Project 3 - Environmental durability
Objectives
- To evaluate existing procedures for durability assessment and to develop a test methodology.
- To establish a durability database of key adhesively bonded joints and joint types.
- To develop a non-destructive technique for monitoring moisture ingress.
- To evaluate bonded structures and establish performance and degradation mechanisms.
- To determine microstructural failure mechanisms.
- To develop life prediction methods.
Principal findings
- The test methods available at present are able to rank adhesive systems (i.e. adherend, surface and adhesive) in order of performance. A high degree of variability is seen however, and this leaves scope for test method development and interpretation of results.
- Although short term testing can be satisfactory for ranking, great care must be taken with the test piece geometry. For example, lap joints are very poor for high durability combinations and accelerated ageing tests are not appropriate for the evaluation of quantitative test data.
- Investigations of in-service structures have shown that adhesive bonding is successful and that joints are generally tolerant of flaws. The chemical stability of the adherends, however, is critical and oxidation or degradation needs to be avoided for maximum performance.
- Skilful manipulation of the product allows astute joint designs to be developed and should be considered along with surface preparation at the design stage, to prevent moisture ingress and improve manufacture.
- The design engineer is encouraged to seek guidance when using adhesives, as one cannot simply replace other joining techniques with an adhesively bonded joint. Joint design, surface preparation, assembly, etc. must be considered.
- Investigation of failure mechanisms usually reveals apparent interfacial failure, with water ingress being much greater than by simple diffusion, stressing the importance of the smart joint. Although the failure is apparently interfacial, a closer inspection generally reveals a very thin layer of adhesive remaining on the surface.
- Design methodology requires pragmatic skills to address the adhesive system. The tools that can be applied include: interpolation within data sets; correlations using calculated stress distributions and the use of fracture mechanics to provide estimates of fatigue limits.
| REPORTS | |||||
| REPORT NO. | REPORT TITLE | ABSTRACT | NO. PAGES | SIZE (MB) | LINK |
| 1 | Environmental Durability Test Procedures | Show | 153 | 12.04 |
|
| 2 | Evaluation of Published Durability Data | Show | 78 | 6.084 |
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| 3 | Sensing Techniques for Detection of Water in Adhesives | Show | 30 | 3.236 |
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| 4 | Property Measurememt of Bulk Adhesives | Show | 23 | 3.07 |
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| 5 | Predicting the Lifetime of Adhesive Joints in Hostile Environments | Show | 26 | 2.277 |
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| 6 | A Review of Industrial Case Histories | Show | 57 | 9.01 |
|
| 7 | Use of Neural Netwroks to Evaluate Adhesive Joint Durability Data | Show | 26 | 1.104 |
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| 8 | Experimental Assessment of Durability Test Methods | Show | 183 | 11.29 |
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| 9 Pt 1 | Forensic Studies of Adhesive Joints. Part 1 - General Introduction and Conclusion | Show | 34 | 2.078 |
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| 9 Pt 2 | Forensic Studies of Adhesive Joints. Part 2 - Bonded Aircraft Structure | Show | 62 | 1.749 |
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| 9 Pt 3 | Forensic Studies of Adhesive Joints. Part 3 - Foden Truck Door | Show | 38 | 2.756 |
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| 9 Pt 4 | Forensic Studies of Adhesive Joints. Part 4 - Footwear | Show | 18 | 1.866 |
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| 9 Pt 5 | Forensic Studies of Adhesive Joints. Part 5 - Law 80 Rocket Launcher | Show | 30 | 14.07 |
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| 9 Pt 6 | Forensic Studies of Adhesive Joints. Part 6 - Externally Bonded Steel Plate Reinforcement for Concrete Bridges | Show | 54 | 79.77 |
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| 9 Pt 7 | Forensic Studies of Adhesive Joints. Part 7 Aircraft Repairs | Show | 74 | 4.719 |
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| 9 Pt 8 | Forensic Studies of Adhesive Joints. Part - 8 Glass Fibre Reinforced Plasic Process Pipeline | Show | 29 | 19.99 |
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| 10 | Detection of Water Adsorption in Adhesive Joints | Show | 35 | 0.973 |
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| 11 | Locus of Failure of Bonded Joints | Show | 24 | 0.117 |
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| 12 | Finite element analysis of dry and wet butt lap joints | Show | 73 | 4.661 |
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| 13 | Durability and Lifetime Predictions of Adhesive Joints | Show | 73 | 3.605 |
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| 14 | Overall Summary | Show | 20 | 0.161 |
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