Ja Poulis

UV/ozone cleaning, a convenient alternative for high quality bonding preparation

Abstract Optimal adhesive bonding necessitates good and reproducible cleaning. A cleaning method based on the interaction of ultraviolet light and ozone gas has been developed and used. The uv /ozone cleaning method is compared with soap cleaning, and with advanced gas plasma cleaning, the cleaning efficiency being characterized by spectroscopic data and contact angle measurements. The (short- and long-term) influence of these cleaning methods on the long-term adhesive bond strength has been determined experimentally and is discussed.

Lap Shear and Impact Testing of Ochre and Beeswax in Experimental Middle Stone Age Compound Adhesives.

The production of compound adhesives using disparate ingredients is seen as some of the best evidence of advanced cognition outside of the use of symbolism. Previous field and laboratory testing of adhesives has shown the complexities involved in creating an effective Middle Stone Age glue using Acacia gum. However, it is currently unclear how efficient different adhesive recipes are, how much specific ingredients influence their performance, and how difficult it may have been for those ingredients to be combined to maximum effect. We conducted a series of laboratory-based lap shear and impact tests, following modern adhesion testing standards, to determine the efficacy of compound adhesives, with particular regard to the ingredient ratios. We tested rosin (colophony) and gum adhesives, containing additives of beeswax and ochre in varying ratios. During both lap shear and impact tests compound rosin adhesives performed better than single component rosin adhesives, and pure acacia gum was the strongest. The large difference in performance between each base adhesive and the significant changes in performance that occur due to relatively small changes in ingredient ratios lend further support to the notion that high levels of skill and knowledge were required to consistently produce the most effective adhesives.

Improvements in bonding metals (steel, aluminium)

Abstract: This chapter discusses the developments in materials, processes and design, which make adhesive bonding an efficient and durable joining technology for metal structures. The chapter reviews the developments in adhesives and surface treatments for metal bonded joints, which have improved the mechanical properties and processing characteristics as well as significantly enhanced durability under humid or corrosive environments. Next developments in joint design are discussed, from simple lap joints to complex bonded metal laminates. Further improvements in modelling and testing techniques are reviewed, which have led to more accurate prediction and determination of joint strength and durability.

Improvements in bonding metals for aerospace and other applications

Abstract: This chapter discusses the developments in materials, processes and design, which make adhesive bonding an efficient and durable joining technology for metal structures. The chapter reviews the developments in adhesives and surface treatments for metal-bonded joints, which have improved the mechanical properties and processing characteristics, as well as significantly enhanced durability under humid or corrosive environments. Developments in joint design are discussed, from simple lap joints to complex bonded metal laminates. Further improvements in modelling and testing techniques are reviewed, which have led to more accurate prediction and determination of joint strength and durability.

The use of acoustic emission and composite peel tests to detect weak adhesion in composite structures

ABSTRACT Adhesive bonding is one of the most promising joining technologies for composite aircraft. However, to comply with current aircraft certification rules, current safety-critical bonded joints, in which at least one of the interfaces requires additional surface preparation, are always used in combination with redundant mechanical fasteners, such as rivets and bolts. This lack of trust in bonded structures is mostly linked to the fear of lack of adhesion or a “weak bond”. The aim of this paper is to tackle this challenge by assessing the ability to use composite peel tests and acoustic emission (AE) technique to assess adhesion quality and distinguish a good bond quality from a “weak bond”. Composite Bell Peel (CBP) tests and Double-Cantilever-Beam (DCB) tests were performed on contaminated and non-contaminated CFRP bonded specimens. The results show that peel strength drops significantly at the location of the contaminated interface that has led to weak adhesion, as a result from adhesive failure. The AE signals obtained during DCB tests show different features for cracks growing at the interface (“weak bonds”) and inside the adhesive layer (cohesive failure). In addition to this, scattering of the AE signals were observed in the contaminated specimens with “weak bonds”.