cdtin advanced composites forinnovation and · pdf filecdtin advanced composites forinnovation...

Tuesday 5th April 2016University of Bristol, Queen’s Building, University Walk,

Bristol, BS8 1TR, UK

5th ANNUAL CONFERENCE OF THE

CDT IN ADVANCED COMPOSITES FOR INNOVATION AND SCIENCE

POSTER BOOKLET

Multifunctional

Composites and Novel

Microstructures

Advanced curing for on-platform repair of aerospace composite components by external

magnetic fieldsGiampaolo Ariu, Bhrami Jegatheeswarampillai, Ian Hamerton, Dmitry Ivanov

The investigation of effective through service re-manufacturing technologies foron-platform repair of propulsion systems is of interest for aerospace applications.The research focuses on the manipulation of short fibres such as carbonnanotubes (CNTs) through external magnetic fields for advanced curing purposes.

Methodology

• Creation of “high conductivity connections”within composite structure.

• Localised heating for more uniform overallcuring process.

• High conductivity connectors: nanotubes

aligned towards applied field.Schematic of composite inner structure for fibre alignment byexternal energy fields.

Modelling

Modelling• Abaqus/Python model: modelling of realistic

clustered CNT configurations.• COMSOL 3D model for MWNT distribution.

Experimental• Magnetic analysis of Ni/Co/Fe plated MWNTs

(VSM and AC setup at Cardiff University).

Future work

MATLAB: CNTalignment in epoxy

Cylindrical fibres.

Stokes flow before cure. Gravity neglected.

Uniform DC field.

Higher 𝐵𝑂𝑚𝑖𝑛 for increasingar (<100).

COMSOL: Thermal + AC induction heating

AC cooled coil.HexPly® 8552 + metal coated MWNT (ar =10).No external heat source.

AC design parameters: I = 100 A; f = 180 kHz.Model shows a uniform T-field generated in CNT composite solely bymagnetic field.

MATLAB results (left) and COMSOL induction heating model(right: I = 100 A, f = 180 kHz and t = 1h).

Experimental

Magnetic MWNT alignment in epoxy

DC electromagnet (no

cooling): B = 0.5 T. PRIME 20LV + 1 vol.% of

as-received MWNTs

(ar>1000 or ≈ 10).

Relevant agglomeration. Higher alignment at low ar.

Metal coating of MWNTs

TEM of commercial Ni-coated MWNT andNi-plated MWNT.

Commercial coating: inefficient and weak. Plating: more uniform wall coating, but dominantagglomeration.Ni-plated MWNTs can align under lower DC fields.

DC electromagnet (a); SEM of low aspect ratio MWNT in epoxy after DC field (b);commercial Ni-coated (c) and Ni-plated (d, e) MWNTs; (f) Ni-plated and COOH-MWCNT alignment after different applied DC fields.

(a) (b)

H

(c)

200 μm

Unit

cell

Copper

coil

Water

cooling

channel

High

conductivity

connections Field

aligned

fibres

Field

aligned

fibres

Composite

fibres (e.g.

0-90˚

orientation)

Randomly

arranged fibres

in resin

(d) (e)

(f)

www.bristol.ac.uk/composites

Supported by


4D materials are materials that shapechange in response to a stimuli. This stimulicould be temperature, light, chemical or timeitself. This work uses hydrogels, high watercontent plastics, to create shape changingmaterials with pre-programmable and re-programmable transformations. Thesesoft and wet shape changing materials areideally suited to applications involvinginteractions with biological systems,including the fields of biomedical, soft-roboticsand biological sensors.

4D MaterialsProgramming shape change into hydrogels

Anna Baker*, Duncan Wass+ and Richard TraskϮ*[email protected]

+Chemistry (University of Bristol), ϮMechanical Engineering (University of Bath)

Supported by

Programming

XY PlotterCation Pen

+3

+3

+3

+3

+3

Concept

LocalisedPatterning of Metal Cations

No Swelling in this Area

Fold Created as the Rest

Swells

Smart Hydrogel

Hot

Metal Cation

Cold

Water

Future Work

More ComplexShape Change

4D Printing

Demonstration

HotPrinted Cold


3D printed elastic honeycombs with tailorable shock absorbing properties

University of Bristol: Simon Bates*, Ian Farrow, Richard Trask

RNLI: Holly Phillips, Iain Wallbridge

Supported by

To ensure crew members of small high speed craft do not suffer from dangerouslevels of whole body vibration (WBV), the unpredictable oscillations and waveimpact loads must be attenuated. In such vessels, mechanical spring-dampersystems cannot be retrofitted and foam paddings provide insufficient protection tocrew members who are required to kneel on deck. This work describes thedevelopment and experimental analysis of thermoplastic polyurethane (TPU)honeycomb structures which effectively absorb the energy from impact loads andprotect individual crew members, taking into account their weight and positioningwithin the craft.

Multiple densities

3D printed TPU honeycombs

Auxetic honeycombs

Hexagonal honeycombs FDM 3D printer

*[email protected]

Experimental data

*0.5

*0.37

*0.26

*0.5

*0.37

*0.26

*0.5

*0.37

*0.26

*relative density, ρrel

a) The design and; b) collapse behavior of a 3-stage graded honeycomb. c) The stress strain behavior; d) energy absorption profile and; e) efficiency of this structure are shown alongside structures with uniform density. The average

relative density of the graded structure is 0.37a)

b)

c) d) e)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Str

ess (

Mpa)

Strain

Foam sample

Ninjaflex hexagonal RD=0.27

Conclusions

Optimum energy absorption

Optimum energy absorption

• The design freedom of 3D printingallows for functional tailoring

• Grading structures allows for atailored energy absorption profile

• Superior energy absorption tobenchmark closed cell foam

Honeycomb absorbs more energy whilst transferring

lower stress


UV-Responsive Thermoplastic Liquid Crystal Elastomer

Future Work

• Full characterisation of polymeric material.

• Attempt extrusion of filament.

• Measurement of UV-triggered shape change.

Programmed shape change by UV-responsive liquid crystal elastomers

Laura Beckett, Richard Trask, Annela Seddon, George Whittell and

Ian Manners

Supported by

Liquid Crystal Elastomers

Liquid crystal elastomers (LCEs) are materials capable of programmed shapechange on exposure to an external stimulus. Consisting of liquid crystal mesogensattached to a polymer backbone, a change of order on a molecular level inducesdeformation. A thermoplastic LCE should be possible to extrude, giving a route toUV-active filaments that could be utilised in 3D printing.

Nematic Isotropic

Overall a macroscopic contraction/elongation is seen.

x=133y=2z=124

The liquid crystal mesophase switches from an ordered nematic, to a disordered isotropic phase.

When mesogens are attached to a flexible polymer backbone, the polymer chains transition from a stretched to a spherical conformation as order decreases.

LC =

A reversible change in configuration of the mesogen from its rod-like trans isomer to its bent cis isomer can be induced by UV irradiation.

UV-on

UV-off

• A synthetic route to the polymer shown has beendeveloped.

• Unlike the majority of LCEs no covalentcrosslinking is required – meaning processing byextrusion to form a fibre is possible.

• UV-irradiation should lead to reversiblecontraction along the fibre direction.


Photonic crystals are periodic ordered microstructures, built from dielectricmaterials, with a periodicity in the scale of visible light wavelength (~200-700 nm).Through rational design and smart tuning of the PC periodicity it is possible to tailorthe color exhibited by these materials. The main objective of this work is to designand assemble photonic crystal structures based on colloidal self assembly and silicasol-gel chemistry.

Polychromatic composite structures

Diego Bracho, Richard Trask, Annela Seddon

Supported by

20°C1-2 weeks

400°C5h

Deposition Calcination

Figure 1: Schematic illustration of inverse opal assembly by colloidal self assembly

Evaporation

Figure 2: SEM imagedisplaying cross section of aSiO2 inverse opal (1000 nm)

10 μm

Conclusions and future work

• Silica inverse opals of different pore sizes were fabricated using a vertical depositionmethod in a single-step co-assembly of polystyrene colloids in a silica precursor solution.

• These exhibit a face-centered cubic structure (FCC), with the (111) plane oriented at thesurface of the structure.

• Future work will include a detailed study on the photonic bandgap tuning by liquidinfiltration, using different refractive index liquids, and stimuli responsive polymer gels.

Figure 3: Photographs of prepared silica inverse opals and silver coated silica inverse opals

240 nm 500 nm 1000 nm

Inv.

Opal

Inv.

Opal

+ A

g c

oating

Experimental

Figure 4: SEM images from SiO2 inverse structurestemplated from different colloid diameters (φ)

10 μm

φ=240 nm φ=500 nm

φ=1000 nm φ=1000 nm


Use this area for Introduction or Abstract, delete if not required.

Use WHITE text, 36pt Verdana, fully justified and non-bold (except for highlightingwords)

Composite protection

Mark Hazzard, Paul Curtis a, Lorenzo Iannucci b, Stephen Hallett and

Richard Trask c

Supported by

a, b: Imperial College Londonc: University of Bath

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.

ManufacturingGel 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

0/90 Tensile Testing

• Custom specimens to avoid slip and delamination at grips.

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

20 MPa

20 MPa

10 MPa

30 MPa30 MPa

10 MPa

0

100

200

300

400

500

600

700

800

0 1 2 3 4 5

Str

ess

(MP

a)

Ɛs (%)

20 MPa

20 MPa

0.1 mm/s

1 mm/s

Fibre pull-in at rear of loading

tab

Intra-laminar shear and fibre re-alignment

Ɛc

Ɛs

Future WorkTensile 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.

Classical Impact Behaviour

Model with Boundary Capture Modes of Failure

±45 Shear Testing

• 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.

10 MPa

20 MPa

30 MPa

10 MPa

30 MPa

30 MPa

0

5

10

15

20

25

0 0.2 0.4 0.6 0.8 1 1.2

τ1

2[M

Pa

]

ɣ12 [rad]

1

2

3

45

6

θ = 65° after spring-back

Through thickness


3D printing with ultrasonically arranged microfibre reinforcement

Thomas Llewellyn-Jones, Bruce Drinkwater, Richard Trask

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

Results

• Glass microfibres align along acousticpressure nodal planes.

• Selective resin curing achieved.

• Aligned fibres extend to edge of printedpart.

3D Printing Process

• Ultrasonicmanipulation rigattached to FDMstyle printerbed.

• Printer extruderhead replacedwith focusedviolet (405nm)laser module.

Alignment Process

• Fibres dispersed in UV curing resin.

• 2MHz counter-propagating wavefrontsproduce standing wave field.

• Glass microfibres align along theacoustic pressure nodes. Conclusions

• Acoustic manipulation combined with SLAstyle 3D printer can produce parts withpatterned microfibres.

• Complex microstructures can beimplemented.

• Dynamic rearrangement ofmicrostructures can be performed mid-layer.

Glass microfibres aligned within 3D printed part.

Schematic representation of printing and alignment processes

Optical microscopy of glass microfibres before (left) during (middle) and after (right) ultrasonic alignment.

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 3D printed parts with oriented short fibrereinforcement.


4D fibrous materials: characterising the deployment of paper architectures

Manu Mulakkal, Richard Trask, Annela Seddon, George Whittell and

Ian Manners

Diffusion (dominant) and capillary driven deployment in different kinds of paperfolds were investigated and characterised. The results show the clear role ofhydration, water transport and the interaction of hydrogen bonds within the fibrousarchitecture driving the deployment of the folded regions. The importance of fibrevolume fraction and functional fillers in shape recovery upon deployment was alsoobserved and confirmed. The design guidelines arising from this study will helpinform the development of synthetic fibrous actuators for repeated deployment.

Affiliations: ACCIS, School of Physics and School of Chemistry

Supported by

Origami Deployment Sequence

0

500

1000

1500

2000

2500

15 25 35 45 55 65 75

Actu

ation T

ime (

s)

Temperature (°C)

Printer paper 90 gsm Lokta 60 gsm Lokta 30 gsm Seki 30 gsm

0

50

100

150

200

15 20 25 30 35 40 45 50 55

Fold lines

Fold Recovery on Drying

Printer paper

(Filler )

Hand made

(Filler )

*for both directions* Average std.dev

1 44.60 12.89

2 42.83 8.67

3 33.31 9.18

4 39.05 14.66

5 39.02 7.22

6 44.82 11.30

0 s 15 s 22 s 34 s

Deployment sequence (L-R) of the folded profile.

Cracks formed in printer paper and development of low resistance flow paths

Microscopic histology of fold creation in handmade paper

Paper architecture with filler Paper architecture without filler

20µm 100µm50µm

15 mm

90 gsm 60 gsm 30 gsm 30 gsm


Flexible pressure sensors are crucial components of next generation wearabledevices to monitor human physiological conditions. This paper investigatesoptimisation designs of a capacitive pressure sensor to improve its sensitivity andtactility. The effects of different electrode structures on capacitance are comparedto obtain an optimal pattern. Then, a pyramid dielectric structure is designed toimprove pressure sensitivity as well as tactile sensation. Finally, a sensor array isfabricated and using human skin as the other electrode is demonstrated to bemore sensitive to applied displacement.

Designs of capacitive pressure sensors for wearable device: patterns and sensitivity

Rujie Sun, Jonathan Rossiter, Richard Trask

Supported by

• Optimal electrode configuration;

• Pyramidal-shaped dielectric;

• Sensor array fabrication.Fig. 1. Schematic of the designed capacitive pressure sensor.

ElectrodePressure

Skin

Fig. 2. The pressure sensitivity basedon different sensor configurations.

Fig. 3. Sensor array with human skin as theother electrode (a), test results over time undertwo electrode sizes (b).

Micro scale manufacturing techniques; different structural patterns and parameter

optimization for the dielectric; resistive pressure sensor for comparative study.

(a)

0 1 2 3 4 5 60

0.5

1

1.5

2

2.5

3

3.5

Time/s

Cap/p

F

Small electrode

Large electrode(b)

Sensor Designs

Experiments and Results

Future Work

Design, Analysis and

Failure


Aeroelastic performance controls wing shape in flight and its behaviour undermanoeuvre and gust loads. Controlling the wing’s aeroelastic performance cantherefore offer weight and fuel savings. In this work, the rib orientation and thecrenellated skin concept are used to control the wing deformation. Bothexperimental and modelling results show that the rib and crenellation orientationcan influence the wing’s bend-twist coupling and its natural frequencies.

Exploring bend-twist coupling due to geometric features on un-tapered wings

Guillaume Francois, Jonathan Cooper, Paul Weaver

Supported by

The impact of varying the rib/crenellation orientation on the tip twist and tip displacement under static loading is investigated using:

•High Fidelity Finite Element (Modelling)

•3D Printed Wing and DIC measurementmethod (Experiment)

Concepts Explored

Structural Arrangement: Rib/Spar Orientation

Crenellated skin: Skin of varying thickness

Methodology & Results Results - Static Tip Load

Tip

Tw

ist

(Degre

es)

Avera

ge T

ip D

eflection (

mm

)A A

RibSpar

Rib/Crenellation Orientation (Degrees)

Rib/Crenellation Orientation (Degrees)


Ingestion of small and hard particles at high speed causes foreign object damagein gas turbine engines. With increasing usage of composite components and theirrecent introduction to aircraft engines, understanding the effect of FOD oncomponent strength and structural integrity has become a critical activity.

Effect of foreign object damage on composite aerofoils and structures

Ashwin Kristnama a, Michael Wisnom a, Stephen Hallett a,

David Nowell b

aACCIS, University of Bristol, bUniversity of Oxford

Supported by

Impact damage visualisationsTesting procedure

Impacted laminates: low speed (top left) and high speed (top right)1 mm thick high speed impacted laminates: hit at 45°to LE (bottom

left) and TE (bottom right)Experimental setup: high speed impact (left)

and low speed impact (right)

Results and discussion

0

200

400

600

800

1000

1200

0 5 10 15

Failu

re s

tress/

MP

a

Impact energy/ J

High speed

Low speed

Baseline

• 59.8% knockdown in residual tensile strength for 45°LE impact on 1mm thick laminates

• Difference in threshold impact energies between the high/low speed impact conditions

• Influence of specimen and test configurations on delamination size along the laminate

• Normalisation parameter between the two impact conditions – impact energy/force?

• Future work on machined notches, fatigue test post-impact, finite element modelling

0

200

400

600

800

1000

1200

0 10 20 30 40 50

Failu

re s

tress/

MP

a

Delamination length/mm

1mm thick

2mm thick

45° LE impacts

Impact configuration at 45°to the LE

Trailing edge (TE)Leading edge (LE)


Performing rapid multidisciplinary evaluations—involving aerodynamics, structuraland flight mechanics—at the early stages of aircraft wing design is currently achallenge. Ongoing research focuses on developing a robust, multilevel optimisationstrategy for the aeroelastic tailoring of composite wings, including uncertainties inthe design parameter space.

Two-level aeroelastic tailoring for composite aircraft wings

Muhammad Othman, Jonathan Cooper, Alberto Pirrera, Paul Weaver

Supported by

Approach OverviewA two-level aeroelastic tailoring approach is adopted. The first level aims at minimising thestructural weight with the wing subjected to multiple load cases, with stress, buckling andaeroelastic constraints. The design space is then expanded in the second level to includeuncertainties in the parameters defining the structural and material properties.

2nd Level Tailoring

• Polynomial Chaos Expansion enables efficientquantification of uncertainty in wing design.

• Objective: Minimisation of probability foroccurrence of instability at design airspeed.

• Deterministic and robust design comparison.

• Design cases:i. Flutter/Divergence only.ii. Flutter/Divergence and gust response.

Analysis Mean instability speed (m/s) Prob. of failure

Monte Carlo Simulation (MCS)

371.4 0.0291

Deterministic design 374.0 0.0334

Robust design 544.3 1.0e-6

Optimal thickness variation Buckling results Stress tensor variation for optimal design

Comparison of instability speed PDFs

Benchmark wing model

Mean instability speed and probability of failure at design speed

VD=330 m/s

1) Deterministic design

2) Robust design

• Benchmark wing model with aspect ratio 10.• Static manoeuvre load cases.• Wing skin and spar laminates optimisation.• 328 design variables (ply thickness, t, and angle, θ).• Optimised solution used as input to 2nd level tailoring.

1st Level Tailoring

• Optimisation problem:


Single Fibre Response

• Very high strain of 15%

• Metallic-like ductility

Carbon fibre composites commonly exhibit lower failure strains in compressionthan they do in tension. This is in spite of the inherent properties of carbon fibres,which can be ductile and achieve impressive strains in compression. The aim ofthe project is to overcome the mechanisms causing early failures in compression.

Realising the potential of carbon fibrecomposites in compression

Jakub Rycerz, Michael Wisnom, Kevin Potter

Carbon Composites Strength

• Composite up to twice as strong in tension

• Compressive strength has apparent limit

• Compression strength seems quiteindependent of tensile performance

• Suggestion of a different failure mechanism

• Low compressive strain not a fibre property

Supported by

Stability Governs Failure

• Fibres never perfectly aligned

• Shear and misalignment increase with load

• Loss of equilibrium causes critical instability

Objectives:• Develop a test to investigate non-linearity at high strains• Model the behaviour to establish the parameters affecting the instability• Explore materials that suppress the instability

[1] M. Ueda, W. Saito, R. Imahori, D. Kanazawa, and T.-K. Jeong, “Longitudinal direct compression test of a single carbon fiber in a scanning electron microscope,”Compos. Part A Appl. Sci. Manuf., vol. 67, pp. 96–101, Dec. 2014.

[2] M. Wisnom, “The effect of fibre misalignment on the compressive strength of unidirectional carbon fibre/epoxy,” Composites, vol. 21, no. 5, pp. 403–407, Sep. 1990.

Sourc

e: [1

]

Sourc

e: [1

]

Source: [2]


The aim of this study is to experimentally investigate the open-hole tensileresponse of pseudo-ductile thin-ply angle-ply laminates. It is shown that withproper selection of pseudo-ductile strain to initial strain ratio, notch sensitivity isreduced and at least 96% of unnotched yield strength can be attained.

Open-hole response of pseudo-ductile thin-ply angle-ply laminates

Xun Wu, Jonathan Fuller, Michael Wisnom

Supported by

Initial Design:

Improved Design:

Background:

Pseudo-ductile tensile stress-strain responses havebeen achieved in using thin-ply angle-ply withcentral unidirectional plies concept. Periodic fibrefragmentation in the central 0° plies and theirdispersed local delamination introduce pseudo-ductile strains.

• Skyflex USN020 prepreg with layup (±265,0)s.

• Pseudo-ductile to initial strain ratio: 1

• Attained 65% unnotched yield strength

• Brittle net-section failure

• Insufficient stress and strain redistribution

• Pseudo-ductile to initial strain ratio: 3.5

• Attained 96% unnotched yield strength

• Non-linear stress-strain responseobserved

• Fragmented central UD plies anddispersed delamination released stressconcentration and redistributed strain.

Incre

ase p

seudo-d

uctile

stra

in ra

tio

• Angle ply (Skyflex UIN020) and UD ply(YSH70) with layup (±252,0)s

Loading Direction

Loading Direction

(J.D.Fuller, 2014)

Notch Sensitive

Notch Insensitive

Initial strain

1

Pseudo-ductile strain3.5

Net-section strength: 620 MPa, 96% of unnotched yield strength,

Kstress = 1.03.“Notch Insensitive”

Intelligent Structures


Design optimization is carried out for a morphing trailing edge using honeycombcore of axial variable stiffness. Introducing variable stiffness materials intomorphing structures leads to a reduction in the actuation requirement and enablestailoring of the geometry of the deflected morphing trailing edge. Enhancedaerodynamic and aeroacoustic performance of aerofoils fitted with such devices isachieved. The optimization process successfully identifies the required stiffnessvariation in the honeycomb core to obtain the desired morphing profiles.

Design optimization of a morphing trailing edge using variable stiffness materials

Qing Ai, Paul Weaver, Mahdi Azarpeyvand

Supported by

Background

• Extended design space of morphingtrailing edge and enhanced aerodynamicand aeroacoustic performance of aerofoilscan be obtained using variable stiffnessmaterials

• Design optimization scheme seemsnecessary to bridge the morphing profileand structural design

Methodology

• An efficient beam model based on Rao’slayer-wise sandwich beam [1] model isdeveloped to facilitate the designoptimization process

• A hybrid optimization formulation basedon Matlab combining Genetic algorithmand Nelder-Mead algorithm to search theoptimal solution

• Fluid structure interaction is considered toaccount for the effects of the aerodynamicload on the structure design

Results

• The current model provides accurateprediction of the desired stiffnessvariation in the honeycomb core forprescribed optimal morphing profile

Future work

A hardware proof-of-concept demonstratorwill be built for furthermechanical tests.

Reference

[1] Rao D.K. Static response of stiff-cored unsymmetricsandwich beams. Journal of Manufacturing Science andEngineering 1976; 98:391-396.

Figure 1. The staticaeroelastic analysisprocedure

(a)

Figure 2. Optimization results of given morphingprofiles: (a) the optimised deformation shape ofthe morphing trailing edge; (b) the optimised corestiffness variation

(b)


A novel actuator for a wearable robotic device assisting elbow motion has beendeveloped. The actuator combines current mechatronics with compositestructures with nonlinear stiffness characteristics. Nonlinearities are exploited toobtain compliance, force and position control authority, as well as powerefficiency: all key features for the successful design of robotic devices that involvedirect human-robot interaction.

Design optimization of a multistable composite compliant actuator for wearable robotics

Chrysoula Aza, Lorenzo Masia, Paul Weaver, Alberto Pirrera

Compliant actuator

Supported by

Composite structure

Motor

ReAct

Bowden cables

Timing belts

front back

stripspoke

L

H=

2R

Ζ

φ

θ Δℓ

X

W

ℓ

Results

Design requirements

• Minimising dimensions for space& weight limitations.

• Composite transmission in stableequilibrium at pitch θ = ±45°.(See figure below)

• Maximum axial force F = 50N.

Conclusions

A Pareto front of optimal designs obtained, suggesting:

• Use of anti-symmetric lay-up.

• Fewer plies smaller diameter of transmission.

• Smaller diameter of transmission higher axial forces.

• Plies <3 or >6 are less likely to satisfy all theobjectives equally.

Optimization process

Multi-objective optimization using genetic algorithm.

• Decision variables:

• Composite layup.

• Strips’ stress-free curvatures.

• Diameter of transmission.

• Strips’ length.

• Strips’ width.

• Conventional mechatronictechnology.

• Multistable compositetransmission i.e. doublehelix architecture.

optim

um

www.bris.ac.uk/composites

Intelligent self-actuating composite structures

Michael Dicker, Ian Bond, Paul Weaver, Jonathan Rossiter and Charl Faul

Supported by

a. b. c.

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. e.


Shape-changing structures can reconfigure to provide extended/enhancedfunctionalities, thereby facilitating mass, volume and part count reduction, aperpetual objective across multiple industries. This project develops work onmulti-stable cylindrical lattices capable of adaptive shape change, by investigatingellipsoidal lattices. It is demonstrated numerically that the deformation mechanicsand kinematics of multi-stable cylindrical lattices are applicable to alternativegeometric configurations with non-zero Gaussian curvature, specifically ellipsoids.

Ellipsoidal lattice structures

Maximillian Dixon, Isaac Chenchiah, Alberto Pirrera

Supported by

• Enclosed volume – Capture/containment• Variable aperture – Flow regulating nozzle• Adaptive geometry – Spherical antenna• Tailorable stiffness – Spring/energy absorber

2. Pre-stress 3. Relaxed

Pre-stressed (black) and relaxed (coloured)configurations showing von Mises stress fora lattice of constant pre-curvature.

1. Initial 2. Pre-stress

Initial (black) and pre-stressed (coloured)configurations showing von Mises stress fora spiral of constant pre-curvature.

3. Relaxed 4. Operation

Axial extension of 250 mm

Radial contraction of 200 mm

SHAPE ADAPTATION

Cylindrical Lattice Application Examples

ALTERNATIVE GEOMETRY =ADDITIONAL EXPLOITABLE BEHAVIOUR

Quadrifilar Antenna1

Device Assembly Stages

1. Initial – Spirals manufactured profile2. Pre-stress – Deformation to lattice profile3. Relaxed – Relaxation of assembled lattice4. Operation – Shape Adaptation

1. GM Olson, 2013, doi:10.2514/6.2013-16712. BK Dinh, 2015, doi:10.1109/ICORR.2015.7281244

Robotic Actuator2

Potential Ellipsoidal Lattice Applications


a. b. c.

Stimuli-responsive hydrogels are typically characterised by slow swelling speeds,limited by the rate of water diffusion through the material. This severely hinderstheir potential application in mechanical actuators. One method to increase thespeed of response is to introduce porosity into the material; however, this alsoresults in a decrease in the stresses that the gel can generate. In this study, theeffect of different levels of porosity on the swelling speed and force-strokecapability of a pH-responsive hydrogel are investigated. Power outputs of each gelcan then be determined, allowing optimisation of gel microstructure.

Hydrogel actuators: Porosity and power outputRob Iredale, Michael Dicker, Paul Weaver, Ian Bond, Jonathan Rossiter and Charl Faul

Supported by

Porous, pH-responsive Hydrogels

• Semi-interpenetrating polyurethane/poly(acrylicacid) double network hydrogels synthesized via UVcrosslinking.

• Gel swells in basic solutions. Swelling is reversible.

• NaCl particles of varyingsizes used to create poresin a salt leaching method.

Fig. 1 Schematic describing gel synthesis.

Fig. 2 Explanation of gel swelling process.Fig. 3 SEM images of hydrogel with 220μm pores.

Fig. 4 Stress-strain-power plots for gels of different porosities.

Gel Performance

• The introduction ofporosity (13 μmporogen size) leadsto 31% increase inpeak power.

• However, the stressgenerated is muchlower than the non-porous reference.

Porogen sizePeak power density

(W/m3)Stress (kPa)

Strain (%)

Time (mins)

a. Non-porous 1.16 33.4 40 180

b. 13 μm 1.52 9.3 90 90

c. 220 μm 1.09 6.3 95 90

Conclusion: A hydrogel’s microstructure can be tailored to optimise its performance in terms of stress, strain or swelling time.

.Mat Tolladay, Dmitry Ivanov, Neil Allan and Fabrizio Scarpa

Composites Processing

and Characterisation


Kissing bonds are hard to detect with current ultrasound techniques, which relyupon interfaces causing reflection or scattering, since the two bond faces are inintimate contact. These interfaces are less stiff in tension than in compression sothey behave nonlinearly, which allows another route to detection. This work isfocused on developing the nonlinear method of non-collinear beam mixing tocreate parametric surfaces, called ‘fingerprints’. The features in these fingerprintsmight allow for weak bonds to be identified which would be very useful forproviding confidence in bonded joints.

Nonlinear ultrasonic detection of kissing bonds in composite structures

Jonathan Alston, Anthony Croxford, Jack Potter

Supported by

Frequency ratio

Inte

raction a

ngle

[deg]

Half intensity

0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4

95

100

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Half intensity

Frequency ratio

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raction a

ngle

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0.6 0.8 1 1.2 1.4

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80

90

100

110

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

0.05

Frequency ratio

Inte

raction a

ngle

[deg]

0.6 0.8 1 1.2 1.4

50

60

70

80

90

100

110

1

2

3

4

5

6

Frequency ratio

Inte

raction a

ngle

[deg]

0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5

50

60

70

80

90

100

110

Left:2024-T351 aluminium with loaded interfaceRight: Same but with water in the interface

60 65 70 75 80 85 90 95 100 105 1100.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

0.11

0.12

Interaction Angles

2Nm

4Nm

6Nm

Sample

Detection array

Input transducer

Scattered beam

In the experiment the angles of the input beams andtheir frequencies are varied. The colour of each pixel inthe fingerprint is related to the intensity of the scatteredbeam produced by the combination of those twovariables. The patterns produced are independent of theinput beam intensities, as shown in the solid aluminiumfingerprints above.

Frequency ratio

Inte

raction a

ngle

[deg]

Max intensity

0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4

95

100

105

110

115

120

125

130

135

Maximum intensity

Bolted interface sample andmodelling of interface loading.

CFRP with weakened interface.

Left: 6082 T6solid aluminium Right: Single frequency ratio with varying interface load


Porosity is a common manufacturing defect in composite materials. It can be caused by ineffective debulking or inadequate autoclave curing which leads to air being trapped within the laminate. Porosity has significant effects on the matrix-dominated properties of a composite. Many researchers have investigated the influence of porosity content on the mechanical performance of composites. However the size, shape and location of voids are important parameters often not characterised. The aim of this work was to characterise these parameters and investigate their correlation to interlaminar shear strength.

Effects of porosity on the interlaminar behaviourof carbon/epoxy composites

Iryna Gagauz, Luiz Kawashita, Stephen Hallett

Supported by

10 mm

2 mm

5 10 15 20 2536

38

40

42

44

46

48

50

Max dimension, mm

ILS

S, M

Pa

Batch 1 (temperature = 30C)Batch 2 (temperature = 90C)

r=-0.808

0.2 0.4 0.6 0.8 1 1.236

38

40

42

44

46

48

50

Max effective radius, mm

ILS

S, M

Pa


r=-0.863

0 2 4 6 836

38

40

42

44

46

48

50

Void content, %

Inte

rlam

inar

She

ar S

treng

th, M

Pa


r=-0.858

0 10 20 30 4036

38

40

42

44

46

48

50

Peak of void volume fraction in a layer,%

Inte

rlam

inar

She

ar S

treng

th, M

Pa


r=-0.896

Pressure and temperature controlled curing using hot plates in a testing machine• Batch 1: pressure 0.3 MPa, T=30°C,

post-cure @ 100°C for 17 hours• Batch 2: pressure 0.3 MPa, T=90°C,

post-cure @ 100°C for 17 hours

RESULTS AND DISCUSSIONS

MANUFACTURE DETECTION TEST

Excellent correlation(a) optical micrograph (b) μCT-imaging

Cracks nucleate from and coalesce between voids

Effect of void volume fraction on ILSS

The maximum void volume fraction in a ply provides the best correlation with ILSS

Effect of void features on ILSS

1 2 3 4 5 6 7 8 9 101112131415160

0.1

0.2

0.3

0.4

0.5

Ply number

Voi

d vo

lum

e, m

m3

Peak void volume

Void volume (i.e. effective radius) showeda much stronger correlation than maximumdiameter of a circumscribed sphere.

Effective radius, based on void volume:

Short beam shear test for interlaminar shear strength (ILSS) testing


Understanding the behaviour of tufted sandwich structures in edgewise compression

Jamie Hartley, James Kratz, Carwyn Ward and Ivana Partridge

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 in the form of tuftingare seen as one possible solution to this problem. However, currently there is littleunderstanding of how tufts behave or the way the design parameters andmanufacturing process can affect performance.

Supported by

3. Key Findings

• Loop length appears to have no effect onperformance (SEA), but increasing thenumber of threads does.

1. Tufting

• Through-thickness reinforcement for drypreforms, where friction of preform holdsreinforcement in place before infusion.

Future Work

• Further analysis of column drifting effects,and the effect on energy absorption.

• Develop supporting modelling approach tohelp characterise tuft behaviour.

2. Test Development

• Novel coupon design created to testindividual tuft experimentally.

• Number and length of tufts chosen as testvariables.

Background

• Side impact is a critical design case,particularly for modern battery poweredvehicles.

• Need to avoid buckling or disbonding offace sheets to use sandwich structures inthese energy absorbing applications.

BMW i3 Euro NCAP pole impact test

Tufting manufacturing process

Tuft loops Single tuft test coupon

Single tuft test results

A B C

Tuft Columns before testing

Column DriftColumn stacking

and failure

Drifting behaviour of columns during crushing

• Drifting of resin columns observed,potentially leading to secondary energyabsorption mechanism.


Currently the composites industry is struggling to integrate knowledge from production into design. The industry is operating with an incomplete learning cycle and this is problematic as the industry is looking to grow. This research has focussed on the manual forming process, hand lay-up, performed by a laminator. This process is very often reliant on a laminator’s tacit knowledge. To integrate a laminator’s knowledge, this research is aiming to describe what the interface between manufacture and design could look like.

Using a knowledge base on hand lay-up to describe the interface between design and

manufactureHelene Jones, Carwyn Ward, Kevin Potter

Supported by

Hand lay-up Hand lay-up (Fig.1) is a manual process that involves forming plies to a mould geometry. Ingrained in this process are manual tools that support the hand to form particular geometries. !

Figure 1: The manual process of hand lay-up

Hand lay-up knowledge base From previous research on hand lay-up [1,2,3,4] four variables to describe the knowledge base on hand lay-up have been extracted: • Mould Geometry• Material• Lay-up Task• Tool (Fig.1)

Design: Manufacture interface Currently the design process does not integrate the knowledge base around tools (Fig.2). Fig.3 proposes this knowledge base is integrated using geometry coupling.

Figure 3: Proposed interaction

Figure 2: Current interaction

Design for manufacture There is a need to design aids to incorporate a laminator’s knowledge into the design process. Fig.4 is a prototype for a visualisation to support the interaction proposed in Fig.3. Geometry coupling defines how a tool and mould geometry interact. This visualisation informs a designer when a tool is required to support the hand to form a geometry.

Figure 4: Visualisation to support a designer selecting a tool to form a particular mould geometry

1. L. D. Bloom (2015) On the relationship between lay-up time,material properties and mould geometry in the manufacture ofcomposite components, PhD Thesis, University of Bristol. 2. M. Elkington (2015) The future of sheet prepreg layup, PhDThesis, University of Bristol. 3. R. Dixon (2015) Quantifying the hand lay-up process of wovenpre-impregnated composite sheets to improve productivity, Masters Research Project, University of Bristol.

4. M. Such, C. Ward, W. Hutabarat and A. Tiwari (2014) Intelligent composite lay-up by the application of low cost tracking and projection technologies. In 8th Int. Conf. on Digital Enterprise Technologies.


Hand layup of composites is still poorly understood, though this is improvingthrough the activities of EPSRC CIMComp. Even so, it is yet to be fullystandardised as even two expert laminators tend to layup very basicgeometries in different ways. This can lead to variations in the performanceof the final composite part. By using novel Augmented and Virtual Realitytechnologies, this project seeks to deliver a solution to this issue.

Gamification for improved layup

Shashitha Kularatna, Carwyn Ward, and Kevin Potter

STAGE 1

Laying Up a Flat Panel in Virtual Reality (VR)

STAGE 2

Simulation of Prepreg Shear and Layup Tools

STAGE 3

Complex Shapes and Real-Time Feedback

A VR training aid for composite layup, based in the ACCIS clean

room environment was designed and delivered to users

via a head mounted, smartphone based, VR system.

The tool was trialed against groups with different levels of experience in composite layup

DELIVERY TO THE USER

Vid

eo

Tra

inin

g

VR Tra

inin

g

TESTINGVideo training vs. Virtual Reality training for novice laminators.

[A task was measured as completed if it was performed accurately and in the

same order as in the VR simulator]

Muscle memory reinforcement for laminators in deforming

Prepreg

The “Dibber” is a standardized multi-purpose layup tool designed by Helene Jones at the

University of Bristol

Tools play an important role in draping Prepreg over complex

shapes.

The Oculus Rift can be combined with the Leap Motion controller to train laminators and standardise the layup

procedure of complex composite parts

WORK IN PROGRESSDesign of VR simulators for complex shapes and use of Microsoft Kinect to provide Real-Time feedback to

laminators

Virtual Pin Jointed Net Leap Motion Controller

Supported by


Tufting thread

Resin pocket

Ply-by-ply composite

Cohesive contact

Tufting belongs to the class of Through-the-Thickness Reinforcement (TTR) techniques developed to improve the delamination resistance of 2D composites. It is a single sided stitching technique in which a dry thread is inserted into a dry preform and forms a microfastener once impregnated with resin and cured.This project aims at establishing a complete modelling framework for tufted composites by adopting a multi-scale modelling approach.

Multi-scale characterisation and modelling of tufted composite structures

Camilla Osmiani, Ivana Partridge, Galal Mohamed, *Giuliano Allegri

Supported by

Fig.1 – X-Ray image of single carbon tuft tested in pull-out (NCF composite) and corresponding experimental bridging law and

failure mechanisms.

Fig.2 – High fidelity FE model of a single carbon tuft in 0/90 NCF composite.

Tufted rows

Bridged crack

Fibre bridging

Fig.4 – Double Cantilever Beam (DCB) test of a tufted coupon with 1% areal density of

carbon tufts. Fig.5 – Tufted DCB specimen: FE analysis in LS-DYNA v971 R7.1.2.

Saw-tooth behaviour along tufted interface

Tuft bridging law

Ply-ply interface

Debonding

Tuft fracturesurface

Fig.3 – Calibrated analytical prediction of single carbon-tuft in mode I pull-out.

Single-Tuft Testing

Coupon Tests for Arrays

Micro-Scale FE Models

Meso-Scale FE Models

Analytical Modelling

CohesiveInterface Elements

Elastic deformationof tuft and composite

Debonding andfrictional sliding

Failure

Tuft made of two segmentsof a 2-yarn thread

*Imperial College London

Pre-crackCohesive elements

v

v

Analytical model

Envelopesexp. data


Continuous fibre composites encounter problems with geometrically complexcomponent production due to induced wrinkling and bridging defects arising fromrestrictive deformation modes. These defects restrict productivity and play a keyrole in the structural response of a component which limits the design envelope forengineers. Discontinuous fibre composites may alleviate these problems, owing tothe ability of the material to extend in the fibre direction and localised deformationfor features instead of a global material response. A greater body of work isneeded to understand advantages and limitations of highly-aligned discontinuousfibre composites.

Investigation of formability of highly-aligned discontinuous fibre composites

Matthew Such, Carwyn Ward, Kevin Potter

Supported by

A tetrahedron tool with a highly complex double curved feature has been chosen to assessthe formability of various material systems with double diaphragm forming of an 8 ply QIlayup in order to represent the creation of a corner bracket component. The resultinglaminate is cured in an autoclave and inspected qualitatively for defects.

Discontinuous

Layup heated to ~80°C and held between two silicone

diaphragms

Tool drawn into layup and secondary vacuum applied

Layup cooled and bagged for autoclave cure

The resulting aim is to develop a more quantitative measure of formability. Curved beamstrength samples conforming to ASTM D6415 will be extracted from the laminate andcompared to pristine samples in order to understand the effect of defects in this component.This investigation will inform further development and utilisation of highly-aligneddiscontinuous fibre composites, a greater uptake of which should allow for a higher level ofautomation in composite production.

Excessive wrinkling trapped

autoclave consumables

Continuous

~210mm

Large degree of localised extension

Wrinkling minimised with respect to

continuous component but still

problematic

Large amount of waviness across both

samples

Further Work

Method


Secondary recycling can give composite materials a second operative life as a highvalue product, reclaiming most of the value of the virgin constituents. This projectworked towards developing the first closed-loop recycling method for carbon fibrecomposites. The process involves the separation of thermoplastic matrix andcarbon fibre reinforcement, fibre re-alignment and subsequent consolidation of thereclaimed thermoplastic and fibres. Solvent processing of matrix and fibresresulted in composite tape-type prepreg fabrication however process optimizationis required for improved mechanical properties.

Towards a closed-loop recycling method for short carbon fibre composites

Rhys Tapper, Marco Longana, HaNa Yu, Kevin Potter

Closed-Loop Recycling Process - A cycle which requires no additional material input

after initiation.

Supported by

Impact

Gives end-of-life composites a secondary life in a high value application.

[1] Yu H, Potter KD, Wisnom MR. Composites: Part A (2014).

Figure 1 – Flow diagram of the closed-loop methodology.

Figure 2 – Schematic of the automated part of the recycling process.

Figure 3 – Preform.

Figure 5 – Prepreg.

Figure 4 – Film stacking Impregnation.

• Thermoplastics and Short (3 mm)carbon fibres lend themselves torecycling due to a lack of cross-linking and short length, respectively.

• HiPerDiF alignment method is usedto produce a high level of alignmentfrom liquid dispersion [1].

• Dispersion of fibres in polymersolution introduced to alignmenthead of machine.

Significantly increases carbon fibre composite desirability in industry i.e. automotive.

Fibres from pyrolysis can be incorporated –many tonnes of unused carbon fibre.


Diaphragm forming is a cost-effective method that has been used to manufactureaircraft structures (e.g. wing spar). This technique improves production rate bylaying multiple prepregs to create an uncured laminate first and then forming itinto a desired shape later. However, the ply slippage resistance results in defectsduring this forming method. In this research, a new method using interleavingmaterials to reduce the interply friction was developed, which could effectivelyminimise the wrinkle during low temperature forming, as well as increase thefracture toughness.

Improvement of composite drape forming quality by enhancing interply lubrication

Wei-Ting Wang, HaNa Yu, Kevin Potter, Byung Chul Kim

Supported by

Background: HDF process

Multiple prepregs

Uncured laminate

Place laminate on top of tool

Shape with heat and external pressure

High interfacial friction

Out-of-plane wrinkleWrinkling mechanism

Improvement method

Laminate

Interleaving lubricant

Forming Consolidation

Challenge

ResultsPromote ply slippage

Powder interleaving

Veil interleaving

Non-interleaving

Interply frictional resistance test Drape forming test

Frictional test rig

Increase fracture toughness

Mode-I fracture toughness test

DCB test

Future work• Precision lubrication material deposition

methods.

• Focus on forming complex shape.

• Combine with existing automatedmanufacture processes.

• Transfer this concept to other compositesheet forming methods.


Dijkstra’s algorithm is widely used in weighted shortest path problems in graphtheory. This has been applied in such disciplines as network optimisation andsatellite navigation. Here is presented the application of the algorithm to findingultrasonic ray paths and the corresponding arrival times in composite materials,which can be subject to complex steering due to variations in the fibre direction.This allows the construction of an image via the total focussing method in order tofind defects.

Dijkstra’s algorithm for ultrasonic ray tracing in composite materials

Callum White*, Paul Wilcox, Fabrizio Scarpa

Supported by

FE Dijkstra

Figure 3 Arrival times calculatedfrom FE and Dijkstra

Conclusion

• Dijkstra’s algorithm is a good candidate for calculating arrival times in non-planar anisotropiccomponents

• This should allow the accurate imaging of composite components of non-planar shapes, toallow the detection of defects

• Simulation shows the nature of beamsteering in composite materials

Figure 2 Elastic waves in acomposite cross section

Force input

• Create network approximation ofcomposite material

• Determine edges based on an allowablehop radius and velocity profile (Fig. 1)

• Use Dijkstra’s algorithm to find arrivaltime at each node Figure 1 Velocity phase diagram for

high strength carbon fibre/epoxy

• Using finite element-calculated velocity andarrival times (Fig. 1, 2) can see a closeagreement with Dijkstra’s algorithm (Fig. 3)

Results

Steps

*[email protected]


Through-thickness-reinforcement (TTR) is a method for limiting the delaminationseen in composite components and the debonding experienced by sandwich panelsduring edgewise compression. Tufting is one such TTR with the potential toinfluence failure. Understanding the quality implications of tufting parameters andthe manufacturing process is necessary, but this is not trivial as the tufts areembedded within the panel and have so far been difficult to analyse.

Tufting visualisation and analysisEmily Withers, James Kratz, Ian Hamerton, Ivana Partridge, Carwyn Ward

Objectives• Identify parameters of the tufting process

and their influence• Define tuft quality and if possible an ideal

tuft• Improve/control tuft quality through the

parameters identified

Supported by

Tuft technology

Dry fibre preform mounted on sacrificialfoam

Presser foot compacts preform Needle inserts thread at low tension Friction resists thread retraction causing a

loop to be formed in the preform

MethodologyDevelop test bed to permit visibility of needle

insertion and its effect on the preform

Transparent casing used to make loop

formation visible

Needle insertion controlled by Instron rates

of 100-1000mm/min

1kN load cell measures penetration and

retraction forces

Findings

Aspects of tufting quality:

o fragmentation of the carbon skin filaments

o fragmentation of the foam core

o non-uniformity of the needle path

dimensions

o fibre breakage/movement out-of-plane

Figure 2: Infused, tufted sandwich panel

Figure 3: Test bed in position on Instron

Needle

Figure 1: Loop variation seen in tufted panel

Figure 4: Loop formation in test bed

Results•Tuft formation visible in situ

•Force of penetration seen to vary with the

needle contours and sandwich interfaces

•A quality matrix was developed based on

the characteristic aspects observed

•This as-measured tuft quality correlates to

variation in rate of needle insertion

Further work required to identify additional

quality aspects and control in agreement

with the commercial tufting robot process.Figure 5: Insertion and retraction force data


Automated high-volume production of complex composite parts: Continuous multi-tow shearing

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

In an attempt to improve the productivity of composites manufacturing, theindustry has pioneered the use of automated material placement machines.Although these machines excel in placing fibres in straight lines, their ability toproduce curved paths is extremely limited. The concept of CMTS removes thislimitation while maintaining the potential for high production rates.

Tow Steering

• Structural efficiency through variablestiffness structures

• Lay-up in complex doubly curved moulds

[1] [2]

Limitations of Current Technology

Fibre Buckling Width affects steering abilities[3] [4]

• In plane bending of tapes Defects:

• Minimum steering radius:

• ATL: 6000 mm for 150 mm wide tape

• AFP: 630 mm for 3.175 mm wide tow [3]

Continuous Multi-Tow Shearing

• Exploit material shear deformation

Aim: Develop a material placement head which can produce high quality tow steered laminates at high production rates

Evaluation of Different Materials for CMTS

• Minimum steering radius:

• CMTS: 260 mm for 90 mm wide tape

[1] Coburn et al. 2015 [2] Chauncey Wu et al. 2009

[3] M. H. Nagelsmit et al, 2013 [4] K. D. Potter, 2009

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

-230 -170 -110 -50 0 50 110 170 230

Percen

tag

e o

f R

esin

Area (

%)

X Position (mm)

Resin Pocket Areas vs Position

Tows 1-10

Tows 11-30

Tows 31-40

{Fusible weft yarns cause excessive wrinkling at high shear angles}

{Weft yarns with low tension cause areas of resin pockets}

50 deg40 deg30 deg

200 m

m

50 deg30 deg

• Defect generation- Resin pockets- Local wrinkling- Tow thickness variation

• Process Accuracy- Tape path deviation- Tape boundaries variation

0

Supported by

Design, Build and Test


The aim of this project was to design, manufacture and test a compositeundercarriage beam subjected to compression and an offset-vertical load. Thedesign must consist of a monolithic open-section beam with integral bushes for pinjoints.

The cohort has been split into two teams (Iceman & Maverick) who will compete todesign, build and test the structurally most efficient beam.

Design, Build & Test:Monolithic undercarriage beam

ACCIS CDT Cohort 2015

Structural & Manufacturing Requirements:

• The Y depth must taper by at least 30% at the ends.

• Beam shall not deflect by more than 20mm at limit load.

• Beam shall not rotate more than 5° at limit load.

• Fibre dominated or interlaminar failures shall not occur below ultimate load.

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

• The design shall allow for an impact up to 15J at any random position by ensuringadequate reserve factors.

• Any material or manufacturing route permitted.

• The critical design drivers are mass, cost and ease of manufacture within the timeconstraints of the project.

Supported by

Supervisors: Ian Farrow, Carwyn Ward

Team MaverickTeam Iceman


Key Features• C beam

• Made from unidirectional and woven prepreg

• 5mm maximum thickness

• 10mm inner-radius of curvature

• 30% taper on one side of web

Team Iceman: Undercarriage beam

Andrés Rivero, Olivia Leão, Robert Worboys, Tamas Rev,

Vincent Maes and Yanjun He

Design

• Analytically and numerically calculated

• Beam is stability driven

• Local ‘pad-up’ sections around the holes

• Steel bushings at centre and end holes

Manufacturing

Supported by

Male Mould Hand Layup Autoclave Cured

• Styrofoam trial mould

• Tool block final mould

• 100⁰C for 3 hours

• 7 bar pressure

RF = 1.08

Deformation Analysis Buckling Analysis Stress Analysis

Pin Design

RF = 1.09


Team Maverick: Undercarriage beam

Behjat Ansari, Lourens Blok, Aewis Hii, Tom Hounsell,

Arjun Radhakrishnan and Beth Russell

Supported by

Design

• Symmetric cross sectional design.

• Ply-drops along the length and crosssection to increase structural efficiency.

• High strength carbon fibre is usedthroughout, with woven fabric used for all

±45° plies and unidirectional fibres in the0° and 90° directions.

Build

• Off-the-shelf mould to minimise overall costs.

• Hand lay-up of 54 plies over a male tool.

• Vacuum bagging and autoclave curing process.

• Post trimming of beam to final dimensions and fitbushings into hole cut-outs for pinned attachments.Layup trial over stainless

steel mould

Material test samples

Team Maverick has adopted an unconventional design approach. An upside downU-beam configuration was chosen to improve manufacturability, reduce costs andprevent eccentric loadings, but it requires a cut-out in the flange to apply thevertical load.

Critical buckling mode: 2.05 x ultimate load

Stress analysis Stability analysis

YZ

X

Impression of final lay-up on male mould

Stress in X-direction (MPa)

328

246

169

91.6

14.5

-62.5

-140

-217

-294

-371

-447

Deflection at limit load: 19 mm

Failure load: 1.0 x ultimate load

Stiffness per weight: 11.9 mm/kg

Test

• Material coupon testing carried out to derive materialproperties.

• Full scale test planned to assess final beamperformance.

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

Front cover photo credits:Jamie Hartley (top left), Yoho Media (top right and bottom left), Logan Wang (bottom right)

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