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Surface Treatment Increases the Maximum Strain of PBO Fibres

20 December 2010

A multidisciplinary research team of IMDEA Materials Institute has developed a nitrogen plasma surface treatment to improve the mechanical behaviour of PBO fibres under axial compression.

PBO fibres are highly anisotropic polymeric fibres used in high-performance structural applications. The anisotropic fibre structure, which is responsible for the excellent tensile properties, makes PBO fibres relatively weak under axial compression, and their compressive strength is one order of magnitude lower than the tensile one.

Failure under axial compression is triggered at low strains by the initiation of a kink band from the surface by fibril microbuckling which propagates rapidly through the fibre cross-section to form a knuckle. Under further compressive or tensile deformation, the strain is localized in the knuckle leading to a considerable reduction of the fibre tensile strength. This mechanism limits the application of PBO fibres in structural components subjected to both tensile and compressive stresses or when axial compressive loads may appear during service.

The new surface treatment leads to a dramatic improvement (of the order of 40%) in the compressive strain for knuckle formation with a negligible effect on the tensile strength. This improvement opens a wide range of new possibilities for the use PBO fibres in advanced composite materials, ballistic protection textiles, structural cables, etc.

This technological innovation comes out from a R&D project (FUTURE PBO), partially funded by the Spanish Ministry of Science and Innovation, in which IMDEA Materials Institute collaborated with Future Fibres Rigging Systems S.L.U.