The structural hierarchy of fibrillar ultra-high molecular weight poly
ethylene (UHMW-PE) fibres is investigated and related to fibre mechani
cal properties. Chemical etching has been used to change the surface p
roperties of these UHMW-PE fibres through the removal of a skin layer
and UHMW-PE oxidation. The physical and chemical changes to the fibre
surface introduced by etching affect single-fibre mechanical propertie
s. The effects of etchant and etching time on failure properties and m
echanisms is discussed. The decrease in failure strain and strength wi
th etching is associated with the change from an energy-absorbing fibr
il delamination failure to brittle fracture.