The modelling of friction in polymer fibre ropes

Polymer fibre ropes are assemblies of in some cases half a million polymer fibres; this can in some circumstances be considered a ‘continuum’. However, the detail of these components results in a structure which is both inhomogeneous and anisotropic; the consideration of inhomogeneity is necessary since each component is distinct and there is no continuity of motion between them and anisotropy is the result of twist and braiding various subcomponents {yarns, strands, subropes} into a further component. aper discusses the analysis of rope structures; it will survey the hierarchical approach in which the base component {fibres, filaments} are developed into a structure {yarns, plies}. This structure is then a component which forms the basis for the next higher structure, {strands, subropes, multiplies}. The progress in analysis and indeed in fabrication through the rope structure thus leads quite naturally to the hierarchical approach where the top is the rope and the bottom is the base yarn, the fibre or indeed for wire ropes, the wire. The assumptions used pertain to the detail of the contact between contiguous components; these are within a hierarchical level and pertain to contact within a layer or between layers; the contact friction must inhibit component sliding and the assumption of a friction force-contact force law must be made. Friction is identified in six modes: linear sliding, twist slip, sawing and scissoring between components and distortion and dilation within components. The effects of inter and intra friction are discussed and thus integrated into the analysis and model. aper will first survey the various rope constructions. Then it will describe the analysis for rope deformations and loads which will yield also the loads and deformations of the internal components. Finally this paper will survey the mechanisms of component slip and show the analysis for the various friction modes.