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On Prepreg Properties and Manufacturability Researcher: Dominic Bloom
Supervisors: Prof. Kevin Potter and Dr. Carwyn Ward
Stage 2: all materials laid up by professional laminators on a series of representative, doubly curved geometries. • Ramp angles range from 20° to 70° • Significant difference between
materials in time taken to complete each layup (up to 50%)
This work examines the role of material selection on the hand layup process. It attempts to identify the key aspects of a material which contribute to the ease or difficulty of manufacturing representative parts with relatively complex geometry. Initial results suggest that in addition to shear stiffness, flexural rigidity and tack are significant in determining the time taken to lay up a part and that this time may be predicted through a knowledge of these properties.
Stage 1: standard tests performed on 5 different prepregs to quantify relevant properties
ASTM D1388 (Flexural rigidity) ASTM D3167 Floating roller peel (tack) Bias-extension test (shear stiffness)
Stage 3: analysis Particle Swarm Optimisation suggests that including normalised tack and flexural rigidity terms improves the correlation coefficient (z-axis)
(Shear energy*Normalised flexural
rigidity)/ Normalised peel force [] x 104
Graphs show improvement in correlation when additional terms are included and overly challenging moulds are left out
Future work: • Identify suitable form of equation to
relate properties to time • Examine the role of downwards
pressure on lamination • Investigate further properties such as
spring-back
Material Resin Fibre Weave
CF1 (1) MTM49 Carbon 2x1 T
CF2 (2) 977-2A Carbon 2x2 T
CF3 (3) MTM44 Carbon 2x2 T
GF (4) 913 Glass 8 HS
CF4 (5) 913 Carbon Plain
+ Difficulty
prepreg
Aluminium plate
41.5°
prepreg Bending length
Smooth surface
weight
Peel force term (α)
Fle
xu
ral rig
idity te
rm (β
)
1-R
2
Time = Shear energy + α*peel force + β*Flex. Rigidity
Fixed datum constrains shear pattern
Theme: Complex Geometries
Composite design and manufacturing for successful product development Researcher: Dr Anna Chatzimichali
Supervisor: Prof. Kevin Potter
The composite sector is striving to cover current demand for sophisticated products in high volumes, while the composites supply chain is struggling to reach increased production rates. This work is focused on the interface between composite design and manufacturing, aiming to increase our understanding in effective composite product development processes.
The Challenge What is the key for increased production capacity and successful production ramp-up?
The Research Question How industrial teams consider manufacturing decisions during the early phases of composite product development?
Design & Development
Manufacturing Production Ramp-up
The Research Method Qualitative – Mixed method approach – Grounded theory
A series of semi-structured interviews with a number of industrial experts which target at gaining knowledge of the current practices of the UK composite industry
Alternative manufacturing techniques
Definition of specifications and requirements
Design iterations
Right-first-time manufacturing
Learning-by-doing
“Infinite material-process combinations”
Manufacturing capacity
“There are always things you don’t know, you don’t know”
Reliable and repeatable processes
Design capability
“Black-aluminium”
“The client asked for an impossible design”
Current Results Individual transcripts from the 1st round interviews (N=7, tape recorded: 14hours) are reviewed for key statements and emerging themes
Initial analysis indicates that certain trends emerge according to the position in the supply chain and the individual culture for each industrial sector
Theme: Complex Geometries
Using hand layup techniques to inform the design
of novel automated manufacturing processes Researcher: Michael Elkington
Supervisors: Prof. Kevin Potter and Dr. Carwyn Ward
A large number of complex composite products are made by hand from sheets of pre impregnated woven material. It is a complex process with many variables which can all have a huge influence on the quality, strength and cost of the finished product. However, it has not yet been studied in detail. Here, the techniques and methods used by laminators during lamination will be investigated to form a Knowledge Based System (KBS). This system can be taken forward to inform and inspire the design and operation of novel automated manufacturing processes.
Example: Comparing two layups: Differences in technique can be observed while forming the same
shape via different paths. Fig. 1 highlights one of many details which help determine the appropriate technique.
Red line = Start point, Blue = Regular cloth, Green = Sheared Cloth, = Layup direction (Away from starting point) Dotted Purple = Sheared tow angle, Solid Purple = Unsheared tow angle.
The required techniques can be identified for any feature, considering the shear angle, local topology and other factors. This knowledge will be used to inform the design of novel automated processes.
Predict deformation pattern with kinematic modeller.
Detailed layup study: 19 Unique tasks were completed by 6 Laminators and then analysed to record
both the time taken and the techniques used to form each section of the plies. An example is seen below in Fig 1.
93 % of areas with this type of shear were formed by
applying out of plane pressure and using tool shape to create shear.
70% of areas with this type of shear were completed
by applying tension to the cloth directly
Fibres rotate towards free edge. Fibres rotate away from free edge.
‘Preshearing ‘ The process of shearing the cloth dominates the hand layup process. It is proposed to semi automate
the layup process to apply sufficient shear prior to layup, as described below:
Apply shear prior to tool contact. Show here being achieved manually, but open to automation
Ply fits easily into tool allowing rapid layup.
60% reduction in on-tool layup time.
70% reduction in grasping
techniques use.
Key findings: • Different layup paths require different shear ‘types’, which can require specific techniques.
• Large corner radii do not necessarily mean ‘easier’ or faster layup. • Some tool shapes take significantly longer than others, despite having similar shear angles
Fig 1 – Schematic of two layup paths over the same tool, and examples of frequently used techniques.
Theme: Complex Geometries
1. Automation of activities 1-3
2. Studies into man-machine interactions for the lay-up of complex geometries
3. Factory processes not commonly researched, such as tool inspection
4. Developing a predictive capability, costing, and processing techniques
Forming routes (tool loading only)
Automated processIntermediate processMechanised processManual process
Classic (mylar aid)
Projection aids
PlyMatch aids
DfM enabled drape
VFP drape (UoB)
Vacuum
HDF, single film
HDF, double film
Stamping (inc. R.tool)
Hot oven
Hylid/rubber
Liquids (Q.Step)
Z-pin/tuft/stitching
Compression moulding
ATL/AFP std processes
F.Forge/Accudyne eg
Filament winding
2D/3D braid/stitching
Tube rolling
Pultrusion etc
Spray/DCFP/Ford
Operator tacit knowledge
Open/closed tooling
Varients (example Brötje, Dieffenbacher, Accudyne)
AFP TP process EADS
AFP process UoB
Ply/preform pick & place- Gantries (Shorts)- Robotics (P. Aerotec)
Pad printing
Embroidery (Tajima)
Patch preforming
Surface spray/binding
Printing/layer add-in
2D stack preforming
Active tooling (UoB)
3D preforms/ing
Local modifications- Chamfer/drape- Weaving- Networks (cut/fill)- Functionality inserts
Multi-step forming
Cure preparation
Automation set-up
Forming routes (tool loading only)
Automated processIntermediate processMechanised processManual process
Classic (mylar aid)
Projection aids
PlyMatch aids
DfM enabled drape
VFP drape (UoB)
Vacuum
HDF, single film
HDF, double film
Stamping (inc. R.tool)
Hot oven
Hylid/rubber
Liquids (Q.Step)
Z-pin/tuft/stitching
Compression moulding
ATL/AFP std processes
F.Forge/Accudyne eg
Filament winding
2D/3D braid/stitching
Tube rolling
Pultrusion etc
Spray/DCFP/Ford
Operator tacit knowledge
Open/closed tooling
Varients (example Brötje, Dieffenbacher, Accudyne)
AFP TP process EADS
AFP process UoB
Ply/preform pick & place- Gantries (Shorts)- Robotics (P. Aerotec)
Pad printing
Embroidery (Tajima)
Patch preforming
Surface spray/binding
Printing/layer add-in
2D stack preforming
Active tooling (UoB)
3D preforms/ing
Local modifications- Chamfer/drape- Weaving- Networks (cut/fill)- Functionality inserts
Multi-step forming
Cure preparation
Automation set-up
Current automated manufacturing processes, such as Automated Tape Laying (ATL) and Fibre Placement (AFP), have been relatively successful when applied to the manufacture of large monolithic parts of limited complexity. But as part geometry becomes more complex, rate and quality of lay-up is severely impacted on. This has meant those techniques are unsuitable without significant development and process adaption. As a result, today, for many composite components only manual lay-up can offer sufficient process flexibility to enable successful manufacturing. The challenge then is to develop low cost, highly productive processes that may work or compete with manual processes for complex geometries in the current work environment, at a significantly reduced cost, and using current materials (i.e. pre-impregnated broad-goods).
IMMEDIATE FURTHER WORK ONGOING PROGRAMME CONCLUSIONS
1. Exploit the backing film removal concept to a final demonstrator in order to explore feasibility trials
2. Continue the manual-aid research, including novel use of lay-up tools
3. Explore man-machine interactions
4. Explore quality/costs interactions
1. Programme works are ongoing, and some areas are progressing well for novel outputs, for example the demonstration of an automated backing film removal system (paper submitted to SAMPE SETEC-13 on this area)
2. For the target geometries, manufacturing on a man-machine interaction level, rather than a fully automated system that replaces the operator, appears the most appropriate route for successful application of the research themes
Novel Approaches to the Manufacture of Complex Geometries from Broadgoods
Researcher: Carwyn Ward Supervisor: Prof. Kevin Potter
ONGOING PROGRAMME ABSTRACT
Complex panel manufacture is a batch process, and is operated as a complex set of value stream activities with some interactions (Figure 1). To date a significant proportion of the R&D effort has concentrated on the ply deposition stage, with increasing activity in pick and place robotic-based research (Figure 2 for example), even though a myriad of techniques are available (Figure 3). This concentration on lay-up perhaps misjudges where automation can best return a positive impact, and does not consider common process bottlenecks. Many works also appear to target full replacement of the lay-up operator, despite the fact that man-machine interactions as a combined knowledge-base system may be the optimum process.
COMPLEX PANEL COMPOSITE MANUFACTURE
Materials in Ply cutting & kitting
De-moulding
Cure
Lay-up
NDT inspection
Fix on any sub-
components
Machining
Paint
Paperwork assembled Dispatch out
Finish, assemble metallic details
Inspection
Storage/defrost
Tool preparation Inspect & Report
Design and DfM data Product/part
Figure 1. The general value stream in composites manufacturing.
Figure 3. Lay-up opportunities.
Figure 2. Simple robotic deposition research, exploring tape and preform deposition quality.
End
0 V, m/s Distance, m Start
Max.
Measurement zone
Force, N
Velocity, m/s Glass Tool
Material
Felt
Table
RESEARCH ACTIVITIES
1. Design for Rate in Manufacture:
2. Protective Film Removal:
3. End Effector Development: 4. Robotics:
An autonomous or manual use system, to improve on protective film removal in a reliable, defect free, and controlled manner.
Figure 7. Protective film removal concept in action: paper (left), polymer (right).
Fig 4. BAC 5317 Rev F.
0° 50mm
Achieved as Figure 6 and through defeating the resin tack by temperature manipulation, Figure 7. Figure 6. Concept schematic.
Air in, 4-7 bar
Vacuum gripper
Prepreg
Venturi
Blower, edge target
Figure 10. RMR set-up.
Exploitation of the Relative Motion Robotic (RMR) rig Figure 10, for automation tasks including:
(http://www.schmalz.com/?lng=en) Figure 8. Rigid assembly.
Figure 9. Flexible assembly in pick and place and lay-up.
Schmalz vacuum cups have been selected for flexibility and working compatibility. Work explores use for pick, place, and drape activities; in rigid body (Figure 8) and/or flexible (Figure 9) systems. Novel lay-up aids, such as pad printing and assistive techniques are in development.
Exploring design changes required of a complex geometry, to enable rate, quality, reduced cost, and automated manufacture. Uses typical design flexibility (Figures 4 and 5) and other novel opportunities, with drape simulation and factory cost estimation.
Chamfer bevelled, taper from D (12.7-50.8mm) to C (0-3.81mm)
Flat: ±1.27mm Radius round off: 12.7mm to 50.8mm
B detail
±3° tol.
Sharp: 0-1.27mm
A
A
B Section A-A
D C
0°
In-plane shear result (using Virtual Fabric Placement)
Fig 5. Design modification of a U-Shaped tool.
R. 12.7mm R. 50.8mm
R. 50.8mm taper to 3.81mm R. 1.27mm round the base
20° Ramp
15°
2m D
0°
300mm
0°
0°
0°
0°
0° 50mm
50mm
50mm
50mm
(No
t to
Sca
le)
Air out, recovered at pressure and cooled to 0°C (+2°C). Air re-directed to blower
Theme: Complex Geometries
Advanced Composites Manufacture: Cost Modelling Researcher: David Ayre
Supervisor: Andrew Mills
Introduction Manufacturing routes for advanced composites include compression moulding, autoclave curing, resin transfer moulding, vacuum infusion (SCRIMP, RIFT), pultrusion, filament winding. In addition there is choice of reinforcing material- glass, aramid, carbon – material ply geometry – UD, woven, NCF – and whether prepreg or dry fabric. This choice of material and manufacturing process can result in a difference to manufacturing cost and composite part performance. To date there have been virtually no publically available studies or models of manufacturing cost to allow a useful comparison of both established and emerging materials and manufacturing technologies. This study aims to build a database of case studies of composite manufacturing techniques, best practices and comparative costs which could be used to benchmark emerging novel technologies and provide alternative manufacturing options to the composites industry – a composite manufacturing decision support tool.
Background Previously studies have focussed on specific niche markets. Figures 1 and 2 below are extracted from an aerospace study, investigating the effect of process on cost, and an automotive study, investigating the effect of material on cost.
Figure 1 Aerospace application cost analysis Figure 2 Automotive application cost analysis
Current Research Plan
Case Studies
Manufacturing Processes
Materials
Best Practice
Design Requirements
Materials and Process Options with associated case studies , best practices and comparative costings
Discuss with Industrial Partners and University Partners current process, materials, costs and ‘best practice’ for advanced composites manufacture
Compile process, materials, costs
and ‘best practice’ databases Compile Case Studies database
based on Industry experiences Link Databases
Embed Databases into a ‘decision
support software tool’ to provide composite manufacture options for a given product
Future Research Validation of the decision support tool – using literature data, lab based data
and data from industry where available Incorporation of new and emerging composites manufacturing technologies
NRC Aerospace (2006) –Fabrication of composite rib chords (Resin Transfer Moulding)
NRC Aerospace (2006) –Alignment of rib chord prior to bonding
Quickstep™ Process – Deakin University, Australia
Aviation News (2010) – Spirit Aerosystems cure of an A350 all carbon fibre fuselage panel
Aviation News (2011) – Premium Aerotec construct the all composite forward fuselage for the A350 XWB
Flight International Image – schematic illustrating extensive use of composite materials in the A350 XWB
Composites Technology 2012 - Teijin (Tokyo, Japan) 60-second thermoplastic composite press-forming process
to mould a passenger cell on a vehicle
McLaren MP4-12c
Vientek wind turbine blade manufactured using resin infusion technology
LM Glasfiber – Composite wind blade constructed in two halves and then bonded together using epoxy adhesive
Huntsman Advanced Materials (2012) –Araldite RTM system used for the production of the first carbon fibre
chassis on the Lamborghini Aventador LP700-4
Theme: Structural Joints
Experimental Investigation on Novel Hybrid Composite-Metal Joints Researchers: Vincenzo Di Giandomenico, Adam Joesbury, Marta Portela Millán
Supervisors: Andrew Mills, David Ayre, Giuseppe Dell’Anno
Result of double-lap shear loading
Previous study on stainless steel plates
Pinned stainless steel plate embedded in carbon fibre/epoxy composite laminate
• Regular array of 35 pins formed on both sides of plate
• Plate embedded into a quasi-isotropic lay-up of M21/T700 prepreg by ultrasonication
• Laminate cured in an autoclave
Pins encapsulated in CFRPMetal plate with pins
attached by CMT-Pin
welding process
5mm
5mm
Load bearing capabilities All inserts fail by catastrophic
sudden failure Failure initiates at the edges of
the overlap Large diameter CMT pins provide
the highest failure loads CMT pins are in general more
effective than EBM ones CMT pins provide higher energy
absorption by maintaining their integrity during fracture and failing by pull-out and composite delamination
EBM pins always fail in shear at
the pin base at lower loads than CMT ones
Ball-head on pins does not
provide any load capability benefit to the joint in this configuration
On-going work
Identification of optimal pin density and selective pin placement Design of joint including a selection of pin shapes Use of Digital Image Correlation system and High Frequency cameras
for the analysis of joint strain and failure mechanisms Identification of methods for promoting progressive failure
Partially failed joint Test halted at a joint strain of ~1%
Stainless steel-composite joint after full failure
Titanium metal joint: Samples manufacturing and testing
• Ti-6Al-4V alloy as metallic substrate
• Toray T1000 UD carbon fibre / MTM49 resin as embedding laminate
• Layups
-{[45,0,90,-45,0,90,0]s}s
-{[0,90]7,0}s
• Pins inserted by Ultrasonication
• Joint tested in tension
Spike pin Ball-head pin Tilted pin
Ø 0.8mm and Ø 1.2mm Ø 0.8mm ball-head Ø 1.2mm
Ø 0.8mm tilted by 30°
Objective To achieve efficient bonding between metals and polymer composites, as a feasible, beneficial and practical alternative to mechanical fastening and adhesive bonding.
Background Fibre reinforced polymer composites and metals are widely used structural materials. They are characterised by significantly different properties, manufacturing processes, and in-service behaviour; nevertheless, they are frequently used together within a single load carrying structure. This work investigates some novel methods for joining composites to metals.
Pins manufacturing CMT appears more cost-
effective Tilted configuration impossible
to produce by CMT technique Geometric features on pins are
more controllable and reproducible by EBM than by CMT
Manufacturing methods for pinned titanium alloy plates
Electron Beam Melting (EBM)
• Piece geometry defined by computer model and generated by metal powder melted by electron beam
• Pre-heating of powder reduces residual stresses
• Environment under vacuum allows use of reactive materials (Titanium alloy)
• Surface finish of the part is relatively rough
Cold Metal Transfer (CMT)
• Arc welding process by Fronius • A wire is welded and pins are
‘formed’ by high current pulse • Different shapes, heights and
angles possible • Less distortion to the parent
material due to low thermal input
• Titanium alloy pins to be formed in inert atmosphere to avoid reaction with Oxygen/Nitrogen/ Hydrogen
Titanium-composite joint after failure
Pinned joint transfers the same maximum load as the control joint
The energy absorbed by the pinned joint over failure is much larger than the control
Structural failure is delayed by gradual damage progression
Theme: Structural Joints
New Approaches to Composite Metal Joining Researcher: Adam Joesbury
Supervisors: Dr David Ayre and Dr Paul Colegrove
Strain measured across joining interface
30% of joint ultimate failure strain
60% of joint ultimate failure strain
Completely failed joint
Inspection of partial failure tests confirm that pins carry load by crossectional shear after adhesive disbond
Stainless steel 304L anchored metallic ‘z-pins’ manufactured
by Fronius CMT-Pin welding additive manufacturing process
Weld-stitched dissimilar material interleaves
Metallic ‘z-pin’ micromechanical fasteners inserted into uncured Hexply M21T700 prepreg by use of ultrasonic hammer and complete joint cured in
autoclave
Resistance spot weld-stitching through interleaves of stainless steel 304L sheet and plys of Hexcel G1157. In co-operation with Lessius University College, Belgium
Resin infusion of HexFlow RTM6 epoxy
Outline of investigation
The work presented here investigated alternative methods of forming mechanically reinforced adhesive structural joints between Carbon Fibre Reinforced Plastic (CFRP) and metals. This has been achieved by exploring new joining concepts and meeting the challenge of manufacturing not only proof-of-concept prototype joints but also specimens that can be mechanically tested to understand how the concept joints respond to loading, and furthermore to characterise the failure mechanisms that occur.
Anchored metallic ‘z-pin’ micromechanical fasteners
Conclusion
Investigations have shown that, when compared to adhesive-only joining, the use of these novel mechanical fastening elements result in greater strain at both initial and ultimate failure and also an overall fail-safe behaviour is achieved. When considering manufacturing processes: by eliminating the need for post-cure laminate processing for the purpose of fastener installation, while still achieving a desirable fail-safe behaviour by employing novel mechanical fastening elements prior to cure, a potential cost saving is enabled. Future research
This line of investigation will be concluded by further mechanical testing of Anchored Metallic ‘z-pin’ Micromechanical Fastened Joints, the geometry of which has been chosen as a result of a geometry sensitively study performed using associated finite element modelling activates that were conducted by Francesco Bianchi as part of the Bridging the Divide research project.
The work presented here was funded through the Cranfield University IMRC
Back ground
This work formed part of the Cranfield University IMRC Bridging the Divide research project, which was organised to consist of several work packages including of a mixture of prototype definition and investigation, collaborative work, and detailed individual investigation. The collaborating partners of the Bridging the Divide project were: Cranfield University, BAE Systems, EADS Innovation Works, and Airbus Operations GmbH. Work within Cranfield University was shared between the School of Applied Science’s Composite Centre and Welding Engineering and Laser Processing Centre departments, and the School of Engineering’s Department of Aerospace Engineering.
35mm
12mm
Theme: Structural Joints
Hybridised Composites by Tufting Diego Marcelo Lombetti
Supervisor: Dr G Dell’Anno and Prof. I Partridge
1.6 m
Steel mesh wire Ø 0.15mm
E-glass Aramid tuft
Bottom view
Tufts (fibrous or metallic)
Micro-fasteners (metal pins)
Top view
Multi-material substrate Composite laminate
Metallic layer(s)
Metallic attachment
Quarter of a full scale business jet composite tail-cone being tufted with aramid thread (part of the ADVITAC FP7 EU project)
Development of conceptual demonstrator
Objective Developing the technology to manufacture innovative Multi-material and Multi-architecture preforms
Methodology Explore tufting as a possible route to integrate metal parts into composite substrates
Expected Outcome
Facilitating the joining of dissimilar materials
Improving the out-of-plane strength of the assembly
Alteration of electrical conductivity of the assembly
Automated tufting of complex 3D geometries
Upgrading tufting routines and controls
Manufacturing of multi-material substrate
• Integration of metal layers into composite layup
• Tufting with metal/fibrous threads • Mechanical properties assessment
(CAI and ballistic tests)
Effect of tufts on electrical conductivity
Quantitative assessment of through-thickness conductivity and response of tufted panels to lightning strike exposure
Engineered thread
Designing an engineered fibrous/metal hybrid thread
Co-weaving metal tows
Investigation on alternative metallic, co-woven inserts (with Manchester University)
0
500
1000
1500
2000
2500
0 1 2 3 4 5 6
Stress
[MPa
]
Strain [%]
Tensile Test
Glass Carbon Aramid Stainless Steel
Example of metal insert integrated into carbon fibre composite component
Courtesy of McLaren Racing
Carbon fibre/epoxy composite tufted with glass thread after lightning strike test
Theme: Structural Joints
Development & Modelling of Multi-axial Textile Preforms
Researcher: Khayale Jan Supervisor: Dr. Prasad Potluri
Research Objectives Development of multi-axial multi-layer 3D-braided preforms locked by binder yarns to enhance out of plain properties. Development of dry fibre preforms in variety of shapes and forms with flexible dimensional capability. Designing a novel multi-axial textile machine which is based on Cartesian braiding process.
Summary The study emphasises the potential of 3D braiding to place the yarn in position at different angles producing variety of fibre architecture in the desired shapes and forms of the braided structures.
Future Work Samples so produced will be consolidated, tested and
analysed. Modelling to predict mechanical properties of the
braided architecture.
I nt ro d u c t i o n Textile preforming in one step, adaptable for various shapes and sizes with better mechanical properties is still a burning issue in the realm of high performance applications of 3D-textile composites. Weaving, in spite of being capable of producing wider width panels for composites, has certain limitations towards near-net shape preforming. Braiding technique is one of the possible solutions to the question though being impeded by limited cross-section and length of braid element.
Aim: The braided textile preforms exhibit poor out of plain properties, and low stiffness and strength. In order to
improve these properties, implementation of through thickness reinforcement is needed. This research focuses on design and development of a process which can fulfil these requirements.
Methodology/ Approach Cartesian principle of braiding, especially the four-
step row and column braiding, is investigated and comprehended.
Two-step braiding is also incorporated to introduce locking yarns.
The proposed concepts have been drawn for the development of novel braiding machine.
Proposed Concepts A circular row & column braiding machine capable to
produce tubular braid structures has been proposed. A flat bed row & column braiding machine with continuous
supply of yarn has been proposed to produce longer length braiding elements.
Both of the above machines are capable to employ braiding, axial and locking yarns.
Progress A fully automated prototype machine capable of
producing variety of architectures is under development to validate the concept.
3D-Solid Braid Machine Bed
2D-Braiding Machine
2D Over Mandrel Braided Structure
3D-Braid Architecture
CAD models of Braid Architectures
4-Step braiding Scheme 2-Step braiding Cycle 4-Step Cartesian Braiding Cycle
Novel 3D-Braiding Machine
Theme: Innovative Preforms
Automation for Dry Fibre Preforming Researcher: Dhaval Jetavat Supervisor: Prasad Potluri
9 Axis winding machine
Fibre Placement System with a minimum of 4 Degrees of Freedom
Able to wind around a curved part through the use of a third rotating axis
Able to accept a part whose geometry changes along its‘ length
Package design Designing package and fibre path in order to increase process efficiency and product parameters Mandrel support design along with process cycle
Aerospace composites are traditionally manufactured using expensive prepreg systems where individual prepreg plies are cut to shape, stacked in preferred orientations and subsequently cured in autoclaves. Another route to manufacture large composite parts is Automated tape laying and Fibre placement. These are essentially machine tools to deposit thin layers of prepreg tape precisely on a mould surface. These manufacturing routes are hugely expensive and less productive. In recent years, dry fibre preforms in conjunction with liquid infusion techniques (vacuum infusion, Resin Transfer Moulding) are becoming popular as a means of improving productivity and reducing process costs. This research is focused on Automation combined with textile technology which can provide low cost solution to manufacture complex shape composite part.
Introduction
Robotic Tow placement
To produce a perform with a large number of layers in 0o, 90o and ±θo directions
To produce a preform with single or double curvatures
To incorporate through thickness reinforcement
Textile Technology
Weaving, braiding and stitch-bonding are three preferred methods
Modification to existing techniques to produce various fibre orientation
Tool design Novel robotic head for tufting and lay-up Flexible approach in tool design to provide required fibre configuration on complex shape structures
Research Objectives
Combining textile technology with robotic automation in order to achieve cost effective solution for near net shape preforming To develop novel concepts, processes and machines for complex near-net fibre preforms incorporating multifunctional, multi-materials Developing machine assembly and tool in order to reduce fibre damage and increase process efficiency
Textile Technology
Automation
Purpose built technologies
Theme: Innovative Preforms
Metallised Carbon Fibre Preforming for Composites
Researcher: Vivek Koncherry Supervisors: Dr Prasad Potluri and Dr Anura Fernando
Bending of the MCF tow under the influence of an array of Neodymium Iron Boron disc magnets: Experiment and FEA
1. Metal Powder Percentage
2. Space Between Print Line
3. Width of Each Print Line
Carbon fibre composites have a unique place in the automotive, aerospace and wind energy sectors due their high strength to weight ratio. The composite manufacturers engaged in these areas, are on the constant lookout for new materials and technologies to increase the manufacturing efficiency and economies of production.
In the recent times Direct carbon fibre preforming (DCFP) has been developed in order to produce carbon fibre parts more efficiently and at low cost.
Research Aims To create a new composite preforming material for the DCFP
process Develop a prototype machine to manufacture the new
material Scientific characterisation of the new material
Conclusion and Future Work Various iterations of machine designs that were studied have shown that the current design of the prototype MCF production machine is an excellent method for creating MCF tows. The studies have shown that, to achieve optimum levels of the bending stiffness and magnetic pull force expected from the MCF tow, it is possible to systematically engineer the tow, so that for a particular magnetic field strength, it is possible to determine the optimum mould wall thickness, mould curvature, print line width, print line frequency and quantity of powder in the lines.
Prototype machine and MCF material developed at the University of Manchester
Magnetic pull force on the MCF tow: Experimental results and the validation using Finite Element Analysis (FEA)
The theoretical bending deflection results (2.22 mm) predicted by the Finite Element Model was validated using the observed experimental results (2.17 mm).
Spare wheel well demonstrator made for Bentley Mulsanne using MCF tow
The new composite preforming material, which is a metallised carbon fibre (MCF) is placed on to the moulding tool in the form of chopped carbon tow. The material is held on the 3D mould surface using an electromagnetic field. This new technology is an alternative to the currently used suction based DCFP process.
Characterisation of the MCF tow by varying the process parameters in terms of magnetic pull force and air gap:
0
1
2
3
4
1 2 3 4 5 6 7 8
Forc
e (
cN)
Air Gap (mm)
Experimental
Ansys Model
Theme: Innovative Preforms
Multi-scale Damage Tolerance in Textile Composites Researcher: Erdem Selver
Supervisor: Dr. Prasad Potluri
Introduction
Experimental Works In this research, hybrid yarns which contain thermoplastic fibres (polypropylene) and glass fibres (S and E) were manufactured. Then, these hybrid yarns were used to make composite samples in order to increase toughening properties of these structures. A robotic tow placement machine was used to create the preform. Also, a self-healing mechanism was created
by hot-pressing the low-velocity impacted specimens.
Conclusions and Future Works Adding polypropylene fibres to composite system helped for improving plastic deformation and toughening mechanism. A novel self-healing mechanism was created by embedding
polypropylene fibres on the host of S-glass/Epoxy system. Impacted areas were recovered and compression force values increased after the healing process. For future works, through the thickness reinforcement will be made in order to improve damage tolerance behaviour using tufting or stitching method with hybrid yarns. Also, some thermoplastic experiments will be conducted with those hybrid yarns.
Figure 1. (A) Commingling (B) core-wrapping Figure 2. Yarn placement Figure 3. S-glass/PP-Epoxy
Commingling nozzle
Figure 4. Hot pressing of hybrid composites
Figure 5. Compression after impact behaviour of samples
Impacted
After healed
Figure 7. C-Scan images before and after the healing
Figure 8. Load-displacement history Figure 9. Impacted sample after healing
Compression After Impact Investigation Self-Healing Investigation
Results and Discussion
A B
0.0 0.5 1.00
5000
10000
15000
20000
25000
30000
Lo
ad
(N
)
Displacement (mm)
Non-impacted
Impacted
Healed
CAI results showed that there were slight increases in residual strength of the some hybrid samples due to bridging effect of polypropylene fibres which remained both side of the layers.
0 10 20 30 40 500
50
100
150
200
250
CA
I S
trength
(M
Pa)
Impact Energy (J)
S-glass-PP/epoxy (commingled)
S-glass-PP/epoxy (co-wrapped)
S-glass/epoxy
0 10 20 30 40 500
50
100
150
200
250
300
CA
I S
tre
ng
th (
MP
a)
Impact Energy (J)
E-glass/Epoxy
% 15 PP addition
% 15 PP addition-woven
%21 PP addition
%28 PP addition
C-Scan tests indicated that most of the damaged regions were recovered after the
healing process.
Failing force value is the highest at non-impacted sample and it decreased almost 50 % after the impact event. However, force values increased again due to recovery of the damaged regions after the healing process
Figure 6. Images after CAI test
S-glass-Epoxy S-glass/PP-Epoxy
PP PP
E-glass/PP-Epoxy
Core yarns
Wrapping yarn
Core-wrapped yarns
Rotating base
This work aims to understand the damage tolerance mechanism in textile composites at fibre, yarn and composite laminate scales. Based on this, novel fibre architecture using commingling or core-wrapping methods were developed in order to improve damage tolerance behaviour at final composite structure.
Theme: Innovative Preforms
Design and Development of 3-D Interlocked Weaving Process Researcher: Sandeep Sharma Supervisor: Dr. Prasad Potluri
Introduction to Manufacturing Technology of Woven Textile Preforms
The process of weaving can be divided into two categories depending upon the type of fabric produced i.e. 2-D and 3-D weaving
processes. The 2-D weaving process interlaces two sets of orthogonal yarns known as warp, laid in 0º and weft at 90º direction to
produce a fabric. The 2-D weaving system generally operates on the principle of one shed opening and one pick insertion in one
weaving cycle. These fabrics are generally termed as single layer fabrics, however thicker fabrics up to certain thickness can be
woven by employing multilayer weaving technique as indicated in the figure 1.The 3-D weaving technology is a variant of 2-D
weaving process where three orthogonal sets of yarns are interlaced in x, y and z directions. The process is carried out on
specially designed 3-D weaving machines. Figure 2, illustrates the basic concept of 3-D weaving. The newly designed 3-D weaving
system operates on the principle of multi-weft insertion in a single weaving cycle as shown in figure 3. 3-D weaving machine
based on multi weft insertion is shown in fig 4.
.
Single Layer Fabric
Multi-layer Fabric
Figure: 1 Two Dimensional Weaving Process Fig: 2 3-D Weaving process
Why 3-D Woven Textile Preforms
Near-Net Shaped preforms can be fabricated with ease, thus
reducing part count.
No layering of fabrics needed to achieve required part
thickness.
Handling of pre-shaped dry preforms is far easier than single
layer fabrics.
Near-Net shape weaving by using warp and weft ply drops.
Various 3-D Weave Architectures
Various 3-D Near-Net Shapes
Fig: 3 Multi-Weft Insertion system
3-D Regular Orthogonal Weave 3-D Regular Angle Interlock Weave
Layer-to-Layer Angle Interlock Weave Layer-to-Layer Orthogonal Weave
Ply Cut Point
Weft Yarn
1
2
3
4
Fig: 4 3-D Weaving Machine (University of Manchester)
Theme: Innovative Preforms
Tool Design A low-weight lay-up and tufting tool was manufactured in substitution of a previous tool in order to minimize the inertia of the robot and increase the speed of lay-up. For the pins holding support, on the first tests were used PVC plies and after those tests were satisfactory and aluminium tool was designed and manufactured.
Robotic Dry Fibre Placement of 3D Preforms Researcher: Alvaro Silva-Caballero
Supervisor: Dr. Prasad Potluri
Robotic Preforming Concept Robotic preforming aims to overcome the limitations of conventional textile techniques by achieving the following objectives; • To produce preforms with any arbitrary geometry lengthwise and width-wise, • To produce a perform with a large number of layers in 0o, 90o and ±θo directions, • To produce a preform with single or double curvatures, • To produce taper in thickness in any direction, and • To incorporate through thickness reinforcement using the tufting technique.
Conclusions and Future Works The present research is focused in the development and optimization of a manufacturing technique for building near net shape preforms. The tooling must be improved and redesigned to overcome the limitations of the previous generation. New tools to extract the preform from the mould must be designed. A more efficient and accurate path planning algorithm must be implemented. Once the manufacturing process has gained certain degree of maturity, experimental work to determine the physical and mechanical properties of the preforms must be conducted.
Figure 1. Dry fibre placement concept. Figure 2. Robotic dry fibre placement. Figure 3. 45° fibre orientation.
Path Planning Algorithm Implementation Observations
A path planning with complete information algorithm, better known in the literature as the piano movers problem was implemented in order to determine the trajectory which the robot must follow to lay up the fibre onto the mould. In this algorithm the controller is fed with precise information about the obstacles, i.e. the position of the pins. As robot has full “knowledge” of its environment, the whole process of path planning is a one-time, off-line operation being therefore relatively easy to implement.
The pins located in the central part of the mould lead to gaps in between the tows and
the loops created when the yarn turn around the pins produce a bumpy surface. After the infusion process the finished part present holes in between the loops of the external layers.
In recent years, dry fibre preforms in conjunction with liquid infusion techniques (vacuum infusion, Resin Transfer Moulding) are becoming popular as a means of improving productivity and reducing process costs. Reinforcing fibres, in the form of yarn or roving, are arranged in the required shape of the component (preform) prior to infusion with a matrix material. In the robotic preforming concept, a preform is built by stacking several layers of dry fibre. Each layer is produced by placing side by side straight segments of fibre, each one, ideally parallel to the others. The operation is accomplished by a 4-DOF Cartesian robot programmed with a trajectory planning algorithm which generates the trajectories needed to lay up the fibre automatically.
Figure 5. Trajectories generated automatically.
Figure 6. Gaps in between the tows left by the pins.
Figure 7. Bumpy surface created by loops.
Figure 8. Holes in between the loops after the infusion process.
Introduction
Figure 4. 45° fibre orientation.
Theme: Innovative Preforms
Effect of specimen history on measured in-plane permeability of fabrics Researchers: Dr A Endruweit, Dr X Zeng
Supervisor: Prof AC Long
batch K1 / 10-10 m2 K2 / 10-10 m2 K1/K2
1 3.232 0.936 1.720 0.463 1.898 0.301
2 1.600 0.117 1.196 0.333 1.420 0.446
3 2.981 0.176 1.312 0.135 2.292 0.370
Principal permeability values, K1 and K2, and ratio, K1/K2, for different batches of a 2×2 twill weave fabric (S0 = 285 g/m2) at a given fibre volume fraction, Vf = 0.49
Motivation
For a 2 x 2 twill weave carbon fibre fabric, three different material batches with identical nominal properties but different history were found to show significantly different permeability values.
history K1 / 10-10 m2 K2 / 10-10 m2 K1 / K2
unsheared 0.513 0.102
( 20 %)
0.354 0.070
( 20 %)
1.457 0.179
( 12 %)
sheared, clamped
weft, max. 20
0.732 0.198
( 27 %)
0.490 0.050
( 10 %)
1.535 0.596
( 39 %)
sheared, clamped
weft, max. 40
0.864 0.041
( 5 %)
0.589 0.016
( 3 %)
1.468 0.098
( 7 %)
sheared, clamped
warp, max. 40
0.947 0.208
( 22 %)
0.652 0.038
( 6 %)
1.444 0.234
( 16 %)
Principal permeability values, K1 and K2, and ratio, K1/K2, for a 2×2 twill weave fabric (S0 = 660 g/m2) after undergoing different shear histories at a given fibre volume fraction, Vf = 0.56
Summary
The shear history of a fabric was found to have an effect on inter-yarn gap widths and in-plane permeability values, both of which increase with increasing maximum shear angle.
Operator-induced effects, in particular related to the specimen preparation, and effects of gravity and handling during storage and transport were identified as sources of changes in the fabric structure resulting in permeability variations. These may lead to uncontrollable resin flow during reinforcement impregnation and eventually result in defect formation.
Fabric Geometry Analysis
The effect of the material history was simulated by repeatedly shearing to given angles and shearing back to a 0/90
configuration.
Automated analysis of photographs of the fabric surface, acquired after completion of each shear cycle (i.e. sheared back to 0/90 configuration), allowed the yarn width to be measured in 2D projection.
Lateral yarn compression in fabric shear may result in a decrease in yarn width, i.e. increase in inter-yarn gap width
Permeability analysis
Measurement of the in-plane permeability of specimens with different shear history indicated that the permeability increases significantly with increasing maximum shear angle. The influence of the direction of shear is small.
Project background
The effect of fabric history on its permeability was studied in the framework of development of meso-scale flow and cure simulation techniques to predict manufacturing defects arising from material and process variability.
Effect of repeated shear on inter-yarn gap width, wg, in a 2×2 twill weave fabric (S0 = 660 g/m2)
from roll after shear up to 40
10 20
40
on
set
of
wri
nk
lin
g
Theme: Multi-scale Modelling
-5
-4
-3
-2
-1
0
0 10 20 30
ln(K
/ K
hex
)
l / r
Vf63
Vf66
Vf74
6
8
10
12
14
16
1 2 3 4 5 6 7 8 9 10
Ave
rage
dis
tan
ce (
µm
)
The angle at which the n-th neighbour is located is changing from a random distribution to a more uniform distribution (indicated by increased probabilities of specified directions)
Frank Gommer
Cav
ity
hei
ght
Glo
bal
fib
re v
olu
me
frac
tio
n
0.37 mm
0.28 mm
0.22 mm
Vf = 45 %
Vf = 60 %
Vf =74 %
2 mm
Increasing levels of compaction lead to change in fibre bundles shape. In addition, this leads to a change of the micro-structure (by filament re-arrangement)
Compaction of fibre bundles
It was observed that the distance between neighbouring filaments is decreasing with increasing compaction. The change is more pronounced at higher Vf when the possible bundle change is limited.
Changing micro-structure
Motivation
Aim
• Subsequent measurement of the geometry in every fabric layers after placement in a mould tool during lay-up.
• Prediction of the fabric architecture after compaction (mould closure).
• Estimating fibre bundle deformation based on micro-mechanical prediction of measured filament arrangements in fibre bundles.
Future work
Results • A novel automated image analysis technique for the accurate
detection of filament boundaries was developed which • Enables the systematic analysis of two-dimensional micrographs at
high magnification. • Resulting micro-structures can be reconstructed employing an
adapted algorithm to create random filament arrangements.
A system will be developed which automatically gathers information on the fabric distortion in real-time during the textile stacking process of composite manufacture. Each layer will be analysed automatically during the lay-up process for the degree of intrinsic misalignment such as varying waviness and handling-induced shearing, both of which affect the fibre angle.
When the mould is closed the fabric layers are compacted leading to additional local yarn deformations. The resulting three-dimensional geometric arrangement will be predicted employing a compaction model based on the measured fibre bundle variations. The fibre rearrangement mechanisms in single fibre bundles measured in the previous project will be used for estimation of the compaction behaviour.
Motivation Models employing periodic filament arrangements ignore the intrinsic variability present within fibre-bundles. Accurate quantification of the micro-structure enables the prediction of subsequent properties such as the resin flow at the micro-scale.
To exclude effects such as bundle nesting, single layer 12K carbon fibre epoxy composites were characterised systematically at different levels of compaction (different fibre volume fractions Vf).
Stochastic modelling of textile structures for resin flow analysis Supervisors: Prof. Andrew C. Long and Dr. Andreas Endruweit
Detection of manufacture induced variability Supervisors: Prof. Richard Brooks
Computational models were automatically generated for simulation of transverse resin flow through reconstructed ran-dom filament arrangements with varying length, l, to fila-ment ratios, r. Steady-state permeabilities, K, were found to be significantly smaller than periodic arrangements (Khex). Convergence of the values were found at a l/r ratio of approx. 30.
The orientation of fibres greatly influences the resulting properties of a composite component; aligning the fibres precisely in the loading direction yields optimal properties. For instance, a deviation of just 2.5° reduces the compressive strength by 10%.
Vf = 0.45 Vf = 0.60
Vf = 0.74
Vf hex = 0.91 5
4
3 2
1
n-th neighbour
Vf = 0.45 Vf = 0.60 Vf = 0.74
neighbour: 1
2
3
4
v / vmax
0.00
0.25
0.50
0.75
1.00
K / r2 = 1.56 x 10-5
K / r2 = 2.49 x 10-3
Consequence of variable in micro-structures
Vf = 0.45
Vf = 0.60
Vf = 0.74
Example edge detection of a carbon twill weave:
Project start: March 2013
Example of a multi-layered 12K carbon fibre epoxy composite. Histograms of angle distribution (reduced to 90° by employed symmetries) are shown for selected fibre bundle cross-sections:
0.016
0.012
0.008
0.004
0 90 80 70 60 50 40 30 20 10 0 N
orm
alis
ed f
req
uen
cy
A)
0.016
0.012
0.008
0.004
0 90 80 70 60 50 40 30 20 10 0 N
orm
alis
ed f
req
uen
cy
Degree
B)
0.016
0.012
0.008
0.004
0 90 80 70 60 50 40 30 20 10 0
C)
0.016
0.012
0.008
0.004
0 90 80 70 60 50 40 30 20 10 0
Degree
D)
A)
B)
C)
D)
Prediction of resulting mechanical properties after manufacture of a composite component.
Goal:
An
gle
(d
egre
e)
Inp
ut
An
alys
is
Edge
s
Geometric variabilities in composites
Theme: Multi-scale Modelling
Stochastic Simulation of the Cure of Advanced Composites Researcher: Tassos Mesogitis
Supervisors: Dr. Alex Skordos and Prof. Andy Long
Introduction
Aim: to develop a stochastic cure simulation methodology and to investigate the uncertainty/performance trade-off in curing
Methodology
Cure simulation model • Material sub-models with dependence on degree of
cure and temperature
Stochastic cure simulation input parameters • Cure kinetics uncertainty • Boundary conditions variability • Fibre misalignment
Stochastic simulation model • Monte Carlo simulation scheme (MCS) • Probabilistic Collocation Method (PCM)
Quantification cure kinetics uncertainty • Differential Scanning Calorimetry • Samples from four different batches
Stochastic variables • Initial degree of cure
• 11% variability • Activation energy
• 0.3 % variability • Reaction order
• 3.6 % variability
Results and discussion
Cure kinetics can introduce variability in process output parameters • Cure reaction rate/temperature overshoot can show significant variability
Both stochastic simulation schemes can capture variability propagation • MCS presents a computationally expensive and rich solution • PCM offers an efficient solution (less than 1.5 % of CPU cost) with comparable accuracy
Future work Quantification and modelling of cure temperature and surface heat transfer coefficient variations Quantification and modelling of fibre misalignment in Non-Crimp Fabrics (NCF)
Cure reaction rate vs time- cure simulation of neat epoxy resin
Evolution of reaction rate with temperature during dynamic cure for a commercial epoxy resin
Conclusions
Schematic representation of methodology
Monte Carlo Simulation scheme • Random sampling from distributions • Large number of deterministic runs
𝑯𝟏 = 𝒚
𝑯𝟐 = 𝒚𝟐 − 𝟏
Collocation points • Roots of the next higher
order orthogonal polynomial
Gaussian variables • Hermite polynomials
Probabilistic Collocation Method • Construct response surface for output parameters
• Set of orthogonal polynomials (polynomial chaos) • Run deterministic model at a set of collocation points
• Use response surface for statistical analysis (MCS)
Res
po
nse
P
DF
(A)
Input A
Actual model response
Response surface
Input A
Collocation points selection at high probability region 𝑯𝟐 = 𝒚𝟑 − 𝟑𝒚
Selection of collocation points • Regions of high probability • Small number of deterministic runs
Convergence of statistic s of maximum reaction rate- cure simulation of neat epoxy resin
Convergence of statistics of temperature overshoot- carbon fibre epoxy flat panel (24 mm thickness)
0
0.00005
0.0001
0.00015
0.0002
0.00025
0.0003
0.00035
0.0004
0.00045
0 2000 4000 6000 8000 10000
reac
tio
n r
ate
(1
/se
c)
time [sec]
0
0.0001
0.0002
0.0003
0.0004
0.0005
0.0006
0.0007
0.0008
80 130 180 230 280
reac
tio
n r
ate
[1
/se
c]
Temperature [ºC]
A1
A2
B1
B2
C1
C2
D1
D2
CURE MODEL
Histogram of temperature overshoot [ºC]- carbon fibre epoxy flat panel (24 mm thickness)
Maximum cure reaction rate • 8.5 % variability
Temperature overshoot Carbon fibre epoxy flat panel (24 mm thickness)
• 2 % variability
11.522.533.544.555.56
179
180
181
182
183
184
185
186
187
0 500 1000 1500 2000
stan
dar
d d
evia
tio
n o
f te
mp
era
ture
ove
rsh
oo
t
me
an o
f te
mp
era
ture
ove
rsh
oo
t [º
C]
Monte Carlo iterations
Monte Carlo-mean
Collocation-mean
Monte Carlo-sd
Collocation-sd
0
50
100
150
200
250
17
1
17
3
17
5
17
7
17
9
18
1
18
3
18
5
18
7
18
9
19
1
19
3
19
5
19
7
19
9
Monte Carlo
Collocation
0
0.000005
0.00001
0.000015
0.00002
0.000025
0.00003
0.000035
0.00004
0.00035
0.000355
0.00036
0.000365
0.00037
0.000375
0.00038
0.000385
0 500 1000 1500 2000
stan
dar
d d
evia
tio
n o
f m
axim
um
re
acti
on
rat
e [
1/s
ec]
me
an o
f m
axim
um
re
acti
on
rat
e
[1/s
ec]
Monte Carlo iterations
Monte Carlo-mean
Collocation-mean
Monte Carlo-sd
Collocation-sd
Experimental data
Quantification of input parameters uncertainty
Stochastic simulation model
Cure simulation model
Quantification of output parameters uncertainty
Theme: Multi-scale Modelling
Multi-scale thermal mechanical FE analysis for Shape distortion in composites manufacturing processes
Researcher: Xuesen Zeng, Platform fellow Supervisors: Dr. Richard Brooks and Prof. Andrew Long
Introduction This is a case study aiming to demonstrate a multi-physics multiscale modelling approach for composites manufacturing processes. Coefficient of thermal expansion is directly relevant to shape distortion during composites manufacturing.
Heat / Cure
Compaction Draping, tow placement, nesting
K – permeability tensor
RVE/Unit cell Component
Fluid dynamics Fibre architecture, Vf , periodic boundaries CFD: ANSYS, ABAQUS, etc
Fibre level
Flow Resin infusion
Porous media Geometry, fluid viscosity, vents/injection points, fill time PAM-RTM, LIMS
α – CTE β – cure shrinkage Stiffness
Thermal/chemical/mechanical Fibre architecture, fibre elasticity, resin cure kinetics and shrinkage, CTE General FE: ANSYS, ABAQUS, LS-DYNA
Thermal/chemical/mechanical Geometry, cure cycle, tool interaction SYSPLY, LUSAS, COMPRO
Mechanical Dry/viscous fabric, frictions, shear, compression General FE: ANSYS, ABAQUS, LS-DYNA
Stiffness Mechanical Geometry, tool interaction PAM-FORM, FibreSim, Patran/Laminate modeller
The study focuses on unit cell FE modelling to predict coefficients of thermal expansion (CTEs) for sheared fabric laminates. Shear, as a dominant deformation mode in textile composites forming, introduces higher degree of anisotropy in both elasticity and thermal expansion. The unit cell predictions are based on realistic fibre architecture and measured material properties of constituent fibre and resin. Under the multi-scale framework, the unit cell predictions are part of the essential input data for locally varied material definition in modelling structural component to predict shape distortion.
Unit cell model Geometric description of sheared fabric is realised in TexGen with consideration of yarn rotation as two elliptical cylinders crossover each other in an oblique angle, seen in Figure 1. The rotational angle is derived mathematically from the tangential contact between yarns.
Figure 1. Geometric modelling of sheared fabric. (a) Wire-mesh view of yarn crossing; (b) Intersection free crossover after yarn rotation; (c) plain weave unit cell after sheared in 16 degrees.
1. Li, S., C.V. Singh, and R. Talreja, A representative volume element based on translational symmetries for FE analysis of cracked laminates with two arrays of cracks. International Journal of Solids and Structures, 2009. 46(7–8): p. 1793-1804.
Compatible voxelised mesh and periodic boundary conditions[1] for sheared domain have been implemented in TexGen GUI.
FE analysis Thermal mechanical analysis is performed in ABAQUS as static perturbation with a temperature change 1oC. According to the periodic boundary condition set-up[1], CTEs are recovered directly from the strain tensor:
𝛼𝑥𝑥 = 𝜀𝑥 ; 𝛼𝑦𝑦 = 𝜀𝑦 ; 𝛼𝑧𝑧= 𝜀𝑧 ; 𝛼𝑥𝑦 = 𝛾𝑥𝑦 ; 𝛼𝑦𝑧 = 𝛾𝑦𝑧 ; 𝛼𝑥𝑧 = 𝛾𝑥𝑧
Results FE analysis takes the material data for fibre, matrix and weave geometry listed above. Tow properties are obtained from a unit cell FE model of UD composites in hexagonal fibre arrangement (Vf=65%).
Fibre properties E11 =235GPa, E22 = E33 =15GPa, v12 =0.3, v23 =0.3, G12=15, αL = -0.4x10-6/K, αT = 10x10-6/K
Matrix properties E = 3.5GPa at 20oC, E=2.7GPa at 100oC, v=0.4, α = 59.6x10-6/K cast 15min at 120oC α = 40x10-6/K after the full thermal cycle
Yarn width Yarn height Yarn in-plane
spacing
Laminate
thickness
1.76mm 0.16mm 2.03mm 2.4mm
Warp
Weft
Sample cut angle θ
a b c
Figure 2. Sample orientations and dimensions for measuring linear CTE in dilatometer.
Validation case Laminates are manufactured from plain weave fabric CF0504 and aerospace grade resin MTM46. Three 10-ply laminates are (1) un-sheared (Vf =47.5%), (2) shear in 16 degrees & (3) 20 degrees. CTE measurement[2] from dilatometer Netzsch DIL 402C from samples orientated at various angles as shown in Figure 2.
Experiment & Models CTE in warp (x10-
6/K)
Note
Uns-sheared - Experiment 2.12
Single layer with periodic
boundary condition (pbc)
3.20
Two layers with Weft free
edges, pbc in warp and
thickness direction
2.33
Ten layers with Weft and
thickness direction free
edges, pbc in warp (3 sets
of random nesting were
modelled)
2.16±0.01
Warp
Weft
Model CTE prediction in
warp (x10-6/K)
16o shear -
Experiment
2.63
16o shear – coupon
model, single ply
3.2
16o shear – coupon
model, 10 plies
2.70
CTE prediction
in 135o (x10-6/K)
20o shear -
Experiment
15.66
20o shear – coupon
model, single ply
22.0
20o shear – coupon
model, 10 plies
17.0
Conclusion FE model gives prediction close to the experimental data, when the boundary conditions are set to simulate coupon size. Nesting is an influential factor for CTEs. For true material representation, in-plane periodicity and nesting shall be considered.
2. JONES, IA, AC LONG, and W. RUIJTER, SA SMITHEMAN, QPV FONTANA, MG DAVES, S. LI." Recent Advances in Textile Composites: Proceedings of the 10th International Conference on Textile Composites. DEStech Publications, Inc, 2010.
Theme: Multi-scale Modelling
Contact: Donna Astill E: [email protected] T: +44 (0) 115 951 3658
