiency (≈2%; setup heat losses);

• Potential tcure reduction with higher flow rates and Tbeaker .

Numerical• Finite element analysis (ABAQUS):

Heat transfer within in-mould silicone oil;

Cure prediction of a randomly distributed composite.

Ramp rate comparison of experimental setup (150˚C; 5×10-7 m3s-1), ideal cure cycle andoven run (silicone oil volume of 0.124×10-3 m3).


BMW i3

A major challenge for automotive manufacturers is reducing weight whilstmaintaining enough strength to protect the occupants in a crash. Compositesandwich structures with through thickness reinforcement (TTR) in the form oftufting are seen as a solution to this problem. However, currently there is littleunderstanding of how the TTR behaves or the way the design parameters andmanufacturing process can affect performance.

CRASH SIMULATION OF TUFTED SANDWICH COMPONENTS FOR AUTOMOTIVE APPLICATIONS

Jamie Hartley, Carwyn Ward, James Kratz, Ivana Partridge

Supported by

1. Background• Composite sandwich panels becoming

more popular in automotive applications.• Side impact is a critical design case.• Requires significant energy absorbing

capability.• Need to avoid buckling or disbanding of

face sheets to use sandwich structures.

3. Test Development• Aim to characterise failure of individual

tufts under edgewise compression.• Novel coupon design created to test

individual tuft experimentally.• Tufting process parameters varied to test

possible effects.

4. Results and Validation• Test results show effect of tuft being

captured compared to baseline.

• Little deviation between varied tuftingparameters observed.

• Consistent experimental results validateprocess.

Crushing Failure of Composite Sandwich Panels [Mamalis et al. 2005]

Experimental Test Coupon

15 mm

2. Tufting• Through thickness reinforcement for

dry preforms.

• Friction of preform holds reinforcementin place before infusion.

• Reduced crimp in material preform.

Comparison of Stitching and Tufting Processes [Henao et al. 2010]

Comparison of Testing and Modelling Results

Detailed View of Tuft

Typical Splaying Failure Mode

5 mm

5. Future Work• Extension of testing to dynamic load cases using drop tower.

• Develop supporting modelling approach to help characterise tuft behaviour.

www.bris.ac.uk/compositeswww.bris.ac.uk/composites

Currently the dominant manufacturing route for composites is hand lay-up.Handmade and personally owned tools are ingrained in this process. Theirunstandardised nature is problematic. A novel concept for these tools is beingdesigned and implemented. It is a standardised multi feature tool for laminatorsthat forms an integral part of a composites manufacturing instruction sheet.Presented here is the research focussed on developing laminator’s instructionsheets for use of this concept.

DEVELOPMENT OF LAMINATOR’S INSTRUCTION SHEETS FOR MANUFACTURING AIDS

Helene Jones, A. Chatzimichali, R. Middleton, K. Potter and C. Ward

Supported by

Prototype Instruction SheetsDistributed with the initial prototypes (Figure 2)

•Collected data on how prototype was used

•Using this data to develop instructions that accompany the tool

•To support laminators

87 mm

Eight different geometrical features have been coded:

Forming of a Ply

Moving between Forming Features

Grip

Illustrations for gripping the tool:

Prototype TestingAim is to understand how being used.Prototyped design (Figure 1) being tested:

•Trialled with expert laminator

•200 distributed for trials in industry

•In a training environment

Figure 1 Figure 2

30 cm

Trials With Expert LaminatorCoupled Prototype and Mould Features (Figure 3)•Mould geometry (Figure 4) used

Figu

re 3

(Not

to

scal

e)

Instruction Sheet DevelopmentPrototype use: same in trials and in practice?

•Compare collected data to determine prototype’s features that were used

•Establish was their variation and why

Next Steps•Suggest grips to use feature on prototype

•For a grip couple mould and prototype features for a technique

•Explore how does the prototype impact how decisions around its use are made?

Feature Stages in Technique

Incr

easi

ng S

tage

s in

Tec

hniq

ue

Prototype’s Direction of Motion

Prototype Feature Mould Feature: SurfaceMould Feature: Edge

Figure 4


UK Composite Strategy

Commercial opportunities offered by the

composite industry are at a risk from barriers to market

Shortage of Skills at All

LevelsLack of access to

training and standardisation in delivery of training

Immediate Need for Re/Up

SkillingDouble the composite

workforce by 2015

Possible Solution?

Virtual Reality +

Gamification??

Supported by

LOW COST GAMIFIED TRAINING FOR COMPOSITE LAYUP: A FEASIBILITY STUDY

Shashitha Kularatna, Carwyn Ward & Kevin Potter

Process chosen for the feasibility study is the layup of a carbon fiber composite panel using unidirectional prepregmaterial. The tasks involved were designed into a virtual environment representing the clean room at the Universityof Bristol and presented to users via a head mounted VR headset. Some of the designed tasks are illustrated below.

Hand layup is still the dominant forming process in the manufacture of complexcomposite parts. But, this process is still poorly understood and delivery oftraining to hand laminators is yet to be standardised. In trying to address some ofthese issues, a feasibility study was carried out through this project on the use ofa virtual reality (VR) system as a platform to deliver training to novice laminators.

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Two Testing Stages:1. Technology Acceptance QuestionnaireThis stage involved the evaluation of thetraining aid using a pilot group viasimulator sickness, presence andusefulness questionnaires.2. Knowledge/Skills Transfer TestThis stage involved the evaluation of thetraining aid by comparingknowledge/skills transfer to novicelaminators through the VR training aid totraditional video based training.

VR Headset

Delivery to User

Video Training

VR Training

A task was measured as completed if itwas performed accurately and in thesame order as in the VR simulator.

VR Training for

Complex Geometries

Hand Tracking

(Kinect or Data Gloves)

Haptic Feedback

Drape Simulation

Tools

Pre Shearing

Future Work:


Continuous fibre composites are restricted in complex component productionowing to defects arising from restrictive deformation modes. Highly aligned shortfibre composites are envisioned as an alternative reinforcement system attaininggreater design freedom through enhanced formability by sacrificing performance.

CONTINUOUS FIBRES: CONTINUOUS PROBLEMSMatthew Such, Carwyn Ward, Kevin Potter

Supported by

0

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s (G

Pa)

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Property retention of discontinuous fibrecomposites with varying aspect ratio.

Perf

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Continuous aligned fibres

Relative processability

Relative performance

Highly aligned

short fibres

Unaligned short fibres

Performance and processability ‘sweetspot’ of highly aligned short fibres [1].

Next Steps

Development is needed to create a testing regime by which to compare discontinuous material systems in terms of performance and processability.

Aligned short fibres allow for longitudinalin-plane extension during forming.

Processability Gains

Performance Loss

Relative Merits

1. M. Such, C. Ward and K. Potter “Aligned Discontinuous Fibre Composites: A Short History” Journal of Multifunctional Composites, 2 (2014) 113-126

Quantifying Formability

Forming is normally investigated qualitativelyby investigation of defects induced duringforming. A tetrahedron tool is diaphragmformed in order to mimic high volumeproduction of a complex component.

The resulting laminate is sectioned to create4 point bend specimens for curved beamstrength tests, conforming to ASTM D6415.Strength results are then compared with‘pristine’ coupons created from a radius tool.

This will allow for quantitative investigation ofthe property reduction from inclusion of acomplex geometry feature.

6.4mm

75mm

100mm


This study explored the combining of discontinuous scraps and through-thicknesstufting for the purpose of their use in automotive panels. It found that an idealisedcombination of discontinuous scraps and tufting can improve energy absorption relativeto untufted forms for simplified layup configurations, however, overall performance wascompromised in comparison to highly aligned and organised layup’s of continuousmaterials.

INVESTIGATING THE FEASIBILITY OF THROUGH THICKNESS TUFTING WITH DISCONTINUOUS CARBON FIBRE SCRAPS

Xun Wu, James Kratz, Carwyn Ward, Ivana Patridge

Supported by

Specimen Design & Manufacture:

0O

(b) Taper overlap (50 and 25 mm)

0O

(c) Half-tile offset overlap (50 and 25 mm)

0O

(a) Ply-drop Overlap (50mm)

Tufted Positions

0o

(d) Tufted on overlap design(a)

0o

Tufted Positions(e) Tufted on overlap design(c)

Tufted Case II (Tufted Half-tile overlap)

• Linear stress-strain relation, stepwise load drop

• Decreased energy absorption with tufting, but load drops in a more controllable mannerTufted Case I (Tufted ply-drop overlap)

Results:All specimens were tested under four-point flexure.

3000 µε

1000 µε

• Two types failure: brittle failure and gradual failure

• Average 40% increase in failure strain

• 42% increase in energy absorption

• Delamination initiated from ply-drop, stopped at tufts and propagate into next plies

• Tufts bridging crack

-2.7

4.0

-19.9 -11.7 -9.0

4.4 5.40.2

36.742.0

-40

-30

-20

-10

0

10

20

30

40

50

Strength modulus Elastic strain Failure strain EnergyAbsorption

Tuft

ed P

rope

rtie

s ch

ange

(%

) Half-tile overlap

Ply-drop overlap

Tufted

Un-tufted

Resin pocket fracture Delamination

12

34

tufts

Resin pocket fracture

A

B

Delamination

A

B

12

3 4

Tufted

Un-tufted

Tufted

Un-tufted

TuftsTufts

Delamination initiated from Ply-drop

Compression fibre fracture


20mm delamination


Tensile fibre fracture

Tufted

Un-tufted

• SGL automotive UD CF dry fabric(0.3mm) with Momentive 935/936Epoxy by resin infusion

• Three different overlap strategies &two tufting strategies

• Kevlar tufts, 4mm tuft pitch by12.5mm spacing


Tow steering is the most critical capability of modern automated materialplacement machines, for increased part complexity and production volume in thefield of composites manufacturing. The novel concept of Continuous Multi TowShearing offers the potential to dramatically increase fibre steering capabilities, byutilising the material shear deformation. In this project a complete simulator isdesigned and built for this technology, in order to benchmark its performance.

AUTOMATED HIGH-VOLUME PRODUCTION OF COMPLEX COMPOSITE PARTS: CMTS (Continuous Multi-Tow Shearing)

Evangelos Zympeloudis, Kevin Potter, Paul M. Weaver, Byung Chul Kim

• Test steering radius: 200 mm Test max. shear angle: 30 degrees

Supported by

Importance of Tow steeringTow steering allows for:• Lay-up in complex doubly curved moulds• Production of Variable Angle Tow Laminates

Continuous Multi-Tow Shearing (CMTS)• Contrary with AFP/ATL the material width does

not affect steering capabilities. By utilising a tape with multiple tows, high shape complexity and high production volumes can be achieved.

• To shear tows continuously:CMTS Simulator• 4 axis Cartesian bed (XYZ + rotational A)• CMTS Head Mechanism

Benchmarking Tests (ongoing work)

150 mm

[1] B.C. Kim et al, Multi-Tow Shearing Mechanism For High-Speed Manufacturing of Variable Angle Tow Composites[2] P.M. Weaver et al, Buckling Of Variable Angle Tow Plates: From Concept To Experiment[3] B.C. Kim et al, Continuous Tow Shearing For Manufacturing Variable Angle Tow Composites

[2]

[1]

[3]

Under development for TRL3

Design, Build and Test


The aim of this project was to design, manufacture and test a UAV wing torsionbox-beam demonstrator subjected to an offset-transverse load. The wing will befixed to a test rig so requires the inclusion of leading and trailing edge joints, inaddition to wing-tip rib lug to which the load will be applied.

The project span covered; materials testing, design checks, manufacturingdevelopment, inspection, structural testing and results analysis. This encouragedcritical thinking and the application of student understanding and analysis ofcomposite design and manufacturing in the context of a high-performancecomposite structure.

DESIGN, BUILD & TEST

ACCIS CDT Cohort 2014

Structural Requirements:• Wing deflection must not exceed 100 mm at limit load.

• Wing rotation must not exceed 1.5° at limit load.

• Fibre dominated failure must not occur below ultimate load.

• Global or local buckling must not occur below ultimate load.

• Must withstand an impact of up to 15 J at any position along the wing by ensuring adequate reserve.

• Wing weight must be <4 kg.

Supported by

UAV WING TEST DEMONSTRATOR

Supervisors: Ian Farrow, Carwyn Ward

Circular curved rear spar for flap integration ϕ ≈spar height at TE

Front spar only for limited span at root

Rib extension at TW up to diameter of rear spar curve

Material and Manufacturing:• The available materials were restricted to carbon and glass fibre pre-preg.

• The critical design drivers are for a lightweight, robust construction with a low-cost ethos without compromising the structural performance.

• Any manufacturing route is permitted as long as it is within cost, time and materials constraints.


Team Mitchell’s design incorporates a channelsection and pad up area at the route to enablethe loads to be transferred through the joint.The chosen manufacturing route uses aninternal foam mould, around which the prepregcould be wrapped before bagging and curingwith electric blankets.

TEAM MITCHELL: UAV WING TEST DEMONSTRATORChrysoula Aza, Diego Bracho, Maximillian Dixon, Robert Iredale,

Rujie Sun and Mat TolladayDesign• Design minimises weight whilst meeting the

structural performance criteria. • Wing stability is the most critical aspect – a foam

core is used to support the outer laminates.• Woven glass layers used in the wrap where

stresses are lower.• Unidirectional carbon layers used in the lugs, pad

up and channel section, the critical areas of the wing.

Supported by

Analysis• Design analysed using both hand calculations and finite element models.• Methods used to determine reserve factors for stiffness, strength and stability.

Manufacture• Prepreg plies are wrapped around internal foam mould, before vacuum bagging and curing.• Biggest manufacturing challenge is to create internal voids while preventing skin wrinkling.

DeflectionMaximum = 56.9mm

Stress (S11)

BucklingBuckle Load =1247 MPa

Foam core shape

CAD model outline

Channel section laid up in female

mould.

Foam cut with hot-wire cutter.

Composite wrapped around mould and vacuum bagged.

Ribs cured separately and post bonded.

Channel section bonded into mould.

Pad up

Lug and channel section

Wrap


Team Smith employed a hand lay-up approach coupled with a vacuum baggingand heated blanket method to generate the required structure. Female mouldswere used to obtain the required shape, high-quality surface finish and ease ofmanufacture and assembly to meet the weight requirement.

TEAM SMITH:

Iryna Gagauz, Ashwin Kristnama, Rhys Tapper, Logan Wang, Callum White

Supported by

UAV WING TEST DEMONSTRATOR

Design Requirements•Weight<4kg.•Deflection <100mm.

Finite Element Analysis•After initial calculations, Abaqus was used to model the wing for validation.•Static analysis for deflection (Figure 1).•Buckle analysis for buckling eigenvalues (Figure 2).

Final Design •Woven glass fibre for the wrap, with foam sandwich panel on trailing edge.•Unidirectional carbon fibre for the rail.•Thick quasi-isotropic channel section.•Foam web between rails.•QI ribs at either end.

Manufacturing•Wing skin made of two parts using female tools (Figure 4).•Cured at 80°C for 4hr.•Ribs use a male mould with tabs to aid in adhesive application.

Figure 2 Buckling Analysis.

Figure 1 Static Analysis.

Top half

Bottom half

Channel Section

Figure 4 Trial wing section

Figure 3 Exploded wing design.

EPSRC Centre for Doctoral Training in Advanced Composites for Innovation and Science

University of Bristol, Queen’s Building, University Walk, Bristol, BS8 1TR, UK

www.bristol.ac.uk/composites/cdt

4th ANNUAL CONFERENCE OF THE CDT IN ADVANCED COMPOSITES ... · CDT IN ADVANCED COMPOSITES FOR...

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