Method of fabricating an article by fused filament fabrication

A method of fabricating an article by fused filament fabrication, the method comprising:

• providing a FFF filament comprising a first set of reinforcement fibres, including a first reinforcement fibre, surrounded, at least in part, with a first polymeric composition;
• forming a first discontinuity of a first set of discontinuities in the first reinforcement fibre;
• and
• depositing the filament, including the first discontinuity of the first set of discontinuities formed in the first reinforcement fibre, comprising softening, at least in part, the first polymeric composition and solidifying the softened first polymeric composition;
• wherein depositing the filament, including the first discontinuity of the first set of discontinuities formed in the first reinforcement fibre, comprises depositing the filament, including the first discontinuity of the first set of discontinuities formed in the first reinforcement fibre, in a first arc of a set of arcs;
• wherein the first discontinuity of the first set of discontinuities in the first reinforcement fibre is a partial discontinuity at which the cross sectional area and/or diameter of the first reinforcement fibre is reduced by a percentage that is in a range from 10% to 90%;
• and
• wherein the method comprises surrounding the first set of reinforcement fibres, at least in part, with the first polymeric composition after forming the first discontinuity of the first set of discontinuities in the first reinforcement fibre.