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Guideline for Adhesive Selection
Definition of requirements made on the adhesive and the adhesive bond
Comparison of adhesive selection software
Quality Management Tools, Techniques and their Application to Adhesive Bonding
Different NDT-Methods and their Possibility to Detect Defects
The field of multimaterials across manufacturing industry is vast and growing. The DOGMA consortium shared their views on priority areas across the industrial sectors: aerospace, automotive, construction, marine and transportation. These are summarised as follows:
| Aerospace: | 2xxx and 7xxx series aluminium alloys joined to CFRP and GFRP |
| Automotive: |
steel (incl Zn coated) and 5xxx and 6xxx series aluminium alloys to plastics (e.g. RTM and PET) and polymer composites Applications: sandwich structures for roof, floor, boot |
| Construction: | steel to timber or FRP,
aluminium sandwich structures
Applications: steel joists, wooden floor boards, concrete composites beams |
| Marine: | FRP to aluminium alloys,
polymer foams and paperboard
Applications: frigate constructions (e.g. frp to steel) |
| Transportation: | 5xxx and 6xxx series
aluminium sandwich panels (containing GRP or melamine) to GRP or melamine
Applications: interior trim panels, can saloon partitions |
The issues surrounding the effective use of the above include:
This section of the DOGMA project addresses most of these issues and consolidates the experience and knowledge of the DOGMA partnership into one summary package.
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For the range of multimaterials being considered, emphasis has been placed on adhesive bonding, mechanical fastening and hybrid combinations.
Adhesive bonding is an important joining technique, used in almost all industrial sectors. For the purposes of this section, we will review organic adhesives only (inorganic systems are based on glass or ceramic materials). Adhesive bonding involves the wetting of an organic material to joint surfaces (adherends) to effect a joint between two (or more) similar or dissimilar materials. Adhesives comprise a range of thermosetting and thermoplastic materials, and are cured during the bonding process to effect maximum performance (mechanical, leak tightness etc). The reliability of the joint is critical and an important aspect of manufacture is the surface condition, especially when bonding metallic substrates.
A bewildering variety of adhesives is available from a range of adhesive manufacturers. However, it is possible to simplify the choice by classifying the adhesive, and this can be done either by the way they are used or by their chemical type. The strongest adhesives solidify by a chemical reaction. Less strong types harden by some physical change. The major classifications are:
Anaerobics
Anaerobic adhesives cure when in contact with metal and air is excluded, e.g. when a bolt is home in a thread. They are often known as 'locking compounds', being used to secure, seal and retain turned, threaded, or similarly close fitting parts. They are based on synthetic acrylic resins.
Cyanoacrylates
Cyanoacrylate adhesives cure through reaction with moisture held on the surface to be bonded. They need close fitting joints and usually solidify in seconds. Cyanoacrylates are suited to small plastic parts and to rubber. They are a special type of acrylic resin.
Toughened Acrylics
Toughened acrylics are fast curing and offer high strength and toughness. Both one and two part systems are available. In two part systems, no mixing is required because the adhesive is applied to one substrate, the activator to the second substrate, and the substrates joined. They tolerate minimal surface preparation and bond well to a wide range of materials.
Epoxies
Epoxy adhesives consist of an epoxy resin plus a hardener. They allow great versatility in formulation since there are many resins and many different hardeners. Epoxy adhesives can be used to join most materials. These materials have good strength, do not produce volatiles during curing, and have low shrinkage. However, epoxies have low peel strength and flexibility. Epoxy adhesives are available in one-part, two-part and film form and form extremely strong durable bonds with most materials in well designed joints.
Polyurethanes
Polyurethane adhesives are chemically reactive formulations which may be one or two part systems and are usually fast curing. They provide strong resilient joints which are impact resistant and have better low temperature strength than any other adhesive. Polyurethanes are useful for bonding glass fibre reinforced plastics (GRP). The fast cure usually necessitates applying the adhesives by machine. They are often used with primers.
Phenolics
Phenolics were the first adhesives for metals, and have a long history of successful use for joining metal-to-metal and metal-to-wood. They require heat and pressure for the curing process.
Polyimides
Polyimide adhesives are based on synthetic organic chains. They are available as liquids or films, but are expensive and difficult to handle. Polyimides are superior to most other adhesive types with regard to long-term strength retention at elevated temperatures.
MS Polymers
MS Polymer is a range of silyl-terminated polyethers. The polymer has a polypropyleneoxid main chain that is terminated with dimethoxysilyl groups. It cures at ambient temperature in the presence of both moisture and a catalyst. The main chain does not contain urethane segments resulting in the absence of hydrogen bonds and in a low polarity. Both one and two part systems are available. MS polymer based adhesive/sealants give primerless adhesion to a wide variety of substrates such as metal, plastic, wood, silicon etc. It has good durability towards repeated strain and temperature fluctuations.
Due to its isocyanate free character, the MS adhesive/sealant exhibits therefore an environmental behaviour, which could be quite useful for the requirements in the sealants and adhesives industry in Scandinavia.
The following adhesives undergo a physical change and are less effective at forming an adhesive bond.
Hot Melts
Hot melts are based on modern plastics and are used for fast assembly of structures designed to be only lightly loaded.
Plastisols
Plastisols are modified PVC dispersions which require heat to harden. The resultant joints are often resilient and tough.
Rubber Adhesives
Rubber adhesives are based on solutions or latexes and solidify through the loss of the solvent. They are not suitable for sustained loading.
Polyvinylacetate (PVA)
Vinyl acetate is the principal constituent of the PVA emulsion adhesives. They are suited to bonding of porous materials, such as paper or wood, and to general packaging work.
Pressure-Sensitive Adhesives
Pressure-sensitive adhesives are suited for use as tapes and labels and although they do not solidify they are often able to withstand adverse environments. This type of adhesive is not suitable for sustained loading.
How adhesives are applied and cured depends on:
The adhesive can be applied by an automated robotic system, a bulk dispensing system or a portable hand held dispensing cartridge which allows the system to be mobile. Adhesives can even be applied by hand with a spatula. Which application method is chosen really depends on the volume of adhesive being used. With respect to the two part epoxies and polyurethanes, mixing and metering of exactly the right amount of component parts are vital for optimum performance of the adhesive. Equipment exists which can provide both exact metering and full mixing, as well as dispensing in exactly the right position for manufacturing the product. In the case of heat curing either one-part paste or film adhesive, platens, autoclaves and vacuum presses may be required.
The many advantages of adhesives include:
All these advantages may be translated into economic benefits: for example improved design, easier assembly, lighter weight (inertia overcome at lower energy expenditure), and longer life in service.
Among their limitations are:
Nevertheless, even materials which are traditionally difficult to join can be bonded with adhesives, although some substrates may give rise to lower bond strengths or durability.
When designing an adhesively bonded joint it is necessary to:
The strength of a joint is a complex function of the stress concentrations set up by the load. In a simple lap joint made from thin metal sheet there are two types of stress: shear and peel. The shear stress varies along the length of the joint with concentrations at the ends. The peel stress acts at right angles to the lap joint, and is likewise a maximum at the ends. The peel stress tends to distort the joint and consequently weakens it.
Alternative joint designs are presented in Fig.1. In these the stresses are more evenly distributed, resulting in joints of greater strength. These joints can be applied to more complex geometries including the stiffening of large thin sheets, strengthening around apertures, bonding of multilayer structures, and joints using profiles.
Bonding advantages gained through joint design can be meaningless if the surfaces to be bonded are not adequately prepared. The amount of surface preparation depends on the required bond strength, desired environmental ageing resistance and economic practicalities. For maximum strength structural bonds, paints, oxide films, oils, dust, mould release agents and all other surface contaminants must be completely removed. There are four principal ways for preparing surfaces:
Given the correct adhesive and the appropriate surface preparation almost any substrate can be bonded, provided that the operating conditions are not too extreme. However, creation of the optimum surface can be expensive and may not be practical in many manufacturing situations. Fortunately, most applications do not require preparation at this level, and usually an acceptable compromise can be found at some point in the sequence:
Bolted joints are very effective in structural assembly by virtue of their facility to joint grossly dissimilar materials, their ease for relatively simple on-site installation and possible dismantlability. Nuts and bolts exploit the screw-fastening concept in various ways but in most applications the tightening of the fastener by applied torque induces a tensile force in the bolt which clamps the parts together under compressive load. The greatest usage of bolted assembly is in metal components which can accommodate relatively high clamping forces. The joint characteristics are often dependent on the pretensioning during assembly and the tightening torque can be used as a process control parameter. High preloads are usually desirable to reduce potential joint separation and fatigue under service conditions with dynamic loads and pressure. Also in the case of structural steelwork, bolt clamping induces higher interfacial friction for transmission of shear forces in the joint.
Most engineering applications of bolted assembly use steel bolts of a selected grade to satisfy the design load specifications. However bolts in other materials including aluminium alloys, titanium and fibre composites are also used for specialised requirements.
In the context of assembly of multimaterial structures, bolting can be used both to join monomaterial components to form the multimaterial system and also to provide connections between multimaterials such as sandwich panels for large structures. In either case it is probable that at least one of the elements of the assembly may be a polymer composite material and special design principles should be observed to overcome specific problems associated with fastening of frp. These include the discontinuity of the fibres at the holes through the components and the relatively low crushing strength of the composite. Additionally the presence of carbon fibres can introduce galvanic corrosion problems.
Generally these limitations are addressed through a combination of selective orientation of fibres, the use of washers to increase the bearing surface area for the clamping force and, where necessary, specification of coated or compatible fastener materials.
Guidelines for design are given in the Eurocomp Design Code which identifies the following parameters which need to be considered.
(a) Design parameters
(b) Material parameters
(c) Fastening parameters
Click here for more information on Mechanical Connections in Polymer Composite Materials (a paper by A R Hutchinson).
A number of threaded fastener variants have been developed for multimaterials including Bighead Bonding Fasteners and threaded inserts which can be moulded in to components or adhesive bonded as a secondary attachment.
Riveting was considered to be uneconomical for a long period of time. Then, riveting was rediscovered as a rational technology of high quality especially for applications in the aerospace industry.
There are four different types of rivets used for producing undetachable (permanent) joints: solid rivets, blind (pop) rivets, huck bolts (screw rivets) and punch rivets.
Solid rivets are one-piece joining elements in which the rivet shaft is plastically formed into the closing head. Such rivets can only be used for components which are accessible from both sides.
Huck bolts (screw rivets) are used for highly stressed rivet joints. Since screw rivets are made of high strength materials which can not be formed easily during assembly, a closing collet (self-locking nut) is fixed on to the rivet.
Blind (pop) rivets, including the multi-functional types, consist of one or more elements and require only accessibility from one size.
Punch rivets are designed to be self-piercing, no need to form holes previously in the parts that are to fastened.
Rivets are classified according to the shape of the rivet head formed during the riveting.
Generally, blind rivets consist of a hollow shaft and a pull-stem (mandrel) which serves as a tool for forming the closing head. The rivet is mounted by pulling the stem out with a special tool, whereby the stem head is drawn into the protruding rivet material to form the closing head. When the pulling force exceeds a certain level, the stem breaks at a predetermined position. The breaking point can be chosen to lie either in the shaft or at the rivet head.
Mechanical fasteners using auxiliary fastening elements should be chosen so that both fastener and the components to be joined are compatible as far as corrosion and recycling aspects are concerned. The parts which come in contact with each other must have similar electrochemical potentials and the material combination used must be tolerant with respect to recycling.
Self-piercing riveting is a riveting process which requires no pre-drilled hole in the sheets to be joined thus eliminating the need for aligning prepared parts and then placing these correctly in the rivet setting equipment. A punch and die are used to complete the joining operation in a single step. The punch drives the rivet which pierces the top sheet and is set into the workpiece by partially piercing the bottom layer. A shaped die (or anvil) on the underside reacts to the setting force and causes the rivet tail to flare within the bottom sheet. This produces a mechanical interlock which includes the added rivet joining element and creates a button in the bottom sheet.
Fig. 2 Self-piercing riveting sequence with a semi-tubular rivet
The length of the rivet tail, hole diameter and hole depth to shank diameter, and the design of the tooling used mainly determine the final shape of the rivet and of the button on the underside of the joint. Modifying the shape of the end of the shank of the rivet or the shape of the die can alter the manner in which the rivet flares as it is set.
There is a wide choice of rivet forms. The rivet is generally semi-tubular but may also be solid. Countersunk heads can provide a flush finish in the top sheet and even be colour matched to organic-coated or pre-painted material.
Where dissimilar materials are being joined, the rivet is generally applied in the direction of thin to thick or low strength to high strength material for best results. This enables the thinner or softer material to be secured by the rivet head while the flared shank of the rivet is anchored in the stronger or thicker lower sheet. This is the opposite of the preferred direction for clinching.
A number of companies have developed proprietary rivet and tooling designs and have produced systems which can compete, in terms of manufacturing operation and joint performance, with resistance spot welding for some applications.
The key advantages of self-piercing riveting (for the automotive sector) compared to spotwelding, are:
-better fatigue performance both in steel and aluminium
-lower scatter in quality
-lower scrap cost
-better properties in aluminium
and the disadvantages are:
-need for greater press forces when joining steel leading to big C-frames
-different sheet thickness combinations need different rivets
-part price for rivets.
A further advantage of the process for other sectors is the ability to join materials which are otherwise difficult or impossible to spot weld. There is interest in joining heavy zinc-coated (galvanised) steels for building, heating and ventilation applications. Here the greater difficulty of controlling of the spot welding process, short electrode lives and the local loss of zinc corrosion protection owing to vaporisation during welding, all makes the riveting process very attractive.
Other materials such as organic-coated and pre-painted steels can be joined by self-piercing riveting which is of interest to the automotive industry. These materials are usually unweldable. Riveting of pre-finished material can eliminate the need for post-joining painting of parts. Finally, the ability to join dissimilar materials such as aluminium and steel opens up opportunities for the process, particularly in the automotive industry where such material combinations are desirable for achieving weight savings.
Joint Design
The flange width, or distance from the edge where the rivet is to be placed, must be sufficient to ensure that there is material to contain the deformed rivet and sheet. The button may otherwise burst out of the edge of the flange or cause distortion in the joint. Proper overlap of the layers to be joined and a correct flange width will also help ensure proper alignment between the workpiece, punch and die. A pre-clamping step may be helpful if joining a flange width close to the minimum width is to be undertaken.
Rivets should be spaced to avoid contact with previously driven rivets or the strained area immediately around them. Since the rivets are made of harder material than the layers to be joined, riveting over an existing joint may result in serious damage to the tooling. Placing several rivets too near to each other may cause distortion or some bending of the joint. A pre-clamping step can help to minimise this. A sufficient number of rivets must, however, be used to guarantee the overall design strength of a section.
A precise relationship between part fit-up, alignment and joint quality is not easy to quantify. However, good control of these two variables will help ensure that the layers of material to be joined are drawn together properly as the rivets are driven and set. In addition, force will not be diverted into pressing parts together before the actual joining operation. Poor fit-up and alignment may reduce joint performance and accelerate tool wear.
Recommended Joint Design
Clinching (also known as press joining) is similar to self-piercing riveting, except that the rivet is replaced by a punch which forms the two materials to be joined, into a die, Fig. 3. A button is formed on the underside and provides an interlock between the sheets.
Fig.3 Clinching sequence three segment split die type.
Information on edge connections for multimaterials structures can be found at http://www.inf.vtt.fi/pdf/tiedotteet/1997/T1862.pdf
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Performance profile - Specification
In this part of the text,
first all the factors to consider will be treated, then some examples of
an adhesive selection procedure will be presented. For the success of an
adhesive bond it is absolutely necessary to carefully list up the requirements
made on the adhesive bond. All the requirements the adhesive bond has to
meet from the start of its processing to the end of its lifetime need to
be considered. So the application of the bonding technique demands careful
planning, regarding personnel, technical and economic conditions.
As well as the exact knowledge of the material/material combination to be bonded, the essential conditions for optimal adhesive bonds are the right choice of the design construction, the procedure to be applied and -especially important- sufficient knowledge of the stresses involved. Essential for the load tolerance of the joint is not the initial strenght, but the lowest level to which this strength will fall during the life of the structure due to the adverse effects of the ambient enviroment.
The critical procedure for the planning of a bonding technical solution has to pay attention to material specific and processing-specific parameters. To estimate the influences of stress the designer must be clear about the conditions under which the adhesive bonds will be produced and used.
For such a concept it is recommended to integrate all persons involved (planning, design, production, research and development, producers of the adherends, suppliers of the adhesives, user) from the beginning, in all matters of development and execution.
Generally the selection of an adhesive is almost always done with regard to the material's ability to be bonded. This procedure cannot do justice to an optimal use of adhesive bonding. As well as the adhesive/material-combination the production-specific aspects and the future conditions of stress have to be considered equally.
Today it is possible to bond most the industrially used materials with synthetic adhesives. The essential difference is not found in the formation of a sufficient adhesive strength to the adherends but in the properties of the adhesive layers formed by them under mechanical stress or long term influences. So for the selection of an adhesive the following essential influences have to be considered: material and material combinations, manufacturing processes, type of adhesive and stress. The procedure concerning the adhesives selection is the result.
Influences
Material and material combinations
- The kind of material or material combinations have to be fixed exactly. That means to identify the exact alloy in the case of metals or blends in the case of plastics. For plastics a differentiation of thermosets and thermoplasts must be done. Especially for plastics blends it is possible that the "same" type of plastic (e.g. toughened ABS) from different suppliers may have very different characteristics! Also the effect of a surface pretreatment may be very variable. The general features of these properties can be evaluated. Care must be taken not to easily take them for what they should be.
- The mechanical-technological properties of the adherends which have to be combined are mainly stability values, thermal expansion, thermal conductivity.
- The surface properties are very important for the adhesion and therefore for the stability of the whole adhesively bonded structure. The existing layers on the surface, the geometric structure, the wetting behaviour, the diffusion- and solubility-properties (especially for thermoplastic adherends) have to be considered.
Manufacturing processes
- The size of the structure is related to its design. The possibilities for adhesive bonding technology have to be regarded realistically. This is also valid for the dimensions of the bonded area. Other points which have to be considered are temperature-bearing capacity and compressive load.
- The consideration of production sequence is essential for adhesive selection. Firstly the type of production has to be analyzed. Is it a single part production or a batch production? For single part production a smaller amount of adhesive is needed. Fixtures can be used. That means the curing of the adhesive can consume more time compared to a batch production.
- In the case of a batch production the main question is: Is it a small or large series production? The cycle time determines the number of adhesives which can be applied. Fixtures often cannot be used. The number of items is important. A decision concerning manual or mechanized or automated adhesive application must be taken.
- The surface preparation is dependent on the kind of material/materials combination and the production. Firstly it must be decided whether there is a necessity for surface preparation. If such a preparation is needed, its integration into the production process has to be analyzed. For batch production, often surface preparations are not possible. If the materials combinations in such a case need a surface preparation the material must be substituted. If a surface pretreatment is necessary the controlled disposal of surface pretreatment substances must be resolved.The application method is correlated to the type of production: manual, mechanized, semi-automated, automated production.
- The use of fixation of the adherends is dependent on the type of production and is dependent on the type of adhesive. If a fixing is needed adequate fixtures must be used. A fixing by the adhesive or a fixing by other joining techniques must be considered. If a fast curing adhesive is used an exact positioning but only a little fixation is needed. Slow curing adhesives enable positioning after putting-together but need long fixation times.
- The selection of the adhesive with its curing mechanism is determined by its integration into the production process. For batch productions short time curing adhesives are often better. In other cases of production other types of adhesives can be applied.
Other factors to be considered include:
- The integration of adhesive bonding technique in the production processes is subject to the protection of the environment and maintenance of industrial health and safety standards. The protection of the personnel and creating of adequate working environments guarantee that adhesive bonding techniques will be carried out to highest standards. The tolerance band or the tolerance limit is a further factor in selecting adhesives. It depends on the adherends and a precision of production and determines the adhesive with its curing time and curing temperature.
- quality assurance requirements (e.g. QA-Systems, destructive and nondestructive testing)
- post production stages
- production costs
Type of adhesive
- Processing considerations. It has to be considered how much time is consumed in the adhesive bonding process in production. The temperature for the adhesive curing has to be correlated to economic and ecological requirements as well as to the materials which have to adhesively bonded. For a batch production, the curing of the adhesives together with other production stages (e.g. lacquer curing) has to be considered. Furthermore, the adhesive dosage and the mixing process for two-component adhesives must be reproducible. Factors such as melting, and solvent removal have also to be considered.
Concerning a general overview a suitable procedure follows. Now that you know what factors are important in adhesive selection we can discuss the best selection procedure. One must be aware that most of the stages we present have an influence on each other. Consideration from stage 4 may necessitate changes to the conditions defined in stage 1. Also very often pre-set conditions will be altered either by a well thought decision or by an impulsive decision: just let's change.
1st stage:
Definition of the material and the corresponding characteristic values according to the criteria given previously at the point "Material and Material combinations": kind of material or material combinations, mechanical-technological properties, surface properties, size, design, dimensions of the bonded area, temperature-bearing capacity, compressive load.
2nd stage:
Lay-out of the design. In this context we must consider the following points: Providing sufficient bonding area. As a guide value for the overlap length (lo) is dependent on the thickness of the adherend (s). The ratio lo /s may be typically 10 to 20.
3rd stage:
Definition of the stress conditions to be expected. For a scale design allowances and safety factors the following estimated data may serve:
- dynamic stress: the dynamic stress must remain below approx. 10 - 20 % of the maximum static bonding strength
- influence of temperature (This paragraph to be rewritten)
- moisture influence: the allowance for moisture influence must be approx. 20 - 30% of the static bonding strength if corrosion does not occur.
An exact analysis of the expected stress conditions is absolutely necessary during the planning.
Determining the method of production according to the criteria given under "Manufactur ing Processes":
Some criteria for selecting adhesives.
A short curing time and/or fast initial stability can be reached by using cyanoacrylates, UV- curing adhesives, very reactive two-component systems with a short pot life (devices for mixing and dosing are required), hot-melts (temperature stability of the adherends must be considered).
For large bonding areas it is advisable to use adhesives with a long or open pot life or dispersions. The advantages of the use of adhesive films (physically curing, or chemically reacting) must be considered.
The viscosity of the adhesive must be suited to the surface (smooth, porous, foam structure) and its bonding position.
The connection between the deformation properties of the adherends and the adhesive layers must be considered. For materials with a high deformation capacity under stress and/or different thermal expansion properties adhesives with flexible properties in the adhesive layer should be used and vice versa (within certain limits the thickness of the adhesive layer can be increased).
Regarding the temperature stability it can be assumed that thermoset cured adhesive layers with a corresponding high glass transition temperature show more favourable properties compared to thermoplastics. Almost the same is valid for the creep properties under static stress.
The optimum values for the
bonding resistance (measured according to DIN 53 283) can be reached by
using cross-linked thermosets (e.g. epoxides, phenolic resins). However,
for real stress the reducing factors must be considered.
The possibilities of the recycling of adhesively bonded products have to be considered.
A general concept for quality assurance has to be developed.
The personnel's qualification and the design of work place are important requirements of adhesive bonding technology. Adequate actions have to be taken.
Appraisal of the relationship between costs and profitability.
In this context it has to be considered that the price of the adhesive systems is not the sole determining parameter. However, every processing stage which is combined with adhesive bonding technology as well as the incremental value of the adhesively bonded adherends have to be taken into account. The resulting incremental value generally is more than a dimension higher. Long-term experience shows that surprising simplifications and cost reductions can be created by the utilization of suitable adhesives.
To sum up, the following questionnaire has proved suitable for the planning of bonded technical applications:
Which materials are to be joined (exact definition, if necessary alloying composition)?
Surface condition?
Are there requirements for surface preparation?
Is there the possibility of redesigning the structure for adhesive bonding and/or in which way are the existing constructions to be changed?
What are the types of stress and the levels of stress acting on the bond? (mechanical, dynamic, static, long lasting)?
Which production considerations are there for the adhesive processing (time for curing, manual, semi- or fully automated processing)?
The level of education and qualification of the employees who carry out the "manufacturing system adhesive bonding"?
Determination of Requirements
Adhesive selection
hardening-/curing mechanisms
-(physically hardening, chemically curing)
Materials
Kinds of stress on
components
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Easelwin (in English) http://www.twi.co.uk
Windows based adhesive selection software based on generic product types. The latter web site introduces the user to a knowledge based site for joining technology. It is expected to have EASelWin live on the site by Quarter 2 2001.
GlueDo (in German) http://www.gluedo.de/
Adhesive material selection software based on products available on the German market.
Advantages and Disadvantages of the Software Packages
|
GlueDo - advantages |
Easelwin - advantages |
GlueDo - disadvantages |
Easelwin - disadvantages |
|
Easy way to get general information |
Easy way to get general information |
Not a real expert system, you need additional expert know how to assess the results |
Not a real expert system, you need additional expert know how to assess the results |
|
English language |
German language |
||
|
Comprehensive evaluation of the literature |
Generalised presentation of adhesive knowledge |
Necessity of testing in critical cases not mentioned |
Necessity of testing in critical cases not mentioned |
|
Different databases: -adhesives/sealants -adherends -construction and design -case studies -surface preparation -curing and testing -health and safety |
Different databases: -adhesives/sealants -adherends -surface preparation -curing and testing -health and safety |
Only pre-selection of adhesive types, no fine selection of particular products possible |
Only pre-selection of adhesive types, no fine selection of particular products possible |
|
Analysis of the bonding problem and set up of a list of requirements in form of a dialogue with the user |
Easy ‘what if’ analyses |
Result of search always: contact the manufacturer! |
Result of search: contact the manufacturer or alternative expert! |
|
Easy handling |
Easy handling |
Only German manufacturers |
No manufacturers identified |
|
Cheap in relation to some systems |
Cheap in relation to some systems |
||
|
Modification and enlargement possible |
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The following table can be used as a first evaluation of alternative joining processes. For further guidance on specific applications, the user should contact other experts within their own organisation or through independent Research and Technology Organisations.
Additionally, there is a French design software tool (CETIM COBRA) available for the dimensioning of bolted assemblies with a controlled prestress. It allows prestress levels to be determined, for given loading conditions, and verifies the fatigue resistance of assemblies subjected to cyclic loading. The calculations are based on AFNOR FDE 25030 and VDI 2230. The geometry, materials and mechanical and thermal loadings are entered and the software calculates stresses and strengths (from a material database if required). The fatigue behaviour is then checked and partial safety factors are determined. The programme runs under Windows, English, French and German versions are available and it includes graphics showing results. It is reported to be widely used in France. More information can be obtained from CETIM, St Etienne (Mr. R. Souvignet), 7 rue de la Presse BP802, 42952 St Etienne Cedex 9. Tel. 00 33 4 77 79 40 01.
Joining Process Comparisons
|
Process |
Resistance spot |
Blind rivet |
Screws self-tapping |
Hilti nail |
Rivet self piercing |
Clinch |
Adhesives |
Hybrid adhesive + spot method |
|
Description |
||||||||
|
Flexibility |
Moderate |
Highly |
Highly |
Highly |
Moderate |
Moderate |
Moderate |
Moderate |
|
Portability |
Moderate |
Highly |
Highly |
Highly |
Moderate |
Moderate |
Moderate |
Moderate |
|
Repairability |
Repeat on new area |
Drill and re-insert |
Yes |
Yes |
Repeat on new area |
Repeat on new area |
Complex |
Possible |
|
H&S |
Fumes generated should be extracted. Mechanical trapment |
Safe |
Safe |
Care with consumables |
Mechanical trapment |
Mechanical trapment |
Fumes possible, check safety sheets |
Fumes possible and mechanical trapment |
|
Materials |
Most metals |
Most materials |
Most materials |
Most materials, 4mm min thickness |
Most metal, some plastics |
Most metals |
Most materials |
Most materials |
|
Joint type(s) |
Lap type joints |
Lap type joints |
Lap type joints |
Lap type joints |
Lap type joints |
Lap type joints |
Lap type joints preferred |
Lap type joints |
|
Length/item |
Spots |
Single points |
Single points |
Single points |
Spots |
Spots |
Areas |
Areas |
|
Equipment |
||||||||
|
Capital cost Process Jigs |
20 to 30 5 |
1 to 5 5 |
0.2 to 1 1 |
? 1 |
60 5 |
60 5 |
10 8 |
10-60 5-8 |
|
Process |
||||||||
|
Speed mm/min |
10 sec/shot |
10 sec/shot |
30 sec/shot |
20 sec/shot |
10 sec/shot |
10 sec/shot |
Variable |
Variable |
|
Constraints/ extras |
Hole drilling |
Possibly hole drilling |
Surface preparation |
Surface preparation |
||||
|
Properties |
||||||||
|
Corrosion resistance |
Moderate |
Moderate, check rivet performance |
Moderate to good |
Moderate to good |
Moderate to good |
Moderate to good |
Moderate to good |
Moderate to good |
|
Strength |
Moderate to good |
Moderate to good |
Moderate to good |
Moderate |
Moderate to good |
Moderate |
Moderate to good |
Moderate to good |
|
Stiffness |
Moderate to good |
Moderate to good |
Moderate to good |
Moderate |
Moderate to good |
Moderate |
Moderate to good |
Moderate to good |
|
Fatigue |
Moderate |
Moderate |
Moderate |
Moderate |
Moderate |
Poor to Moderate |
Good |
Good |
|
Surfaces |
Spot burn marks upper and lower |
Projections upper and lower |
Flat upper, projection underside |
Projections upper and lower |
Flat upper, projection on underside |
Flat upper, projection on underside |
No change upper or lower |
Depends on spot process |
|
Process |
||||||||
|
Ease of use |
Easy |
Easy |
Easy |
Easy |
Easy |
Easy |
Requires skill |
Requires some skill |
|
Distortion |
Low |
Low |
Low |
Low |
Low |
Low |
Low |
Low |
|
Pre-treatment? |
Clean and grease free but has tolerance |
None, need hole |
None |
None |
Clean and grease free but has tolerance |
Clean and grease free but has tolerance |
Clean and grease free |
Clean and grease free |
|
Standard of fit-up? |
Low to moderate |
Close fit of pre-drilled holes |
Low to moderate |
Low to moderate |
Better fit-up faster processing and less distortion |
Better fit-up faster processing and less distortion |
Low |
Low to moderate |
|
Post treatment |
May be required |
None |
None |
None |
None |
None |
May be required |
May be required |
|
Consumables |
Power, air, water, electrodes |
Rivets, air |
Screws |
Nails, charge/power |
Rivets, power |
Power |
Adhesive |
Adhesive plus other dependent on spot process |
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Stages at Which to Consider Addition of Another Joining Method to an Adhesive Bond: Hybrid Joint
Adherends
Incompatibility of surface pretreatments (compromise can be taken if additional joining method used).
Curing temperature limitation (additional joining method used to retain assembly during cure).
Manufacturing Processes
Type of Adhesive
Stress
Stages at which to Consider Addition of Adhesive to ‘Localised’ Joining Method (i.e. Spot Weld, Rivet, Clinch etc)
Stress
Manufacturing Process
Precautions to take when using Hybrid Joining (i.e. Clinching, Riveting, Bolting etc with Adhesive Bonding) with Multi Materials
Hybrid Adhesive Bonding
This situation calls for a mixture of adhesives in one application. Possible problem areas which have been identified for this situation include:
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Adhesive bonding is an important joining technique which is used in a wide variety of industries (packaging, automotive, aerospace, general structural, building and construction are key ones). In many products the performance and reliability of the adhesive joint is critical to the product's performance and, sometimes, to its safe operation.
The problem of assuring the quality and reliability of an adhesive joint 's the absence of suitable non-destructive examination methods, in all but a few special cases. Therefore, inspection of adhesive bonds is not a feasible way of assuring quality and in modem manufacturing philosophy, it is after the event and is an unnecessary activity in a well controlled process. The only way to provide assurance is to systematically manage and control the whole operation from design of the joint through to final assembly. In this way, the possibility of poor quality joints being produced is reduced to the minimum because proven procedures are being followed at all times.
Every adhesive bonding situation is unique but all adhesive bonding situations have a number of common features. Consequently, this generic model is designed to cover all situations. All the major stages from design through to final assembly and inspection are listed which define the requirements, methods of quality verification and the remedial action at each stage. Each stage can be accessed individually, progressively in more detail leading ultimately to the identification of the specific measures needed for an individual application. The model QUASIAT therefore acts as guidance to the user in defining the specific quality requirements for a joint and the specific quality management actions needed to ensure the quality requirements are met.
The quality management of the adhesive bonding process relies on two major concepts:
The application of these concepts relies on the definition of the requirements (unique for each case), the appropriate information flow/decision making process and the use of quality management tools and techniques at the appropriate point in the process (see Table below).
The key determinant of the quality of an adhesive joint is the design of the joint. Design in this context includes material selection (both adhesive and adherends) and the method of joining - in other words the complete specification of the joint. Unless the joint design is completely specified then there is no basis on which to use process monitoring and there would have to be reliance on inspection of the completed joint, which is known to be unsatisfactory. Therefore the quality management of the design is of primary importance.
The process monitoring and control of the bonding process is clearly dependent to a very large extent on the type of application. In reality, it is the manufacturing activity which will require differences in the model. The key features of the manufacturing activity which determine the quality management model are:
These, in their turn, are affected by product type, adhesive and adherend type and component design. The criticality of the joint 's not a factor. Clearly, the more critical the joint the more rigorously the quality must be controlled and assured but that is determined by the detailed application of the model. (Joint criticality is also a factor in overall joint/component design).
From the concept point of view, the assembly process can be characterised in one of four ways and these lead to the four sub-models.
High production rate is considered as >10 joints/hour.
Low production rate is considered as <10 joints/hour.
Sub-models 2 and 4 relate to situations where operator skill is a determining factor (i.e. a craft based approach) whereas Sub-models 1 and 3 relate to more systems-controlled situations. It is, of course, possible that different levels of mechanisation may be applied at different stages in manufacture.
The quality-related features of the different levels of mechanisation can be summarised as follows:
High level of mechanisation: Pre-qualified procedures.
On-line measurement and process control.
Low level of mechanisation: Training.
Inspection.
Pre-qualified procedures.
The generic model are shown in the form of activity, quality requirement, method of validation/control and corrective action in the Table below.
Generic flowchart of the design and manufacturing process [QUASIAT]
|
Activity |
Quality |
Method of |
Corrective |
|
1. Specification review |
|
Review of:
|
Specification change |
|
2. Design |
Specification requirements achieved in an efficient, economic and consistent manner |
Quality Function Deployment. Failure Mode and Effect Analysis. Taguchi loss function analysis. |
Design changes |
|
3. Verification of design |
Does design satisfy requirements? |
Qualification tests. |
Design change |
|
4. Selection and sourcing of materials |
a. Joint design requirements: b. Specified component requirements: |
Test records. |
Return to supplier. |
|
5. Selection and sourcing of adhesives |
a. Joint design requirements: b. Production requirements: |
Test records. |
Return to supplier. |
|
6. Storage of adhesives |
Requirements specified by adhesive supplier: |
Inspection of packages. |
Reject. |
|
7. Pre-treatment of surfaces |
Requirements specified by (a) and (b) material properties: |
Use tested procedure (mistake proofed). |
Re-treat. |
|
8. Assembly |
a. Component fit-up: b. Application: |
Inspection. Metering by calibrated dispenser. Use of tested procedure (mistake proofed). |
Re-jig or select correct components. Reject or re-apply. |
|
9. Cure |
Requirements specified by adhesive supplier: |
Use tested procedure (mistake proofed). |
Reject or re-cure. |
|
10. Final inspection |
Joint meets design requirements: |
Test programme. |
Reject. |
|
11. Pre-use storage |
Joint meets design requirements: |
Correct storage review of test reports, supplier information. |
Reject. |
|
12. Service |
Joint meets design requirements: |
Service monitoring. |
Repair. |
This model should be studied in conjunction with the Table below. How they will be put together is dependent on how the user will wish to 'see' the model.
Tools, techniques and their application
|
Process Step |
Tools and techniques |
|
Specification review |
|
|
Design |
Taguchi |
|
Design verification |
Product testing |
|
Selection and sourcing of materials |
Product testing |
|
Pre-treating |
SPC |
|
Assembly |
SPC |
|
Cure |
SPC |
|
Final inspection |
Product testing |
|
Pre-use storage |
Product testing |
|
Service |
FMEA |
Brief remarks on the quality control methods mentioned in the Table (QFD, Taguchi, FMEA) are presented in the following paragraphs.
QFD
The foundation of QFD (Quality Function Deployment) is the belief that products should be designed to reflect customers' desires and tastes. Therefore this method is most suitable for applications that are based primarily on the detailed requirements and specifications of the customers and where interfunctional planning and communications among marketing people, design engineers and manufacturing staff are required.
Taguchi
The off-line Taguchi method defines quality control in relation to design for quality. This is a continuous quality improvement programme that includes continuous reduction in the variability of product performance characteristics about their target values. In this method statistically planned experiments can be used to identify the setting of product (Process) parameters that reduce performance variation. Therefore, this method is less suitable for applications on which performance characteristics are not based on numerical measurements, but on an order categorical scale such as Poor, Fair, Good or Excellent.
FMEA
Failure Mode and Effect Analysis is an important method to identify all possible failures and their effect on the system. The objective is to classify failures according to their effect. FMEA provides an excellent basis for classification of characteristics. When engaged in FNMA, it is wise to bear in mind that the severity of the failure is not the only important factor. One must also consider the probability of failure. One purpose of FMEA is to direct the available resources toward the most promising opportunity for improvement. As far as adhesive bonding is concerned, this method offers a quality control technique that is most suitable for low rate production (i.e. highly cost sensitive production line) and where multiple processes are interlinked.
DFMA
Design For Manufacturing and Assembly reflects manufacturing problems in an assembly line and how these problems should be handled. This technique is concerned with reducing the cost of a product through simplification of its design. In a multi-part assembly line the best way to achieve this cost reduction is:
References
Quality assurance in adhesive technology. Eureka Project EU716. Abington Publishing. Cambridge, England. ISBN 1 85573 259 9
Table 1 Different NDT-methods and their possibility to detect defects, [Engineered materials handbook]
|
NDT-method * Defect |
Manual method |
Ultrasonic method |
X-ray method |
Thermal method |
Vacuum method |
|
Defect between adhesive and adherend |
X |
X |
X |
||
|
Defect in the adhesive |
X |
X |
|||
|
Bad adhesion between adhesive and adherend |
X |
* The table is presented in the handbook "Limma med kvalitet" (eng. Adhesive bonding with quality), page 207, where the NDT-methods are presented in more detail.
Note: Where did the fault appear?
How severe is the fault?
Table 2 Example from the aircraft industry - Some common defect types and NDT-methods, [Saab Scania]. Reference: [Adhesive bonding with quality, page 208], where the NDT-methods are presented in more detail.
|
NDT-method Defect type |
Manual method Visual inspection Tapping method |
Ultra-sonic method |
Fokker bond tester |
Bonda-scope 2100 |
X-ray method |
Neutron radiography |
Thermal method |
Vacuum method |
Holography |
|
|
Void |
X |
X |
X |
(X) |
X |
(X) |
X |
|||
|
Porosity |
X |
X |
X |
(X) |
X |
(X) |
||||
|
Separation/ disbond |
X |
X |
X |
X |
(X) |
X |
||||
|
Adhesive bond line too thick |
X |
X |
(X) |
X |
||||||
|
Lack of adhesive |
X |
X |
X |
X |
X |
X |
X |
X |
||
|
Release film residuals |
(X) |
(X) |
||||||||
|
Porous, foam fillet* |
X |
|||||||||
|
Lack of fillet* |
X |
|||||||||
|
Cavitation of fillet* |
X |
|||||||||
|
Fracture in fillet* |
X |
|||||||||
|
Leak, outflow of adhesive |
X |
|||||||||
* Fillet = exceeding/overflow of adhesive, pressed out at the edge of the joint.
References
Adhesive bonding with quality - a handbook. 1994 (in Swedish) ISSN 0349-0653
Engineered materials handbook, volume 3. Adhesives and Sealants. Library of Congress. ISBN 0-87170-281-9
Saab Scania AB. Report Reg nr. TUKFF-91.330 (in Swedish)
Back to Contents
Adhesive bonding in manufacturing should be treated as a special process as defined in ISO 9001. This means that appropriate quality systems need to be put in place to ensure consistently high quality bonds are achieved. Integral to this, is the need for skilled operators who understand the bonding process and the influence of variants in this process.
Within Europe, there are many short courses available for adhesive bonding engineers, mostly run through universities or research and technology organisations. Additionally, Europe, through the European Welding and Joining Federation (EWF) has developed a European wide scheme for the training and qualification of adhesive bonders, adhesive specialists and adhesive engineers. These courses, with examination, provide certificates of competence for the candidate, which are recognised within Europe. (There is current work underway to allow such courses to be recognised internationally).
European Adhesive Bonder
Training Objectives and Target Group
The training leading to the qualification of European Adhesive Bonder (EWF 3305) requires 40 hours of study on a one week full-time course including theoretical and practical training sessions and terminal examination.
The European Adhesive Bonder will then be qualified for deployment in the production plant. He/she will acquire an understanding for the distinctive features of adhesive bonding as an evolving manufacturing method. Detailed information as concerns working with adhesives is taught in their particular contexts and the results of these are made clear. With this basic knowledge, the European Adhesive Bonder can independently carry out technically accurate adhesive bonding procedures.
Access to the training course as an European Adhesive Bonder is made easier through a self contained professional training module in the fields of applied metals and/or plastics.
European Adhesive Specialist
Description of Training Programme Structure
The training programme for the qualification of European Adhesive Specialists (guideline EWF 3301) in both theoretic and practical aspects of the field is covered as a full-time course of 120 hours (plus terminal examination). This is divided into one Basic Module and two Extension Modules each lasting 40 hours (one week). The single modules are repeated at certain intervals.
Training objectives
The qualification as a European Adhesive Specialist is intended for staff working in manufacturing or in product development. The student would acquire the ability to accurately and independently carry out adhesive bonding procedures and to set out written instructions concerning working procedures with adhesives. Through this training he/she will be able to explain technical procedures and instructions to European Adhesive Bonders both in theory and practice.
Following a successful examination result he/she will be able to lead both trainees and European Adhesive Bonders in both theoretical and practical work; this applies equally to the planning, organising and overseeing of appropriate adhesive bonding working procedures, to control process parameters and to adjust these if and when necessary. He/she should also be able to recognise irregularities and identify them as potential problems.
Practical Training
The theoretical aspects in the programme of study are realised through the practical training part of the course. In this way the student acquires the essential knowledge for his/her particular field of industry and this is instrumental in the training objectives as a means by which the specialist practical experiences in the course can be supported.
Target Groups
The training programme is targeted at employees in the industrial, craft and trading sectors who would like to broaden their qualified education by sound knowledge in the field of Adhesive Bonding Technology. Included in this target group are the following: industrial specialists in fields of metals, plastics and rubber, masters of metal crafts, craftsmen(women), technicians, DVSÒ welding practitioners, DVSÒ welding specialists, chemical laboratory technicians, workers in the chemicals industry, chemical engineers and application technicians.
Organisations providing such courses and possible certification include:
Centre for Adhesive Bonding Technology (Klebtechnisches Zentrum - KTZ) at the
Fraunhofer-Institut für Fertigungstechnik und Angewandte Materialforschung
Wiener Straße 12
D - 28359 Bremen
Contacts
Prof. Dr. Andreas Groß
tel: #49 (0)421 22 46 - 437
fax: #49 (0)421 22 46 - 430
e-mail: gss@ifam.fhg.de
Dr. Dirk Niermann
tel: #49 (0)421 22 46 - 439
fax: #49 (0)421 22 46 - 430
e-mail: dn@ifam.fhg.de
You will further information at the site on the internet at http://www.ifam.fhg.de.
Granta Park
Great Abington
Cambridge
CB1 6AL
e-mail: twi@twi.co.uk
Joining Technologies Department
Centre Technologico de Materiales
Camino de Porteutxe 12
20 009 San Sebastian
Spain
e-mail: cjimenez@inasmet.es
IVF, IFAM with others have been involved in a programme (Special Adhesive Learning System (SALS), funded under the Leonardo da Vinci Programme, to establish training course material for adhesive practitioners. Further details are available from http://www.bwu-bremen.net/iwp/iwp.html
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Trains
Huckbolt covers were originally bonded to the bodyshell of the railway vehicle (using polyurethane adhesives). A hybrid system of mechanical fastening and polyurethane sealant is currently used to provide a fail-safe design.
Construction
A paper "USING STRESSED AND UNSTRESSED COMPOSITE PLATES FOR STRENGTHENING EXISTING STRUCTURES" by Dr Sam Luke, Mr John Darby, Mr Andrzej Skwarski can read here in pdf-format.
Corus
Methods of evaluating adhesive bond durability round robin test sample geometry, tensile test machines etc. involving Alcan, Corus, Hydro, Pechiney. Result, no statistical differences.
Vrenken and Rijkhoff Adhesive bonding of Hylite 1997
Buters Hem flanging Hylite sandwich sheet for mass production 1998 (SAE paper). Result, adhesive bonding is suitable for Hylite, and most adhesives evaluated were compatible with oil.
Vrenken and dRuyter Influence of a lubricant on adhesive bonding of zinc-coated steel 1998. Result, lubricants evaluated had little influence on bondability, and adhesives identified which had best durability
ECSC Project Joining of steel to different sheet materials and product performance evaluation 1998, involving Hoesch-Krupp, CRM, Hoogovens, TNO. Result, adhesive bonding well suited to join aluminium and steel sheet, order of joining techniques from highest to lowest in measured fatigue strength was: adhesive bonding, MAG welding, clinching, laser welding, resistance pot welding, order of joining techniques from highest to lowest absorbed energy was: welding, clinching, adhesive bonding.
Gutierrez Corus internal work, Study comparing strength of mechanical, adhesive and hybrid joints. 1999. Result, adhesive and hybrid joints significantly stronger than the mechanical joints.
Volvo
Volvo is a participant in the ENJOY project which is European Training for Joining Technology within the Leonardo da Vinci programme of the European Commission.
The objective of the ENJOY-project is the development of modules for the education, qualification and certification in an European framework in the field Mechanical Joining. This leads to a standardisation of European education levels as well as to an increase of the application of mechanical joining techniques.
Oxford Brookes University
Broughton J Composite Connections in Structural Composite Lumber (SCL) 1999
Result, bonded joints can be more efficient than other joining techniques such as mechanical fastening. Epoxies appear superior in terms of initial joint strength to other generic adhesive types. Joint optimisation is possible using FE. Inclusion of FRP rods can increase joint or beam strength. Guidelines being prepared for application of bonded-in connections.
IVF
MIXFOG hybrid joining of different materials in sheet and profile form developing design and rating data for combinations of materials (aluminium, carbon steel, stainless steel and polymers) and jointing methods (clinching, punch riveting, lock bolting, adhesive bonding/sealing, and combinations). Organisations involved: IVF, Adtranz, Volvo, Avesta Sheffield, SAPA, SSAB Tunn-plat, Swedish Institute for Metals Research, Swedish Corrosion Institute, the Royal Institute of Technology.
Lulea University project on adhesive bonding and weldbonding of stainless steel.
TWI
Internal Research: Assessment Procedures for Joints in Composite Structures to provide Confidence in Performance
Internal Research: Performance Predictions for Adhesively Bonded Joints
See also Oxford Brooke Dogma pages and register on the site http://www.twi.co.uk for direct access to the Weldasearch engine.
Westgate S A ‘Clinching and self-piercing riveting for sheet joining’ TWI report. This report covers the static performance and fatigue behaviour of a number of commercially available self-piercing riveting and clinching systems. Data have been generated for carbon steel, 5182 aluminium alloy and Al/PP/Al sandwich structure.
Westgate S A and Razmjoo G R ‘Static and fatigue performance of mechanically fastened and hybrid joints in sheet metal. TWI Report 691 December 1999.
Razmjoo G R and Westgate S A ‘Fatigue properties of clinched, self-pierced riveted and spot welded joints in steel and aluminium alloy sheet’ TWI Report 680/1999 July 1999
Hahn O, Peetz A ‘Improvement of the joint element properties through the combination of mechanical fasteners and adhesive bonding’ (IIW) Welding in the World vol. 43, no.3, May-June 1999 pp 38-46
Linder J and Melander A ‘Fatigue design data for new joining techniques and new materials’ Svetsaren vol. 53, no. 3, 1998, pp 6-9
Harris J A, Martin R H ‘Development of a life assessment method for bonded and weld bonded automotive structures’ SAE Paper 980692 Publ Warrendale, PA 15096, USA 1998
Ishii K, Imanaka M, Nakayama H, Kodama H ‘Fatigue failure criterion of adhesively bonded CFRP/metal joints under multi-axial stress conditions’ Composites vol. 29A, no.4, 1998 pp 415-422
Manteghi S, Abson D J ‘Some fatigue tests on adhesively bonded fibre reinforced metal laminates’ TWI Journal vol.6, no. 3, 1997 pp 417-453
Hejcman D, Knott J F, Bowen P, Davis C L ‘Fatigue of welded and adhesively bonded aluminium alloys for use in automotive applications’ ECF 11 Mechanisms and Mechanics of Damage and Failure Proc. 11th Biennial European Conference on Fracture ISBN 0-947817-93-X pp 1669-1670
ROY A., 1994, ENSMA Poitiers PhD thesis. Mechanical behaviour of bonded composite/composite and composite/metal joints under monotonic and cyclic loading partly presented in:
Roy A., Mabru C, Gacougnolle JL, Davies P. ‘Damage mechanisms in composite/composite bonded joints under static tensile loading’ Applied Composite Materials, 4, 1997, pp95-119
Roy A, Royer J, Davies P ‘Fatigue behaviour of marine composites’ Proc Int Conf on Fatigue of Composites Paris, June 3-5 1997 pp439-446
See also http://www.brookes.ac.uk/dogma and register on the site http://stella.grantapark.com/joinit_044/docs/homepage.html for direct access to the Weldasearch engine.
Further information on the DTI funded Performance of Adhesive Joints (PAJ) programme can be found at http://www.npl.co.uk/npl/cmmt/programmes/pajinfo.html
Dillard J, Grant W, Harp S, Holmer B, Wolfe K ‘ Surface preparation for adhesive bonding’ Pitture & Vernici vol. 73, no. 9, May 1997 pp 41-45
Wilson I, Shearby P G, Maddison A ‘The significance of environment for performance of structural adhesive bonding’ Book: Applications of Al in Vehicle Design SP-1251 Publ Warrendale, PA 15096, USA, SAE Paper 970012 pp 1-2
BSI ‘Adhesives durability of structural adhesive joints exposure to humidity and temperature under load’ BS ISO 14615:1997 ISBN 0-580-29179-0
McGrath G C ‘The durability of adhesively bonded joints in composite structures’ Composite Polymers 1991 4 (3) 189-198.
Gontcharova-Benard E., 1997 ENSMA Poitiers PhD thesis
Ageing of adhesively bonded steel/composite joints in water under load. Certain information presented in:
Roy A, E. Gontcharova-Bénard, J-L Gacougnolle, P. Davies ‘Hygrothermal effects on failure mechanisms in composite/steel bonded joints’ ASTM STP 1357, Time dependent & Non-linear effects in polymers and composites, 2000, pp 353-371.
The Handbook of Sandwich Construction Ed. D Zenkert ISBN 0 947817 96 4 (1997) 442 pages
Sandwich Construction 4 Proc. Of 4th Int. Conf. On Sandwich Construction Sweden 8-12 June 1998 Ed. K-A Olsson ISBN 1 901537 00 5 (1998) 902 pages in 2 volumes
For above, e-mail: info@emas.co.uk
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