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Friction and adhesion properties between fibres is of great importance as it affects both the physical and mechanical performance of end products made from these fibres. Thus, the aimed of this thesis is to understand the fundamental knowledge of the friction and adhesion behaviour between single fibres focusing on aramid fibre type. An experimental setup for measuring the friction and adhesion between single fibres is developed. Since the contribution of the surface physical properties is one of the important factors influencing the friction and adhesion, the wetting and surface energy of single aramid fibre is studied using Wilhelmy’s method. Result shows that the surface energy of aramid fibres is polar in character, exhibiting hydrophilic behaviour. The influence of the parameters such as pre-tension load, fibre orientation, normal load and elastic modulus on the friction force is studied. Taut wire model is used to formulate the contact length between contacting fibre surfaces in perpendicular contact. Using this model, the deflection of the fibre as well as the contact intimacy between fibres can be calculated and related to the measured friction force. However, it is found that the ‘wrapping effect’ due to pre-tension is small in comparison with the elastic deformation in contact. In an elliptical contact, it is found the role of pre-tension is relatively small and friction and contact area between fibres are dominated by the effect of fibre orientation. Generally the friction force decreases as the crossing angle increases and the Hertzian elliptical contact model is used to explain this phenomenon. At constant crossing angle, the adhesion force shows a significant increase at relative humidity of 50%. At very low humidity levels (~8%), the adhesion force is reducing with increasing crossing angle. The contribution of the contact area due to the crossing angle effect is assessed using the JKR elliptical adhesive contact model. The experimental data fits with the model by considering the roughness effect as a scaling factor. In conclusion, friction and adhesion between single aramid fibres have been explored successfully. Studies found that the role of the contact area between two contacting fibres is important in influencing the friction and adhesion force values.

An experimental study of friction and adhesion between single aramid fibres