Effect of phosphorylation on the planar compaction of reinforcements made of unidirectional flax fibres supported by a thin flax fibre mat

Transverse compaction of fibre reinforcements has significant importance in the production of complex dry fibre preforms for the resin transfer moulding (RTM) process of composite materials. This work investigates, for the first time, the planar compaction of phosphorylated stacks of unidirectional (UD) reinforcements made of flax yarns held together by a thin layer of short flax fibres. Planar compaction tests were carried out to evaluate the influence of temperature and humidity on the creep percentage, thickness recovery, and permanent deformation of UD reinforcements prepared with and without phosphorylation. It appears that the creep percentage and permanent deformation are more important for phosphorylated reinforcements than for untreated ones. Increasing the compaction temperature and humidity results in an increase of the creep and permanent deformation of phosphorylated fibres. The tensile strength of phosphorylated fibres-reinforced composites is lower than that of untreated ones while there is no effect on the tensile modulus.