Joining of composites

WEMMA, TWI & BCS LectureSean COOPER MSc BSc(Hons) CEng CSci MIMMM MIET

Materials and Manufacturing Development Manager

Nov 8, 2017 - 19:00

1. Introduction – About me / About Tods Aerospace

2. What is a composite material ?

3. Composites joints – Introduction. Primary, secondary and non-structural.

4. Methods for thermoplastic and/or thermosetting polymer matrix Composites : Mechanical fastening, adhesive bonding, hybrid mechanical fastening/bonding, co-curing.

5. Methods used specifically for thermoplastic matrix composites : Induction welding, ultrasonic welding, resistance welding.

6. Tods Aerospace – Thermoplastic welding case study

7. LECTURE SUMMARY

8. Questions & discussion

Agenda

A-level Qualifications (2003-2005)

(HNC) FdSc Engineering Design and Manufacture (2008-2010)

Member of the Institute of Engineering and Technology (2010)

BSc (Hons) Mechanical Design and Manufacture (2011-2013)

MSc Advanced Materials (2013-2016)

Member of the Institute of Materials, Minerals and Mining (2016)

Chartered Engineer (CEng) and Chartered Scientist (CSci) 2016

1. Introduction – About me

Composites Technician – Bodycote Plc.

Composites Engineer – Exova UK Ltd.

Senior Composites Development Engineer / Materials and Manufacturing Development Manager – Tods Aerospace

Board Member – Mechanical/Marine Industrial Advisory Committee (UoP)

Board Member – British Composites Society (IOM3)

STEM Ambassador (STEMNET Initiative)

1. Introduction – About me

• Unitech Aerospace supplies the aerospace & defense industry with tooling,composite and metallic aerostructures and components.

• The company’s global footprint is comprised of strategically located sites providing local and immediate support to customers.

• Our solutions focus on rate production with design, development and process engineering make us the industry’s reliable lifecycle partner.

• Unitech Aerospace has proven capability on large complex military composite structures.

Composites Assemblies

Light Weight Structures

Metallic Assemblies

High temp alloy engine components

Composites Assemblies

Light Weight Structures

Weapons Pylons

S92 Inlet Ducts

Trent XWB

Drains Mast

AW159 Engine Exhaust Ducts

KC 390

Rear Fairing

Naval Sonar Domes, composite

structures

Surface Ship Sonar Domes

Submarine Sonar Domes

2007 2012 2013 2016

Resin Transfer Moulding

Compression & Injection Moulding

Hayden, Idaho, US Derby, Castle Donington, UK Yeovil, Somerset, UK Portland, Dorset, UK Cleveland, Ohio, US

1. Group manufacturing capabilities

680 Orders

€200m Unit Cost

€135.60 Billion

930 Orders

€173m Unit Cost

€160.89 Billion

90 Orders

€14.5m Unit Cost

€1.28 Billion

3173 Orders

€160m Unit Cost

€507 Billion35%50% 40%

55%174 Orders

€105m Unit Cost

€18.27 Billion

30%

1. Composites in aerospace and defence?

“Composite materials are constructed from two or more distinctly different materials which when combined give performance characteristics that are

different to that of their constituents”

WHAT ARE WE TRYING TO ACHIEVE BY USING A COMPOSITE MATERIAL?

Physical Properties

- Mass/Density

- Operating Temperature/Tg

- CTE

- Chemical Resistance

Mechanical Properties

- Stiffness

- Strength

- Fatigue Resistance

- Impact Strength

- Fracture Toughness

Specialist Properties

- Electromagnetic

- Acoustic

- Electrical Conductivity

- Thermal Conductivity

- Fire Resistance

2. What is a composite material ?

• Laminate Individual plies of material containing continuous fibres (woven fabric reinforcement, non-woven reinforcement and unidirectional reinforcement common)

• Sandwich StructureIndividual laminates (or skins) separated by very low density core structures. Foam and honeycomb cores used

• ParticulateShort fibres, granules powders dispersed within the material structure

……and combinations/hybrids of the above types are also possible

2. What is a composite material ?Types of composite structure

• Glass fibre (E-glass,S-glass)2.4-2.6 g/cc, strength ~2000-4750 MPa

• Carbon fibre1.7 g/cc, strength ~4800 Mpa

• Aramid fibre (Kevlar™)(polyparaphenylene terephalamide)1.45 g/cc, strength ~3000-3750 MPa

• Other fibresUHMWPE (Dyneema), Thermoplastics, Aluminium Oxide (Alumina), Silicon Carbide, Graphite

• Natural fibresHemp, Flax, Kenaf, Sisal

Materials Density (g/cm3)

Tensile Strength

(MPa)

Young modulus (GPa)

E-Glass 2.55 2000 80

S-Glass 2.49 4750 89

Alumina (Saffil)

3.28 1950 297

Carbon 1.77 2900 525

Kevlar 29 1.45 2860 64

Kevlar 49 1.45 3750 136

2. What is a composite material ?Types of reinforcement

• Thermoset polymersEpoxies, Polyesters (together accounting for 80% of the composites market) Phenolics and Vinylesters +more

• Thermoplastic polymersPolyethylene (PE), Polypropylene (PP), Polyamide (PA), Polyethyleneterephalate(PET), Polyetherimide (PEI), Polypheylenesulphide (PPS), Polyetherketoneketone (PEKK), Polyetheretherketone (PEEK) +more

• Bio-resinsBio-based Epoxies, Bio-based Polyurethanes

Unidirectional Carbon/Epoxy Composite, 44 %vol. Carbon-fibre,

0.007mm Diameter (100X)

Reinforcing C Fibre (Cross-

section)Epoxy Polymer Matrix

‘filling the gaps’

2. What is a composite material ?Types of polymer matrix

3. Composites joints - Introduction

In (Niu, 1992) it is described that for the implementation of a fibre reinforced composite joint there are six key observations to be made, which in turn will influence the choice of method or joining the structure together;

1. The loads which will be transferred across the joint (extent and direction)

2. The joint area (or region) over which this load will be transferred

3. The geometries and elastic properties of the members or components to be joined

4. The environment to which the assembly will be subjected

5. The weight and cost efficiency requirement of the joint

6. The expected reliability requirements (fatigue?)

3. Composites joints - Introduction

The above six observations were again highlighted in (Kelly, 2004) and were generally described as ‘structural/material constraints, however this thesis also suggested there are ‘design/aesthetic’ considerations required which included;

7. Disassembly requirements

8. Outer joint surface finish and appearance requirements

Furthermore from (Kelly, 2004) it is shown there will also be ‘manufacturing & commercial constraints’ to the choice of joining technique such as;

9. Assembly time

10. Processing (i.e. bonding/fastening) time

11. Surface preparation and/or hole drilling requirements

12. Lead-time/delivery

3. Composites joints - Introduction

FAILURE CONSEQUENCES

Explored in (Duthinh, 2000) is that of the ‘failure consequence’ of the composite joint in service the identification of the structural importance of a joint is critical in defining the appropriate joining technique

• Primary structural joints, the integrity of which is paramount in the safe operation of the total product. This joint may contribute significantly to the ultimate strength and stiffness of a whole structure and a failure of the joint would be instrumental in the failure of an assembly to the extent which could endanger human life

• Secondary structural joints, which will provide some strength and stiffness to the assembly however failure of the joint will not cause damage to components other than those which the joint connects together and a failure of which may have cost implications but not directly provide a risk to human safety

• Non-structural joints, ones which are not in any way associated with the stiffness and/or strength of a global assembly and the failure of which will pose little or no risk to human safety and will result in a moderate to little financial cost. An example of this may be the joining of a decorative composite panel to an aircraft/train cabin interior for example

3. Composites joints - Introduction

KEY STATEMENT

With 11 key observations to be made and a 3-tiered failure consequence classification, the choice of technology to create a composite joint is application-specific and complex

So…Understanding the various joining methods available for composite structures and knowing the strengths or weaknesses of each method is a fundamental requirement for an composites design/research or manufacturing engineer

LET US DISCOVER SOME JOINING TECHNIQUES…

4. Methods for thermoplastic and/or thermosetting polymer matrix composites

Topics covered :

a) Mechanical fastening

b) Adhesive bonding

4. Methods for thermoplastic and/or thermosetting polymer matrix compositesa) Mechanical fastening I :

• The use of mechanical fasteners for polymer matrix composites is not dissimilar to the use of mechanical fasteners for any other material

• When two components/structures are to be joined together a hole/recess will be either pre-manufactured or drilled into one or more of the substrates and a separate fastener will be used to mechanically join the two components

• These fasteners may include screws, bolts or rivets for example, which will be chosen for the given structural demands, materials and design allowables

4. Methods for thermoplastic and/or thermosetting polymer matrix composites

Figure 1, Example arrangement of titanium fastener using a PEI thermoplastic insert for bolting of compositelaminate. (Cooper & Conway, 2013)

a) Mechanical Fastening II;• Joint geometries can be numerous, however typically the joint will connect two or more

parallel faces of composite material (lap joint, double lap joint etc)

• The joining of carbon fibre reinforced composites to metals poses problems, as the materials can have a high difference in electrical potential

• A wide difference in electrical potential can increase the rate of corrosion damage of the fastener and/or any metal assembled against the carbon fibre laminate

• Aluminium, magnesium alloys and non-corrosion resistant steels are particularly a problem, however some metal alloys such as those of titanium, nickel and cobalt are more compatible with carbon fibre, hence why typically used for fasteners developed for the joining of composites

Highly Cathodic

Highly Anodic

4. Methods for thermoplastic and/or thermosetting polymer matrix compositesa) Mechanical fastening – Advantages :

• Mechanical fastening in engineering is a mature technology, there is confidence in the reliability of the method with well-defined standards and practices

• Much of the previously developed technology can be easily applied to composite materials

• Mechanical fastening can be a non-permanent joining method and can allow for simple disassembly during repair and inspection

• Mechanical fastening alone has typically little or no requirement for surface preparation and/or cleaning, with parts being able to go to assembly direct from manufacture

• Mechanical fastening can be a quick operation using traditional metal-working hand tools for assembly

4. Methods for thermoplastic and/or thermosetting polymer matrix compositesa) Mechanical fastening – Disadvantages :• Mechanical fasteners such as bolts or rivets increase structural weight which is a prime

concern for lightweight composite structures

• When coupling carbon fibre to aluminium or magnesium alloy components (typically in aerospace and automotive structures) there is an increase to the potential for galvanic corrosion

• Holes must be drilled. This means that continuous fibres in a laminate become cut/damaged during drilling and/or countersinking, which results in a depreciation of the local mechanical properties

• Mechanical fasteners can be difficult to install and/or replace in locations where a tool is not able to access the front or back of the assembled structure (i.e. for repairs on service aircraft or for interior train/automotive panels for example)

• Mechanical fastening metal substrates is easier as they can tolerate dimensional inaccuracy due to plastic yielding, however composite materials have little or no ability for plastic deformation and therefore careful design and precision of cutting is paramount to ensure good fit

• Mechanical fasteners (heads) may compromise the aero/hydrodynamic capabilities on the joint outer surface

4. Methods for thermoplastic and/or thermosetting polymer matrix compositesMechanical fastening - Reference material :

AVAILABLE

ONLINE

http://publications.npl.co.uk/npl_web/pdf/matc65.pdf

4. Methods for thermoplastic and/or thermosetting polymer matrix compositesb) Adhesive bonding I :

• Adhesives are intermediate materials which cure or harden usually from a liquid phase to a solid phase to form a joint between two parent materials

• Joints are formed from a variety of different adhesion mechanisms

• When considering all industrial sectors adhesive bonding is the most commonly used joining method for composite materials

• When bonding to a composite surface the adhesive interacts predominantly with the polymer matrix, with a smaller interaction with the reinforcement

4. Methods for thermoplastic and/or thermosetting polymer matrix compositesb) Adhesive bonding II;

There are three dominant ‘adhesion mechanisms’ to be considered…Mechanical Interlocking:

This is a physical interaction between the adhesive phase (once cured) and the profile of the substrate surfaces. Mechanical interlocking enhances the other adhesion mechanisms achieved below. Particularly beneficial for shear strength increase, not so useful for tensile pull-off load case.

Molecular/Atomic Adhesion (primary bonds, secondary forces and acid-base interactions):

This mechanism involves various intermolecular forces between similar or differing atomic and/or molecular entities on either side of the joint interface. The strongest bonding forces are achieved with primary bonds such as ionic or covalent bonding. Surface area available for bonding increases adhesion potential.

Molecular Diffusion:

The principle of diffusion theory is particularly relevant to composites containing thermoplastic polymers and when dealing with two (or more) substrates which have similar solubility parameters and/or melting temperatures. Polymer chains physically diffuse across the joint interface. This theory is relevant when using both solvent based adhesives.

MORE TO COME FOR DIFFUSION UNDER ‘WELDING’ LATER ON!

4. Methods for thermoplastic and/or thermosetting polymer matrix compositesb) Adhesive bonding - Advantages;

• Adhesives have a variable bond-line thickness and can therefore help to mitigate differences in profile and can help to counteract any mismatch as a result of manufacturing tolerances or surface porosity of the composite

• Adhesives act as a joint ‘sealant’, can reduce the level of environmental interaction at the joint and can decrease moisture absorption/permeability

• Adhesives provide an evenly distributed bonding force, serving to reduce the ability for localized stress concentrations during loading (i.e. compared to bearing stresses and hole stresses in a mechanically fastened composite joint for example)

• Adhesives with specific elastic properties and/or atomic adhesion characteristics may be selected to control stress distribution for dissimilar substrates

• Adhesives do not compromise the outer surface geometry of the composite, so aero/hydrodynamic performance over a joint outer surface may be maintained

4. Methods for thermoplastic and/or thermosetting polymer matrix compositesb) Adhesive bonding – Disadvantages;• Adhesives used on composites often have strict surface preparation requirements; this

can involve solvent cleaning, corona discharge, heat treatments, or chemical etching/abrasion of the bond surface to increase the surface area and to promote Mechanical 'interlocking' opportunities for the adhesive

• Adhesives require specific cure schedules which can differ greatly dependent on the adhesive type, from epoxy cure cycles requiring in the region of 3-4 hours at elevated temperatures, to brittle acrylic adhesives requiring a matter of minutes under minimal pressure at room temperature

• Adhesive bonds are often considered permanent and disassembly is difficult to achieve

• Adhesives are susceptible to the operating conditions which can limit the operating temperature compared to mechanical fastening or can decrease the maximum exposure time of a component to a certain environment (humidity/chemical/fuel etc.)

• Some polymers have low ‘surface free energy’ (the surface energy available for interaction with an adhesive), thus can be difficult to bond to. PE and PP great examples, PTFE (Teflon™) has the lowest free energy, think frying pans !

4. Methods for thermoplastic and/or thermosetting polymer matrix compositesAdhesive bonding - Reference material;

5. Methods for thermoplastic polymer matrix composites only

Topics covered :

a) Fundamentals of welding

b) Induction welding

c) Ultrasonic welding

d) Resistance welding

5. Methods for thermoplastic polymer matrix composites onlya) Fundamentals of welding I :

PE, PP, PPS, PEEK PEI, PES, PC, PMMA

5. Methods for thermoplastic polymer matrix composites onlya) Fundamentals of welding II :

The use of thermoplastic matrix composites in various industries is an established market, however has ever increasing scope within the transport and construction sectors

• Rapid manufacturing processes (i.e. melt/freeze cycles)

• Easier repair options (i.e. melt, re-shape)

• End of life recyclability (i.e. melt, re-shape, recover)

• Benefit of making joints in structures by welding!

Welding techniques are not yet used as readily for primary/secondary joints as adhesives, mechanical fasteners or hybridised techniques, there is a lack of historic confidence!

As demand for thermoplastic composites increases so do opportunities for welded joints

There are various welding techniques that are used depending on materials, joint sizes/geometries or for substrates of differing thickness

5. Methods for thermoplastic polymer matrix composites onlyb) Induction welding I :• Induction welding is a process that exposes the weld region to alternating electromagnetic fields which

induces eddy currents to a conductive part of the composite (i.e. carbon fibre reinforcement)

• These eddy currents induce heating of the surrounding thermoplastic

• When combined with the application of pressure can produce molecular diffusion & weld

• Eddy currents are generated using an electromagnetic coil which can be automated to operate with repeatable accuracy

• Glass or aramid (non-electrically conductive) composites require an additional conductive implant (or susceptor) material placed in the weld interface

• Implant/susceptor may be a thermoplastic film impregnated with carbon-black, iron shavings, iron oxide particles (or other ceramics) and also metallic meshes including stainless steel and copper

5. Methods for thermoplastic polymer matrix composites onlyb) Induction welding – Advantages :

• Induction welding is the most established technique for thermoplastic welding of composite materials and the practice of using induction coils to generate heat for joints is well established in the packaging and automotive sectors.

• Induction is also used to heat-cure thermosetting polymer adhesives and to provide energy for in-situ hot melt adhesives (such as modified polyethylene for example)

• Induction welding is non-contact and safe as heat is developed only within the welding seam

• Induction welding is fast and able to be suitably automated for rapid joining

5. Methods for thermoplastic polymer matrix composites onlyb) Induction welding – Disadvantages :

• Implant materials may compromise the weld strength, increase the opportunity for crack propagation (fracture) and reduce the structure’s integrity for electrical insulation, this is of particular concern for applications of lightning protection in aerospace environments

• There may be a limitation to the geometry able to be welded as the design must allow the induction to get coil close proximity to the joint surface

• There is a limit to the maximum thickness of substrate which can be welded (dependent on the density and relative ‘induction-transparency’ of the materials being welded)

5. Methods for thermoplastic polymer matrix composites onlyc) Ultrasonic Welding I :• Ultrasonic welding uses a ‘sonotrode’ which is coupled to a transducer that converts

electrical energy to oscillating mechanical movement via the rapid expansion and contraction of piezoelectric ceramic discs

• The application of a very high frequency (typically 20-40 kHz) pulse of mechanical motion through the sonotrode and onto the surface of a weld seam (under pressure) causes molecular motion

• Friction forces at the interface generates heat and causes molecular diffusion and under pressure the weld is formed

5. Methods for thermoplastic polymer matrix composites onlyc) Ultrasonic welding – Advantages :

• Ultrasonic welding is a well-established technique for joining thermoplastics and technology and equipment is highly transferrable to thermoplastic matrix composites

• The use of mechanical motion is a very safe technique and requires little H&S governance compared to other welding methods

5. Methods for thermoplastic polymer matrix composites onlyc) Ultrasonic welding – Disadvantages :

• Due to the requirement for at least one of the welded parts to be in contact with the entire surface of the sonotrode, ultrasonic welding can be limited to the weld size. It is best suited to smaller scale weld applications such as thermoplastic inserts for example

• Ultrasonic welding is limited in its applicability to low modulus thermoplastics. Low modulus dissipate the mechanical stresses and heat development is therefore poor (Ageorges, et al., 2001). This is also true for high-thickness substrates

• There are limitations to the geometries that can be welded due to the requirement for the sonotrode access to the weld surface

• The welding technique is a ‘contacting’ process which may induce unwanted stresses into the substrates

5. Methods for thermoplastic polymer matrix composites onlyd) Resistance welding I :

• Resistance welding uses a secondary material (or welding element) placed into the weld interface area

• Requires the passing of an electrical current through the electrically resistive element,

• It is essential however the element is permeable as to allow diffusion and the weld to be achieved.

• Heat energy into the weld seam is proportional to the current (��) the element resistivity (��) and time (��) via Joule’s law as follows (Stavrov & Bersee, 2005);�� = ��2����1&2. Carbon fibre reinforced thermoplastic substrates to be welded 3. AC power supply 4. Connecting electrodes 5. Heating element 6. Electrodes integrated into the PTFE tooling 7. Plunger operated electrical safety switches

5. Methods for thermoplastic polymer matrix composites onlyd) Resistance welding – Advantages :

• This technique is employable irrelevant of the composite thickness. As the heat is generated directly at the weld interface the substrate thickness theoretically does not hinder the welding (when compare to induction welding for example).

• The sacrificial welding element which remains in the joint has the potential to be re-heated should there be an insufficient weld, or possibly for reasons of future repair.

5. Methods for thermoplastic polymer matrix composites onlyd) Resistance welding – Disadvantages :

• The sacrificial conductive material left in the weld area can cause structural issues with respect to the shear strength of the joint, particularly with copper meshes there can be a tendency for cracks to preferentially propagate along the copper/thermoplastic interface (Hou, et al., 1999)

• The sacrificial conductive material left in the weld area can cause electrical issues during component operation and must be isolated entirely from any carbon fibres. Galvanic corrosion a possibility!

• Conductive metal mesh elements within the structure risk transfer of charge and the propagation of damage during lighting strikes

• Conductive meshes (metallic and non-metallic) together with any mechanisms of isolation employed between the element and the carbon parts can increase the overall weight of an assembled structure

6. Thermoplastic composite welding – Tods aerospace case studyThis process introduction shows the outcomes from a development programme funded by the National Aerospace Technology Exploitation Programme (NATEP) and sponsored by Rolls-Royce.

Development of a resistance welding technique that does not use metallic embedded implants

Consortium of active partners included; National Composite Centre (NCC) and TenCate Advanced Composites.

6. Welding elementsIR imaging shows thermal profile of each welding element, min/max temperature

difference has been reduced to ± 10°C of required processing

Non-Optimised Element

Optimised Element

Manufacturing process developed which can produce batches of multiple elements

Constructed from specific lightweight non-woven material consolidated (Void% <2) with

thermoplastic (Patent Applied For.)

Thermal Optimisation

• Manufacturing a top-hat stiffened test sample/demonstrator

• Thermoformed/cut parts are assembled into the welding fixture

• Standard weld parameters used, each joint formed successively without disassembly of the fixture

• 5x welds completed in one single process

6. Process demonstrator 1.

• Manufacturing an aerospace leading-edge product demonstrator

Flat Cetex ™ PPS Laminate

Cetex ™ PPS Curved leading- edge (thermoformed)

Cetex™ PPS C-section rib stiffener (thermo-formed)

Weld region (~40mm)

• Thermoformed/cut parts are assembled together and rapidly welded.

• Two welds performed in one process.

6. Process demonstrator 2.

43

6. Weld quality – Micro-section

Parent laminate #1

Parent laminate #2

Welding element (weld region)

No voids, no material degradation, full consolidation, high quality.ALL-COMPOSITE! No metals.

Direction of Heating

Composite surface unaffected

Composite surface unaffected

• Consistent high strength welds with good fatigue properties.

• Welding achieved with low cost equipment and materials.

• Heating to welding temperature can be achieved within 3 minutes.

• Welding process can be completed within 10 minutes (lower times

possible with force cooling).

• The welding process is not limited to flat components; panels with

significant curvature can be welded.

• High quality welds achieved with no voids that pass standard

aerospace ultrasonic NDT specifications.

• Electrically conductive substrates can be welded.

• The process compliments short cycle time associated with

thermoformed composite components.

6. Highlights and conclusions

1. Design approach to composite joining is complex, there

are a lot of factors to consider.

2. In general joining composite to aluminium (or other

metals) requires careful planning to avoid galvanic

corrosion.

3. Joining methods can include (but are not limited to);

Mechanical fastening, adhesive bonding, induction

welding, ultrasonic welding or resistance welding.

4. Tods Aerospace are active in research and development

for new rapid, repeatable and low cost welding processes

for thermoplastic composites in aerospace.

7. LECTURE SUMMARY

Adams, R. D. & Wake, W. C., 1984. Structural Adhesive Joints in Engineering. 1st ed. Barking, Essex: Elsevier Applied SciencePublishers Ltd.

Ageorges, C., Ye, L. & Hou, M., 2000. Experimental investigation of the resistance welding for thermoplastic-matrix composites. Part I: heating element and heat transfer. Composites Science and Technology, Volume 60, pp. 1027-1039.

Ageorges, C., Ye, L. & Hou, M., 2001. Advances in fusion bonding techniques for joining thermoplastic matrix composites: a review. Composites Part A; applied science and manufacturing, Volume 32, pp. 839-857.

Ahmed, T. J., Stavrov, D., Bersee, H. E. N. & Beukers, A., 2006. Induction welding of thermoplastic composites - an overview. Composites Part A - Applied Science and Manufacturing, Volume 37, pp. 1638-1651.

Cao, C., 2003. Damage and Failure Analysis of Co-Cured Composite Joints (PhD Thesis), Atlanta, Georgia: Georgia Institute of Technology.

Comyn, J., 1997. Adhesion Science. Cambridge: Royal Society of Chemistry.

Cooper, S. & Conway, D., 2013. LaWoCS Technical Report, Crewkerne, Yeovil: AGC AeroComposites.

da Costa, A. P. et al., 2012. A Review of Welding Technologies for Thermoplastic Composites in Aerospace Applications. Journal of Aerospace Technology and Management, 4(3), pp. 255-265.

DeFrayne, G., 1983. High-Performance Adhesive Bonding. 1st ed. Dearborn, Michigan: Society of Manufacturing Engineers.

Dube, M., Hubert, P., Yousefpour, A. & Denault, J., 2007. Resistance welding of thermoplastic composites skin/stringer joints. Composites, Part A; applied science and manufacturing, Volume 38, pp. 2541-2552.

Duthinh, D., 2000. Connections of Fibre Reinforced Polymer (FRP) Structural Members; A Review of the State of the Art, Gaithersburg:Structures Division, Building and Fire Services Laboratory. National Institute of Standards and Technology.

Hou, M. et al., 1999. Resistance welding of carbon fibre reinforced thermoplastic composite using alternative heating element. Composite Structures, Volume 47, pp. 667-672.

Hutchinson, A., 2012. Mechanical Testing of Adhesive Joints, Oxford, England: Department of Engineering and Mathematical Sciences, Oxford Brooks University.

Kelly, G., 2004. Joining of Carbon Fibre Reinforced Plastics for Automotive Applications, Stockholm, Sweden.: Royal Institute ofTechnology.

Kelly, G., 2005. Load transfer in hybrid (bonded/bolted) composite single-lap joints. Composite Structures, Volume 69, pp. 35-43.

Niu, M. C.-Y., 1992. Chapter 5 - Joining. In: Composite Airframe Structures; practical design information and data. University of California: Conmillit Press, pp. 285-356.

Stavrov, D. & Bersee, H. E. N., 2005. Resistance welding of thermoplastic composites-an overview. Composites; Part A applied science and manufacturing, Volume 36, pp. 39-54.

6. References

THANK YOU FOR YOUR ATTENTION

QUESTIONS AND DISCUSSION ?

SEAN COOPER MSc BSc(Hons) CEng CSci MIMMM MIET

Materials and Manufacturing Development Manager

s.cooper@tods.co.uk | T: +44 (0)1460 77666

8 Cropmead, Crewkerne, Somerset TA18 7HQ UK

www.todsaerospace.com