Talat Lecture 4702: Factors Influencing The Strength Of Adhesive Joints
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TALAT Lecture 4702
Factors Influencing the Strength of Adhesive Joints 13 pages, 13 figures Basic Level prepared by Lutz Dorn, Technische Universität, Berlin
Objectives: − to describe the factors governing the strength of adhesive joints in order to appreciate these factors for the design of adhesively bonded joints, i.e. geometry of joint, stiffness and strength of the adjoining parts, stress distribution in the adhesive layer as well as the effects of humidity and ageing
Prerequisites: − general background in production engineering and material science − background in mechanics and polymer science
Date of Issue: 1994 EAA - European Aluminium Association
4702 Factors Influencing the Strength of Adhesive Joints
Table of Contents 4702 Factors Influencing the Strength of Adhesive Joints ........................2 4702.01 Basic Factors Governing Strength of Joints.......................................... 3 Interdependence of material and design factors.......................................................3 Loading factors ........................................................................................................3 Summary of influencing parameters ........................................................................4 4702.02 Stress Distributions in Lap Joints .......................................................... 5 Load distribution in adhesive sheet joints................................................................5 Stress distribution in a brittle and an elastic-plastic adhesive layer.........................5 Distribution of stress during peeling........................................................................6 4702.03 Effects of Geometric Parameters............................................................. 7 Influence of overlapping on adhesive joints ............................................................7 Correlation of overlap length and joining part elongation.......................................7 4702.04 Effects of Stiffness and Strength of the Joining Parts .......................... 8 Correlation between adhesive strength and joining part thickness ..........................8 Correlation between adhesive strength and strength of joint parts ..........................9 4702.05 Effects of Ageing under Stress and Humidity ....................................... 9 Behaviour of aluminium alloy 6060 - T6 under stressing........................................9 4702.06 Fatigue Behaviour of Adhesive Joints................................................... 10 Deformation behaviour of adhesive layers under repeated stress ..........................10 Correlation between fatigue strength under repeated stress and a number of cycles for different strengths of joining parts ...................................................................11 4702.07 Literature/References ............................................................................. 12 4702.08 List of Figures............................................................................................ 13
TALAT 4702
2
4702.01 Basic Factors Governing Strength of Joints • • •
Interdependence of material and design factors Loading factors Summary of influencing parameters
Interdependence of material and design factors The peculiar behaviour of the strength of adhesively joint metals is a result of the fact that the joint system is not homogeneous but consists instead of a composite system in which the resulting properties are a combination of the individual properties of the parts to be joint, the adhesive layer and the interface layers (Figure 4702.01.01).
Strength of Adhesive Metal Joints Adhesive Layer
Surface Joining Materials
Adhesive
Adhesive Joint
Strength of Adhesive Joint
Geometric Design
Optimally Constructed Joint
Stressing
Source: Habenicht alu
Factors Influencing the Strength of Adhesive Joints
Training in Aluminium Application Technologies
4702.01.01
The specific properties of the adhesive joint are a result of the strengths obtained due to the geometrical and material design. The following statement can serve as a basis for assessing the behaviour of adhesive joints in metals and consequently in dimensioning and designing such joints. Loading factors The overall performance of an adhesive metal joint is characterised by the measure in which it is able to withstand loads without any appreciable change in its original strength values (Figure 4702.01.02)
TALAT 4702
3
S t r e s s in g T y p e
Mechanical Stress: Shear Tension Tensile-Shear Bending (Peeling) Compression Torsion
Environmental Stress: (Aging) Complex Stress: (Both Types)
Temperature (Reaction)
Physical
Climate gen. Corrosive Climate
Chemical
Time-Dependent Stress
Long-Time Short-Time
Static Reversed Repeated
Impact, High-Rate Impat
Static Dynamic
Static Source: Habenicht alu
Types of Stresses on Adhesive Joints
4702.01.02
Training in Aluminium Application Technologies
Summary of influencing parameters The combined action of the influencing factors and their parameters are the basis for the production of an optimal adhesive joint and govern its attainable strength (Figure 4702.01.03).
Strength of Adhesively Joined Metals Adhesive Layer
Joining Material
Modulus of
Modulus of
Elasticity, EK
Elasticity, EF
Shear Modulus, G
Geometric Design
Stress Type
Overlap Length, lü
Mechanical
Overlap Width b
Physical
Joining Part Thickness, s
Chemical
Adhesive Layer Thickness, d
Complex Mech., Phy., Chem., Time-Dependent
Tensile Strength, Rm
Poisson´s Ratio, µK
Yield Strength,
Stress-Shearing-
0.2 % Offset Yield
Behaviour
Strength, Rp0,2
Re
Poisson´s Contraction
Source: Habenicht alu Training in Aluminium Application Technologies
TALAT 4702
Parameters Influencing the Strength of Adhesive Joints in Metals
4
4702.01.03
4702.02 Stress Distributions in Lap Joints • • •
Load distribution in adhesive sheet joints Stress distribution in a brittle and an elastic-plastic adhesive layer Distribution of stress during peeling
Load distribution in adhesive sheet joints The load distribution in one-sided lap joints subjected to tensile-shear loading, depends on the stiffness of the joint parts and the deformability of the adhesive layer. The amount of the relative movement of the joint parts is a result of the deformation capacity of the adhesive layer (Figure 4702.02.01).
Stress Distribution in Adhesive Sheet Joints τα
Unloaded Joint
A
σα
B
C
D
Loaded Rigid Joint and Shear Stress Distribution
Loaded Unrigid Joint and Normal Stress Distribution alu
Stress Distribution in Adhesive Sheet Joint
4702.02.01
Training in Aluminium Application Technologies
Stress distribution in a brittle and an elastic-plastic adhesive layer Adhesives of the elastic-plastic type cause only low stress peaks at the overlap ends, in spite of the large relative movements of the joint parts (Figure 4702.02.02).
TALAT 4702
5
Stress of Adhesive Joints in Metals
τmax
a)
b)
τmax
F
F
F
F v2
v1
v1 < v2
Stress Distribution in a Brittle (a) and an Elastic - Plastic (b) Adhesive Layer
alu Training in Aluminium Application Technologies
4702.02.02
Distribution of stress during peeling The occurrence of possible peeling stress during loading has a very major influence on the strength of adhesive joints. They occur both in tensile tests conducted on lap joints (due to eccentric loading) as well as in pure peeling tests (with extremely high stress peaks) (Figure 4702.02.03).
Stress of Adhesive Joints in Metals F X
X
σmax
alu
Distribution of Stress during Peeling
Training in Aluminium Application Technologies
TALAT 4702
6
4702.02.03
4702.03 Effects of Geometric Parameters • •
Influence of overlapping on adhesive joints Correlation of overlap length and joining part elongation
Influence of overlapping on adhesive joints The strength of narrow (≤ 5 mm) overlapped joints is a result of solely adhesion and cohesion forces in the adhesive layer. At overlapping lengths exceeding a certain amount and depending on the geometry and strength of the joint parts and on the deformation capacity of the adhesive layer, stress peaks, in excess of the strength of the adhesive layer, occur at the overlap ends causing the strength to fall (Figure 4702.03.01).
Strength of Adhesive Joints in Metals 80
Adhesive Strength τ B
Adhesive Strength τ B
Nmm -2 60
1 2 3
40 20
0
5
10 15 20 25 30 35 40 45 50 mm Length of Overlap lü
1 = Epoxy Dicynanoamide 2 = Phenolic Polyvinyl Formal 3 = PMMA - Neoprene / Styrene
Length of Overlap lü Influence of Overlap Length on Adhesive Strength ( schematic )
Adhesive Strength as a Function of Overlap Length in Adhesive Joints with Different Deformation Behaviours Source: Matting alu
Influence of Overlapping on Adhesive Joints
4702.03.01
Training in Aluminium Application Technologies
Structural materials should not be subjected to stresses exceeding their proportionality limit. In practice, the limiting stress should be lower than the 0.2 % yield strength. Correlation of overlap length and joining part elongation Consequently, the optimal overlapping length, lo2, of adhesive joints is so chosen that overloading the structural to more than the limiting stress causes a rupture of the adhesive layer (Figure 4702.03.02).
TALAT 4702
7
Strength of Adhesive Joints in Metals τ Bmax
τ Bm
τ Bmax
τ Bm
τ Bm
F
F
F
F
l ü1
F
l ü2
l ü3
F
σ R p 0,2
l ü1
alu Training in Aluminium Application Technologies
l ü2
l ü3
lü
Correlation of Overlap Length and Joining Part Elongation
4702.03.02
4702.04 Effects of Stiffness and Strength of the Joining Parts • •
Correlation between adhesive strength and joining part thickness Correlation between adhesive strength and strength of joint parts
Correlation between adhesive strength and joining part thickness The joint part thickness increases the strength of the adhesive joint by increasing both the stiffness as well as the bending moment of the joint. An increased thickness of the joint parts also increases the adhesive joint strength (Figure 4702.04.01). Stress peaks occurring at the overlap ends are lower for thicker joint parts because the latter leads to a higher rigidity allowing the adhesive layer to accommodate a larger part of the load.
TALAT 4702
8
Strength of Adhesive Joints in Metals 60 Nmm -2
1
Adhesive Strength τ B
45 2 3 30 1 = Epoxy Dicynanoamide 2 = Phenolic Polyvinyl Formal 3 = PMMA - Neoprene / Styrene 15
0
1,5
3
4,5
mm
6
Thickness of Joint, s Source: Brockmann
Correlation of Adhesive Strength and Joint Thickness
alu Training in Aluminium Application Technologies
4702.04.01
Correlation between adhesive strength and strength of joint parts These remarks apply in a similar manner to the strength of the joint components (Figure 4702.04.02).
Strength of Adhesive Metal Joints Examples for One-Sided Overlap Joints in Different Aluminium Alloys 40
Adhesive Joint Strength TB
[Nmm-2]
AlCuMg2 31
30 AlMg3 23
20 s = 10 mm
Al 12
lÜ = 7.0 mm
Adhesive EPOXY RESIN
10
110
0
100
230
200
480
300
400 [Nmm-2] 500
Tensile Strength Rm Source: Krekeler, Litz alu Training in Aluminium App lication Technologies
Correlation Between Adhesive Strength and Joining Parts Strength; Examples
4702.04.02
4702.05 Effects of Ageing under Stress and Humidity •
Behaviour of aluminium alloy 6060 - T6 under stressing
Behaviour of aluminium alloy 6060 - T6 under stressing The strength of an adhesive joint depends on the thermal and mechanical stress as well as on the humidity of the environment.
TALAT 4702
9
The combined occurrence of both types of stresses is especially harmful (Figure 4702.05.01).
Strength of Adhesive Metal Joints a)
b) 28 Phenolic Resins, warm hardening
14,0 Nmm -2 10,5
21 14 Epoxy Resins, cold hardening
Stress σ
Adhesive Joint Strengtht τ B
Nmm -2
3,5
7 0
Phenolic Resins, warm hardening
7,0
Epoxy Resins, cold hardening 100
500 300 Stressing Time
700 days
10
Behaviour of Aluminium Alloy 6060 - T6 under Stressing: a) 52° C, 100 % rel. Humidity, without Mechanical Stressing
10 2 10 3 10 4 10 5 min 7 days 70 Time to Failure of Joint
b) 52° C, 100 % rel. Humidity, with Mechanical Stressing Source: Minford alu Training in Aluminium Application Technologies
Behaviour of Aluminium Alloy 6060 - T6 under Stressing
4702.05.01
4702.06 Fatigue Behaviour of Adhesive Joints • •
Deformation behaviour of adhesive layers under repeated stress Correlation between fatigue strength under repeated stress and a number of cycles for different strengths of joining parts
Deformation behaviour of adhesive layers under repeated stress Adhesive joints with sufficient deformation capacity have a longer operational life than those with lower deformability. Fatigue strength increases with the static strength of the adhesive. At 107 cycles, the fatigue strength is equal to about 14 % of the static short-time strength (Figure 4702.06.01).
TALAT 4702
10
Strength of Adhesive Metal Joints 18 Nmm-2 14
1
1 = Epoxy - Nylon 2 = Epoxy - Polyaminoamide 3 = Phenolic - Polyvinyl Formal
Maximum Stress
!0
12 2 10 9 3 8
7.2
7
!B = 50 Nmm-2 ! 2 - B = 43.4 Nmm-2 3 - !B = 37.4 Nmm-2 1-
6 5 104
5
105
6.1 5.7
5 106 Number of Cycles
5 N
107
5
108
Source: Matting, Draugelates
Deformation Behaviour of Adhesive Layers under Repeated Stress
alu Training in Aluminium Application Technologies
4702.06.01
Correlation between fatigue strength under repeated stress and a number of cycles for different strengths of joining parts High-strength materials, adhesively joint, attain higher life-cycles under dynamic loading due to the slight deformation of the adhesive layer. This means that the stress peaks are lower and the load distribution is more favourable (Figure 4702.06.02).
Strength of Adhesive Metal Joints 15
Repeated Stress Tschw
[Nmm-2]
Adhesive: Epoxid - Phenol
10 X 10 CrNiNb 18 9
AlCuMg 2 pl 5
0 103
104
105
106
107
108
Number of Cycles N
Source: Althof
alu Training in Aluminium Application Technologies
TALAT 4702
Correlation Between Fatigue Strength and Number of Cycles for Different Strength of Joining Parts
11
4702.06.02
4702.07 Literature/References 1. Habenicht, G.: Kleben. Springer-Verlag Berlin-Heidelberg-New York 1990. 2. Crocombe, A.D. and Adams, R.D.: Influence of the spew fillet and other parameters on the stress distribution in the single lap joint. J.of Adhesion 13 (1981), pp. 141-155 3. Dorn, L. and Liu, W.: The stress state and failure properties of adhesive-bonded plastics/metal joints. Int. J. Adhesion and Adhesives Vol. 13 (1993), No.1, pp. 21-31 4. Adams, R.D. , Coppendale, V., Mallick, Al-Hamdan, H.: The effect of temperature on the strength of adhesive joints. Int. J. Adhesion and Adhesives Vol. 12 (1992), No.3, pp.185-190 5. Bigwood, D.A. and A.D. Crocombe: Non-linear adhesive bonded joint design analyses. Int. J. Adhesion and Adhesives Vol. 10 (1990), No.1, pp. 31-41 6. Minford, J.D.: Adhesives. In: Durability of Structural Adhesives, Applied Science Publishers, New York and London 1983, pp. 135-214 7. Matting, A. und Draugelates, U.: Die Schwingfestigkeit von Metallklebverbindungen. Adhäsion 12 (1968), H. 1, S. 5-22; H. 3, S. 110-134, H. 4, S. 161-176. 8. Eichhorn, F. und Stockhausen, G.: Langzeit- und Alterungsverhalten hochwertiger Schmelzklebverbindungen von Metallen. AIF-Abschlußbericht Nr. 5234, Aachen 1984. 9. Hahn, O. und Wender, B.: Beanspruchungsanalyse von geometrisch und werkstoffmechanisch „unsymmetrischen“ Metallklebverbindungen mit der FiniteElemente-Methode. Forschungsbericht des Landes NRW, Nr. 3187. Westdeutscher Verlag, Opladen 1984. 10. Brockmann, W.: Grundlagen und Stand der Metallklebtechnik. VDI-Verlag, Düsseldorf 1971. 11. Matz, C.: Klärung der adhäsiven Bindungsmechanismen von strukturellen Aluminium-Klebverbindungen. Forschungsbericht (LFF 8350 6) des BMFT, 1985 12. Brockmann, W., Hennemann, O.-D., Kollek, H. und Matz, C.: Adhäsion in Aluminiumklebungen des Flugzeugbaus. Adhäsion 30 (1986) H. 7/8, S. 31-38; H. 9, S. 24-35; H.10, S. 20-35. 13. Althof, W.: Festigkeit von Metallklebverbindungen Beanspruchung. DFBO-Mitt. 19 (1968) 5, S. 48-51.
TALAT 4702
12
bei
schwingender
4702.08 List of Figures
Figure No.
Figure Title (Overhead)
4702.01.01 4702.01.02 4702.01.03
Factors Influencing the Strength of Adhesive Joints Types of Stresses on Adhesive Joints Parameters Influencing the Strength of Adhesive Joints in Metals
4702.02.01 4702.02.02 4702.02.03
Stress Distribution in Adhesive Sheet Joints Stress Distribution in a Brittle (a) and an Elastic-Plastic (b) Adhesive Layer Chemical Reacting Adhesives
4702.03.01 4702.03.02
Influence of Overlapping on Adhesive Joints Correlation of Overlap Length and Joining Part Elongation
4702.04.01 4702.04.02
Correlation of Adhesive Strength and Joint Part Thickness Correlation between Adhesive Strength and Joining Parts Strength; Examples
4702.05.01
Behaviour of Aluminium Alloy 6060 - T6 under Stressing
4702.06.01 4702.06.02
Deformation Behaviour of Adhesive Layers under Repeated Stress Correlation Between Fatigue Strength and Number of Cycles for Different Strengths of Joining Parts
TALAT 4702
13
Factors Influencing the Strength of Adhesive Joints 13 pages, 13 figures Basic Level prepared by Lutz Dorn, Technische Universität, Berlin
Objectives: − to describe the factors governing the strength of adhesive joints in order to appreciate these factors for the design of adhesively bonded joints, i.e. geometry of joint, stiffness and strength of the adjoining parts, stress distribution in the adhesive layer as well as the effects of humidity and ageing
Prerequisites: − general background in production engineering and material science − background in mechanics and polymer science
Date of Issue: 1994 EAA - European Aluminium Association
4702 Factors Influencing the Strength of Adhesive Joints
Table of Contents 4702 Factors Influencing the Strength of Adhesive Joints ........................2 4702.01 Basic Factors Governing Strength of Joints.......................................... 3 Interdependence of material and design factors.......................................................3 Loading factors ........................................................................................................3 Summary of influencing parameters ........................................................................4 4702.02 Stress Distributions in Lap Joints .......................................................... 5 Load distribution in adhesive sheet joints................................................................5 Stress distribution in a brittle and an elastic-plastic adhesive layer.........................5 Distribution of stress during peeling........................................................................6 4702.03 Effects of Geometric Parameters............................................................. 7 Influence of overlapping on adhesive joints ............................................................7 Correlation of overlap length and joining part elongation.......................................7 4702.04 Effects of Stiffness and Strength of the Joining Parts .......................... 8 Correlation between adhesive strength and joining part thickness ..........................8 Correlation between adhesive strength and strength of joint parts ..........................9 4702.05 Effects of Ageing under Stress and Humidity ....................................... 9 Behaviour of aluminium alloy 6060 - T6 under stressing........................................9 4702.06 Fatigue Behaviour of Adhesive Joints................................................... 10 Deformation behaviour of adhesive layers under repeated stress ..........................10 Correlation between fatigue strength under repeated stress and a number of cycles for different strengths of joining parts ...................................................................11 4702.07 Literature/References ............................................................................. 12 4702.08 List of Figures............................................................................................ 13
TALAT 4702
2
4702.01 Basic Factors Governing Strength of Joints • • •
Interdependence of material and design factors Loading factors Summary of influencing parameters
Interdependence of material and design factors The peculiar behaviour of the strength of adhesively joint metals is a result of the fact that the joint system is not homogeneous but consists instead of a composite system in which the resulting properties are a combination of the individual properties of the parts to be joint, the adhesive layer and the interface layers (Figure 4702.01.01).
Strength of Adhesive Metal Joints Adhesive Layer
Surface Joining Materials
Adhesive
Adhesive Joint
Strength of Adhesive Joint
Geometric Design
Optimally Constructed Joint
Stressing
Source: Habenicht alu
Factors Influencing the Strength of Adhesive Joints
Training in Aluminium Application Technologies
4702.01.01
The specific properties of the adhesive joint are a result of the strengths obtained due to the geometrical and material design. The following statement can serve as a basis for assessing the behaviour of adhesive joints in metals and consequently in dimensioning and designing such joints. Loading factors The overall performance of an adhesive metal joint is characterised by the measure in which it is able to withstand loads without any appreciable change in its original strength values (Figure 4702.01.02)
TALAT 4702
3
S t r e s s in g T y p e
Mechanical Stress: Shear Tension Tensile-Shear Bending (Peeling) Compression Torsion
Environmental Stress: (Aging) Complex Stress: (Both Types)
Temperature (Reaction)
Physical
Climate gen. Corrosive Climate
Chemical
Time-Dependent Stress
Long-Time Short-Time
Static Reversed Repeated
Impact, High-Rate Impat
Static Dynamic
Static Source: Habenicht alu
Types of Stresses on Adhesive Joints
4702.01.02
Training in Aluminium Application Technologies
Summary of influencing parameters The combined action of the influencing factors and their parameters are the basis for the production of an optimal adhesive joint and govern its attainable strength (Figure 4702.01.03).
Strength of Adhesively Joined Metals Adhesive Layer
Joining Material
Modulus of
Modulus of
Elasticity, EK
Elasticity, EF
Shear Modulus, G
Geometric Design
Stress Type
Overlap Length, lü
Mechanical
Overlap Width b
Physical
Joining Part Thickness, s
Chemical
Adhesive Layer Thickness, d
Complex Mech., Phy., Chem., Time-Dependent
Tensile Strength, Rm
Poisson´s Ratio, µK
Yield Strength,
Stress-Shearing-
0.2 % Offset Yield
Behaviour
Strength, Rp0,2
Re
Poisson´s Contraction
Source: Habenicht alu Training in Aluminium Application Technologies
TALAT 4702
Parameters Influencing the Strength of Adhesive Joints in Metals
4
4702.01.03
4702.02 Stress Distributions in Lap Joints • • •
Load distribution in adhesive sheet joints Stress distribution in a brittle and an elastic-plastic adhesive layer Distribution of stress during peeling
Load distribution in adhesive sheet joints The load distribution in one-sided lap joints subjected to tensile-shear loading, depends on the stiffness of the joint parts and the deformability of the adhesive layer. The amount of the relative movement of the joint parts is a result of the deformation capacity of the adhesive layer (Figure 4702.02.01).
Stress Distribution in Adhesive Sheet Joints τα
Unloaded Joint
A
σα
B
C
D
Loaded Rigid Joint and Shear Stress Distribution
Loaded Unrigid Joint and Normal Stress Distribution alu
Stress Distribution in Adhesive Sheet Joint
4702.02.01
Training in Aluminium Application Technologies
Stress distribution in a brittle and an elastic-plastic adhesive layer Adhesives of the elastic-plastic type cause only low stress peaks at the overlap ends, in spite of the large relative movements of the joint parts (Figure 4702.02.02).
TALAT 4702
5
Stress of Adhesive Joints in Metals
τmax
a)
b)
τmax
F
F
F
F v2
v1
v1 < v2
Stress Distribution in a Brittle (a) and an Elastic - Plastic (b) Adhesive Layer
alu Training in Aluminium Application Technologies
4702.02.02
Distribution of stress during peeling The occurrence of possible peeling stress during loading has a very major influence on the strength of adhesive joints. They occur both in tensile tests conducted on lap joints (due to eccentric loading) as well as in pure peeling tests (with extremely high stress peaks) (Figure 4702.02.03).
Stress of Adhesive Joints in Metals F X
X
σmax
alu
Distribution of Stress during Peeling
Training in Aluminium Application Technologies
TALAT 4702
6
4702.02.03
4702.03 Effects of Geometric Parameters • •
Influence of overlapping on adhesive joints Correlation of overlap length and joining part elongation
Influence of overlapping on adhesive joints The strength of narrow (≤ 5 mm) overlapped joints is a result of solely adhesion and cohesion forces in the adhesive layer. At overlapping lengths exceeding a certain amount and depending on the geometry and strength of the joint parts and on the deformation capacity of the adhesive layer, stress peaks, in excess of the strength of the adhesive layer, occur at the overlap ends causing the strength to fall (Figure 4702.03.01).
Strength of Adhesive Joints in Metals 80
Adhesive Strength τ B
Adhesive Strength τ B
Nmm -2 60
1 2 3
40 20
0
5
10 15 20 25 30 35 40 45 50 mm Length of Overlap lü
1 = Epoxy Dicynanoamide 2 = Phenolic Polyvinyl Formal 3 = PMMA - Neoprene / Styrene
Length of Overlap lü Influence of Overlap Length on Adhesive Strength ( schematic )
Adhesive Strength as a Function of Overlap Length in Adhesive Joints with Different Deformation Behaviours Source: Matting alu
Influence of Overlapping on Adhesive Joints
4702.03.01
Training in Aluminium Application Technologies
Structural materials should not be subjected to stresses exceeding their proportionality limit. In practice, the limiting stress should be lower than the 0.2 % yield strength. Correlation of overlap length and joining part elongation Consequently, the optimal overlapping length, lo2, of adhesive joints is so chosen that overloading the structural to more than the limiting stress causes a rupture of the adhesive layer (Figure 4702.03.02).
TALAT 4702
7
Strength of Adhesive Joints in Metals τ Bmax
τ Bm
τ Bmax
τ Bm
τ Bm
F
F
F
F
l ü1
F
l ü2
l ü3
F
σ R p 0,2
l ü1
alu Training in Aluminium Application Technologies
l ü2
l ü3
lü
Correlation of Overlap Length and Joining Part Elongation
4702.03.02
4702.04 Effects of Stiffness and Strength of the Joining Parts • •
Correlation between adhesive strength and joining part thickness Correlation between adhesive strength and strength of joint parts
Correlation between adhesive strength and joining part thickness The joint part thickness increases the strength of the adhesive joint by increasing both the stiffness as well as the bending moment of the joint. An increased thickness of the joint parts also increases the adhesive joint strength (Figure 4702.04.01). Stress peaks occurring at the overlap ends are lower for thicker joint parts because the latter leads to a higher rigidity allowing the adhesive layer to accommodate a larger part of the load.
TALAT 4702
8
Strength of Adhesive Joints in Metals 60 Nmm -2
1
Adhesive Strength τ B
45 2 3 30 1 = Epoxy Dicynanoamide 2 = Phenolic Polyvinyl Formal 3 = PMMA - Neoprene / Styrene 15
0
1,5
3
4,5
mm
6
Thickness of Joint, s Source: Brockmann
Correlation of Adhesive Strength and Joint Thickness
alu Training in Aluminium Application Technologies
4702.04.01
Correlation between adhesive strength and strength of joint parts These remarks apply in a similar manner to the strength of the joint components (Figure 4702.04.02).
Strength of Adhesive Metal Joints Examples for One-Sided Overlap Joints in Different Aluminium Alloys 40
Adhesive Joint Strength TB
[Nmm-2]
AlCuMg2 31
30 AlMg3 23
20 s = 10 mm
Al 12
lÜ = 7.0 mm
Adhesive EPOXY RESIN
10
110
0
100
230
200
480
300
400 [Nmm-2] 500
Tensile Strength Rm Source: Krekeler, Litz alu Training in Aluminium App lication Technologies
Correlation Between Adhesive Strength and Joining Parts Strength; Examples
4702.04.02
4702.05 Effects of Ageing under Stress and Humidity •
Behaviour of aluminium alloy 6060 - T6 under stressing
Behaviour of aluminium alloy 6060 - T6 under stressing The strength of an adhesive joint depends on the thermal and mechanical stress as well as on the humidity of the environment.
TALAT 4702
9
The combined occurrence of both types of stresses is especially harmful (Figure 4702.05.01).
Strength of Adhesive Metal Joints a)
b) 28 Phenolic Resins, warm hardening
14,0 Nmm -2 10,5
21 14 Epoxy Resins, cold hardening
Stress σ
Adhesive Joint Strengtht τ B
Nmm -2
3,5
7 0
Phenolic Resins, warm hardening
7,0
Epoxy Resins, cold hardening 100
500 300 Stressing Time
700 days
10
Behaviour of Aluminium Alloy 6060 - T6 under Stressing: a) 52° C, 100 % rel. Humidity, without Mechanical Stressing
10 2 10 3 10 4 10 5 min 7 days 70 Time to Failure of Joint
b) 52° C, 100 % rel. Humidity, with Mechanical Stressing Source: Minford alu Training in Aluminium Application Technologies
Behaviour of Aluminium Alloy 6060 - T6 under Stressing
4702.05.01
4702.06 Fatigue Behaviour of Adhesive Joints • •
Deformation behaviour of adhesive layers under repeated stress Correlation between fatigue strength under repeated stress and a number of cycles for different strengths of joining parts
Deformation behaviour of adhesive layers under repeated stress Adhesive joints with sufficient deformation capacity have a longer operational life than those with lower deformability. Fatigue strength increases with the static strength of the adhesive. At 107 cycles, the fatigue strength is equal to about 14 % of the static short-time strength (Figure 4702.06.01).
TALAT 4702
10
Strength of Adhesive Metal Joints 18 Nmm-2 14
1
1 = Epoxy - Nylon 2 = Epoxy - Polyaminoamide 3 = Phenolic - Polyvinyl Formal
Maximum Stress
!0
12 2 10 9 3 8
7.2
7
!B = 50 Nmm-2 ! 2 - B = 43.4 Nmm-2 3 - !B = 37.4 Nmm-2 1-
6 5 104
5
105
6.1 5.7
5 106 Number of Cycles
5 N
107
5
108
Source: Matting, Draugelates
Deformation Behaviour of Adhesive Layers under Repeated Stress
alu Training in Aluminium Application Technologies
4702.06.01
Correlation between fatigue strength under repeated stress and a number of cycles for different strengths of joining parts High-strength materials, adhesively joint, attain higher life-cycles under dynamic loading due to the slight deformation of the adhesive layer. This means that the stress peaks are lower and the load distribution is more favourable (Figure 4702.06.02).
Strength of Adhesive Metal Joints 15
Repeated Stress Tschw
[Nmm-2]
Adhesive: Epoxid - Phenol
10 X 10 CrNiNb 18 9
AlCuMg 2 pl 5
0 103
104
105
106
107
108
Number of Cycles N
Source: Althof
alu Training in Aluminium Application Technologies
TALAT 4702
Correlation Between Fatigue Strength and Number of Cycles for Different Strength of Joining Parts
11
4702.06.02
4702.07 Literature/References 1. Habenicht, G.: Kleben. Springer-Verlag Berlin-Heidelberg-New York 1990. 2. Crocombe, A.D. and Adams, R.D.: Influence of the spew fillet and other parameters on the stress distribution in the single lap joint. J.of Adhesion 13 (1981), pp. 141-155 3. Dorn, L. and Liu, W.: The stress state and failure properties of adhesive-bonded plastics/metal joints. Int. J. Adhesion and Adhesives Vol. 13 (1993), No.1, pp. 21-31 4. Adams, R.D. , Coppendale, V., Mallick, Al-Hamdan, H.: The effect of temperature on the strength of adhesive joints. Int. J. Adhesion and Adhesives Vol. 12 (1992), No.3, pp.185-190 5. Bigwood, D.A. and A.D. Crocombe: Non-linear adhesive bonded joint design analyses. Int. J. Adhesion and Adhesives Vol. 10 (1990), No.1, pp. 31-41 6. Minford, J.D.: Adhesives. In: Durability of Structural Adhesives, Applied Science Publishers, New York and London 1983, pp. 135-214 7. Matting, A. und Draugelates, U.: Die Schwingfestigkeit von Metallklebverbindungen. Adhäsion 12 (1968), H. 1, S. 5-22; H. 3, S. 110-134, H. 4, S. 161-176. 8. Eichhorn, F. und Stockhausen, G.: Langzeit- und Alterungsverhalten hochwertiger Schmelzklebverbindungen von Metallen. AIF-Abschlußbericht Nr. 5234, Aachen 1984. 9. Hahn, O. und Wender, B.: Beanspruchungsanalyse von geometrisch und werkstoffmechanisch „unsymmetrischen“ Metallklebverbindungen mit der FiniteElemente-Methode. Forschungsbericht des Landes NRW, Nr. 3187. Westdeutscher Verlag, Opladen 1984. 10. Brockmann, W.: Grundlagen und Stand der Metallklebtechnik. VDI-Verlag, Düsseldorf 1971. 11. Matz, C.: Klärung der adhäsiven Bindungsmechanismen von strukturellen Aluminium-Klebverbindungen. Forschungsbericht (LFF 8350 6) des BMFT, 1985 12. Brockmann, W., Hennemann, O.-D., Kollek, H. und Matz, C.: Adhäsion in Aluminiumklebungen des Flugzeugbaus. Adhäsion 30 (1986) H. 7/8, S. 31-38; H. 9, S. 24-35; H.10, S. 20-35. 13. Althof, W.: Festigkeit von Metallklebverbindungen Beanspruchung. DFBO-Mitt. 19 (1968) 5, S. 48-51.
TALAT 4702
12
bei
schwingender
4702.08 List of Figures
Figure No.
Figure Title (Overhead)
4702.01.01 4702.01.02 4702.01.03
Factors Influencing the Strength of Adhesive Joints Types of Stresses on Adhesive Joints Parameters Influencing the Strength of Adhesive Joints in Metals
4702.02.01 4702.02.02 4702.02.03
Stress Distribution in Adhesive Sheet Joints Stress Distribution in a Brittle (a) and an Elastic-Plastic (b) Adhesive Layer Chemical Reacting Adhesives
4702.03.01 4702.03.02
Influence of Overlapping on Adhesive Joints Correlation of Overlap Length and Joining Part Elongation
4702.04.01 4702.04.02
Correlation of Adhesive Strength and Joint Part Thickness Correlation between Adhesive Strength and Joining Parts Strength; Examples
4702.05.01
Behaviour of Aluminium Alloy 6060 - T6 under Stressing
4702.06.01 4702.06.02
Deformation Behaviour of Adhesive Layers under Repeated Stress Correlation Between Fatigue Strength and Number of Cycles for Different Strengths of Joining Parts
TALAT 4702
13
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