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The use of carbon fibres is being explored in synchronous belts due to their excellent mechanical properties, chemical and dimensional stability. However, poor adhesion between fibres and the common rubber-fibre adhesive resorcinol-formaldehyde-latex (RFL) compromises load transfer between these constituents. We examined the influence of surface characteristics of commercial glass and carbon fibres, such as fibre surface chemistry, energy and area on carbon fibre-RFL matrix adhesion in model single fibre composites. Fibres with higher surface oxygen content and thus more polar functional groups resulting in a higher surface energy exhibited better adhesion to RFL. Fibre adhesion behaviour to RFL can be ranked using the aspect ratio of the fibre diameter to the critical fragment length as assessed by single fibre fragmentation tests, however, accurate interfacial shear strength values cannot be obtained using the Kelly-Tyson model due to statistical limitations in the treatment of single fibre tensile properties. Our results provide insight into factors affecting fibre-RFL adhesion and identified commercial T700GC-31E carbon fibres as candidates for improved fibre-matrix adhesion for the production of more robust synchronous belts. [ABSTRACT FROM AUTHOR]

A continuous atmospheric plasma (AP) polymerisation method was developed, using an acrylonitrile precursor, to enhance the adhesion of carbon fibres to an elastomeric resorcinol formaldehyde latex (RFL) matrix. Different processing speeds, corresponding to different residence times in the afterglow zone of the plasma jet, and precursor dosing rates were explored to optimise the treatment. X-ray photoelectron spectroscopy showed that carbon fibres were successfully functionalised in this process. The higher hydrophilicity and better adhesion to RFL was mainly attributed to the introduction of polar amide and hydroxyl groups introduced onto carbon fibre surfaces. Single fibre tensile tests confirmed that AP treatment did not affect the bulk mechanical properties of carbon fibres. The adhesion behaviour between carbon fibres and RFL was characterised by single fibre fragmentation tests. The interfacial shear strength, as measure of practical adhesion, increased by 30% for the fibres exposed longest to the plasma. The plasma-treated carbon fibres were aged in ambient atmosphere for up to three months to determine the effect of storage on the adhesion between the fibres and RFL. After ageing, an 11% reduction of interfacial shear strength was observed. [ABSTRACT FROM PUBLISHER]