Compaction behaviour of various flax fabric structures during composite manufacturing: mechanical characterisation and microstructural analysis

Flax fibre reinforced composites are becoming popular in the automotive and civil industries due to their environmentally friendly nature in terms of production and recycling and for their good specific strength. Textile structures undergo transverse compaction during composite manufacturing which changes the fabric thickness and ultimately fibre volume fraction of composites. Here, different flax fibre structures were investigated for compaction behaviour during composite forming to study the thickness changes of these fabrics under pressures between 1 and 10 bars. A range of composite manufacturing processes including vacuum infusion, autoclave curing and resin transfer moulding were utilised. These fabrics were studied in single and multi layer states, in dry and wet states, under different loading cycles and in different orientations of the fabric plies (00/00 and 00/900). Nesting of the layers has been calculated for single plies and for multi-layer stacks of dry fabrics. It was observed that under transverse compression, the structure of the preform plays a vital role in determining the thickness of the preform. The compressibility pattern of these various structures was also dissimilar for single layer and multi-layer stack which was attributed to the different nesting behaviours of these flax fibre structures.