Talat Lecture 4703: Design And Calculation Of Adhesive Joints

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TALAT Lecture 4703

Adhesive Joints Design and Calculation 9 pages, 10 figures Basic Level prepared by Lutz Dorn, Technische Universität, Berlin

Objectives: − to describe the basic types of loadings of adhesive joints and to give examples of recommended joint designs − to calculate the strength of adhesive joints

Prerequisites: − general background in production engineering and material science − background in mechanics and polymer science

Date of Issue: 1994  EAA - European Aluminium Association

4703 Design and Calculation of Adhesive Joints Table of Contents 4703 Design and Calculation of Adhesive Joints ............................................2 4703.01 Design Recommendations for Adhesive Joints....................................... 2 Basic Types of Loadings of Adhesive Joint Geometries .........................................2 Examples for Joint Designs .....................................................................................4 4703.02 Calculation of Adhesive Joint Strength .................................................. 6 4703.03 Application Examples............................................................................... 7 4703.04 Literature/ References .............................................................................. 8 4703.05 List of Figures.............................................................................................. 9

4703.01 Design Recommendations for Adhesive Joints • •

Basic types of loadings of adhesive joint geometries Examples for joint designs: − Design of corner joints − Design of hollow section joints − Design of tube joints

Basic Types of Loadings of Adhesive Joint Geometries

Just as in the case of welding, the adhesive joint has to be specially optimised for adhesive joining in order to have a joint of optimal strength. Of the possible loading types which an adhesive joint can be subjected to, it is most suited for shear, torsion and compressive loads. Tensile and in particular cleavage or peeling forces should be avoided (Figure 4703.01.01).

TALAT 4703

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Design of Adhesive Metal Joints F

F F F

Tension Tensile - Shear

F

F

Cleavage

Peeling M M

F

t

t

Torsion

alu

Types of Stressing for Adhesive Joint Geometries

4703.01.01

Training in Aluminium Application Technologies

Design types which avoid peeling stresses in adesive ints of metals are illustrated in Figure 4703.01.02.

Design of Adhesive Metal Joints Peeling Stress

Mechanical Reinforcement of a Joint Part End by :

Additional Riveting / Screwing

Folding

Increasing Rigidity

Increasing Area

alu

Possibilities of Reducing Peeling Stress

4703.01.02

Training in Aluminium Application Technologies

Besides the most widely used (one-sided) lap joints shown in Figure 4701.01.01, Figure 4703.01.03 illustrates further possible designs for constructing overlapping adhesive joints. Scarf joints are most suitable for tensile-shear loading since the load distribution is favourable. These joints can, however, be used only for large joint part thicknesses and are complicated to manufacture TALAT 4703

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Design of Adhesive Metal Joints Double Lap

Joggle Lap

b

A=2 xb

A=xb

b x

x

Single-Sided Strapped Bevelled Single-Sided Lap A=xb/2

b

A=xb

b

x x

Double-Sided Strapped Scarf A=xb

b

b x

x

A=xb/cos(α)

α

Designing Overlapped Adhesive Joints alu

Designing Adhesive Lap Joints

4703.01.03

Training in Aluminium Application Technologies

Examples for Joint Designs Designs which have proved most successful for corner joints, closed-sectioned profile joints and tube joints are illustrated in Figure 4703.01.04, Figure 4703.01.05, and Figure 4703.01.06. While joining tubes of different coefficients of thermal expansion adhesively, the tube with the larger expansion should be designed to be on the outside.

Design of Adhesive Metal Joints

Corner Joints (Examples) alu

Examples for Joint Designs: Corner Joints

Training in Aluminium Application Technologies

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4703.01.04

Design of Adhesive Metal Joints

Closed Profiles (Examples) Examples for Joint Designs: Closed Profiles

alu

4703.01.05

Training in Aluminium Application Technologies

Design of Adhesive Metal Joints

Tube Joints (Examples) alu

Examples for Joint Designs: Tube Joints

Training in Aluminium Application Technologies

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4703.01.06

4703.02 Calculation of Adhesive Joint Strength Figure 4703.02.01 shows a rough method of calculating the strength of a single-sided lap joint based on a simplified form of the Volker equation according to Schliekelmann.

Calculation of Adhesive Joints The Mean Tensile-Shear Stress at Failure of Adhesive τB m is:

τB m = K ⋅ M ⋅ f

where the Adhesive Factor is:

K = τ B max ⋅

2d G

τB max = max. Tensile-Shear Stress at Failure of Adhesive Joint d = Adhesive Layer Thickness G = Shear Modulus and the Metal Factor is:

M= E E = Modulus of Elasticity of Joint Material

and the Design Factor is:

f=

s lü

s = Joint Thickness lü = Overlap Length This results in the Following Final Equation for the Mean Tensile-Shear Stress:

τ B m = τ B max ⋅

alu

Calculation of Adhesive Joints

2Esd 2 Glü

4703.02.01

Training in Aluminium Application Technologies

Depending on the application, it is necessary to choose the appropriate safety factor as well as a number of design and load-dependent reducing factors.

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4703.03 Application Examples Typical application examples for adhesively joint metal constructions are layered or laminated, shell and sandwich constructions Figure 4703.03.01, Figure 4703.03.02, and Figure 4703.03.03. Sandwich constructions are only possible with adhesive joining.

Practical Examples

Laminated Constructions alu

Example of Joints: Laminated Construction

4703.03.01

Training in Aluminium Application Technologies

Practical Examples

Shell Constructions

alu

Example of Joints: Shell Construction

Training in Aluminium Application Technologies

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4703.03.02

Practical Examples

Corrugated Sheet

Balsa Cross-Cut Wood

Supported Core Sandwich Constructions

alu Training in Aluminium Application Technologies

Examples of Joints: Supported Core Sandwich Constructions

4703.03.03

Other applications where adhesive joints are being successfully used are, for example, shaft-hub joints, screw-locking, sealing, in combination with other joining methods i.e., spot welding, riveting or folding.

4703.04 Literature/ References 1. Schliekelmann, R.J.: Klebtechnische Erfahrungen aus dem Flug- und Raumfahrzeugbau. Zeitschriften für Schweißtechnik (Schweiz) 16 (1966), H. 8, S. 319-327. 2. Schliekelmann, R.J.: Metallkleben - Konstruktion und Fertigung in der Praxis. DVS Verlag Düsseldorf, 1972. 3. Adam, R. and Wake, W.: Structural adhesive joints in engineering. Elsevier Applied Science Publishers London and New York 1984. 4. Hart-Smith, L.J.: Designing adhesive bonds. Akhesives Age 21 (1978) 10, S. 3237. 5. Hart-Smith, L.J.: Further developments in the design and analysis of adhesivebonded structural joints. ASTM STP 749, ed by K.T. Kedward, American Society for Testing and Materials 1980, pp-3-31.

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6. Dorn, L. und Salem, N.: Klebgerechtes Gestalten von Kunststoff-MetallKlebverbindungen. Maschinenmarkt Würzburg 99 (1993) Nr. 35, S. 66-72. 7. Schlimmer, M.: Formulierung des Klebstoffverhaltens im Zugscherversuch mit Berücksichtigung der Schädigung. Schweißen und Schneiden 38 (1986) H. 11, S. 545-550. 8. Kinloch, A.J. and Smart, N.R.: Bonding and failure mechanisms in aluminium alloy adhesive joints. Journal of Adhesion 12 (1981), pp. 23-35.

4703.05 List of Figures

Figure No. 4703.01.01 4703.01.02 4703.01.03 4703.01.04 4703.01.05 4703.01.06

Figure Title (Overhead) Types of Stressing for Adhesive Joint Geometries Possibilities of Reducing Peeling Stress Designing Adhesive Lap Joints Examples for Joint Designs: Corner Joints Examples for Joint Designs: Closed Profiles Examples for Joint Designs: Tube Joints

4703.02.01

Calculation of Adhesive Joints

4703.03.01 4703.03.02 4703.03.03

Example of Joints: Laminated Construction Example of Joints: Shell Construction Example of Joints: Supported Core Sandwich Constructions

TALAT 4703

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