7. Contact Force and Friction

This chapter introduces contact forces and pressures and its modelling; consequent to this is friction as occurs within the structure and between the constituent components. Various friction or more correctly energy dissipative mechanisms are identified and are grouped into two categories; those that arise because of relative motion between components are labelled INTER modes and those that arise because of the deformation of the component are INTRA modes and dilation and distortion are in the latter category. Because of the inhomogeneous nature of the fibre structures continuum theories do not necessarily lead to the best models. The quantification of dilation and distortion is achieved through the packing factor and the shape factor. Also included in this chapter is the modelling of structure life as limited by the continued abrasion between components. This uses the friction models and various wear criteria which must be measured by testing.