Proceedings of the Institution of Mechanical Engineers,Part L: Journal of Materials: Design and Applications

This work presents a methodology for correlating the mechanical properties determined by rheological measurements with the degree of cure that has been measured in differential scanning calorimetry. Therefore, a model-based as well as a model-free kinetic approach is used to calculate the degree of cure depending on the temperature profile the sample is submitted to during the rheological measurements. Afterwards the rheological data is related to this degree of cure. The combination of these different techniques of thermal analysis show good correlation and offer a deeper understanding of the development of the mechanical properties during cure.

A bonded ring test is proposed to study crack onset under pure and mixed mode conditions. In the existing centre-cracked Brazilian disc configuration, introduction of a central crack may be arbitrary and can easily lead to initial asymmetric crack configuration. Moreover, the crack front geometry is, in general, unknown which may result in serious consequences on crack onset and fracture parameters. In the present work, a bonded ring loaded in compression was investigated numerically and experimentally. Two bimaterial singular points were introduced between the half discs and the adhesive providing privileged crack onset location – controllable during specimen fabrication. Three types of specimens were analysed using digital image correlation and finite element techniques: homogenous poly(methyl methacrylate), bonded poly(methyl methacrylate) and bonded poly(methyl methacrylate) to stainless steel rings. A satisfying agreement between experimental and numerical approaches was found enabling more complex analysis in future. Such test configuration can be of interest for crack onset studies and estimation of fracture parameters under mixed mode I/II loading conditions.

This work presents electro-dry-adhesives, designed for use on conducting surfaces, that synergistically combine biomimetic dry adhesives with mushroom-like fibres and embedded conductive polymer electrodes. Together, the dry-adhesive surface and electrodes enable the electro-dry-adhesives to generate greatly improved shear adhesion bond strengths. The electro-dry-adhesives described in this work are fabricated with a poly(dimethylsiloxane) biomimetic dry-adhesive surface and embedded interdigitated electrodes manufactured from a carbon black and poly(dimethylsiloxane) composite conductive polymer. The poly(dimethylsiloxane) dry-adhesive layer allows the electro-dry-adhesives to be used both passively and actively, and the poly(dimethylsiloxane) acts as a dielectric insulator between the electrodes and enables the electro-dry-adhesive to be used on conducting surfaces. In order to compare both passive and active use of the electro-dry-adhesives, shear adhesion bond strength is measured and compared with voltage potentials from 0 kV up to 3 kV applied across the electrodes with up to a 2.56 times increase in shear adhesion bond strength. The increase in shear adhesion bond strength due to the generation of an induced electrostatic attractive force is compared to the theoretical maximum shear adhesion bond strength at each of the voltages applied.

In a previous research study, a protein from Bacillus subtilis was cloned in an overexpressing strain and produced in higher amounts than in natural conditions, with the aim of assessing whether this protein can be a candidate to be considered in the formulation of new biobased, bioinspired adhesives with industrial purposes. A bioadhesion assay, as well as the morphological analysis by scanning electron microscopy and confocal laser scanning microscopy, confirmed the involvement of the protein under study in the biofilm formation and adhesion processes of the bacterium. Furthermore, its suitability for being used as a polymeric base for adhesive formulations was assessed in terms of thermal properties, wettability of different substrates, surface tension, particle size distribution and bondability to polymeric adherends. The results obtained were promising. Nevertheless, it was found that the adhesive should be conveniently formulated in order to improve its performance. In this work, the purified protein has been modified using glutaraldehyde, which is commonly used in protein crosslinking. Structural changes produced in the protein, which could affect its suitable use as an adhesive, were assessed in terms of crystallinity, morphology, thermal properties and spectroscopic properties.

The design of polymers from renewable resources is subject to increasing interest, more specifically with regard to the development of biodegradable materials in order to reduce the dependence on petroleum and its negative impact on the environment. Thanks to the versatility of polyurethane adhesives, they can be formulated by designing their properties through the selection of their reagents. This work focused on the development of potentially biodegradable polyurethane adhesives containing polyols from renewable resources, such as soya-based vegetable oils. Moreover, they were synthesised with 1,4-butanediol as a chain extender and two diisocyanates were tested, an aromatic, 4,4′-diphenylmethane diisocyanate and an aliphatic, 1,6-hexamethylene diisocyanate, which is considered more biodegradable. The biodegradable polyurethane adhesives were characterised by Fourier transform infrared spectroscopy, thermogravimetric tests, differential scanning calorimetry and gel permeation chromatography. Finally, the adhesion properties were measured in a T-peel test on leather/polyurethane adhesive/styrene butadiene rubber joints, in order to establish the amount of soya bean oil-based polyol that could be added to synthesise polyurethane adhesives satisfactorily and meet the quality requirements for footwear.

Joining of components is usually accomplished by mechanical fastening, welding, or adhesive bonding. Apart from the classical methods, various hybrid methods applied with adhesives are widely used in industry to bond mechanical parts. This study describes a new hybrid bonding method as an alternative to currently used hybrid methods: adhesive-soft soldered joints. In this new hybrid technique, joints are made by adding various (5 wt%, 15 wt%, 25 wt%, and 50 wt%) amounts of soft soldering alloy powder into the adhesive at two different temperatures (180℃ and 200℃). The strength of the joints is measured by tensile shear tests. The mechanical strength of adhesive joints carried out by adding soft soldering powder melted at 200℃ is higher than that of joints with only adhesives and unmelted soft soldering powders. The developed hybrid method is applied to attach the insert to cutting tools used in the machining industry and the feasibility of the method is investigated with experiments.