Abstract
A systematic experimental study was performed to detect the compaction and permeability properties of multilayered biaxial and quadriaxial preforms under vacuum pressure. Compression response on ply level showed that the degree of nesting between quadriaxial NCF was more pronounced and the nesting deformation mechanism was affected by the interaction with stitch yarns. Owing to the meso-channels in the fibrous structure and the nesting between layers, the in-plane permeability of quadriaxial NCF did not follow an inverse proportion relationship with the fiber volume fraction. To predict the in-plane permeability of multilayered quadriaxial NCFs, unit cell models at a high level of geometrical details were built, including local variations in yarn cross-sections and the nesting deformation between layers. Numerical methods were implemented, and the prediction results were in very good agreement with the experimental data. Besides, the major contributing parameters to the enhancement of the in-plane permeabilities were identified by investigating the correlation between permeability and structural parameters of quadriaxial NCF. The modeling methodology and the principles established can be applied to the design of the quadriaxial NCF fabrics, where the permeability enhancement was evidenced.
Highlights
Non-crimp fabrics (NCFs) are widely used as textile reinforcement for composite materials.NCFs are built up by layers of fiber bundles that are stitched together by warp-knitting loops in different directions through thickness
Since NCFs show better axial mechanical properties and have much higher production efficiency than other crimped textile reinforcements, NCFs are especially applied in liquid composite molding (LCM) processes as reinforcements for large and thick composite parts
The nesting is significant since the quadriaxial NCF has wider channels between tows, leaving enough space for the tows on the backside of the adjacent layer to nest inside the channel (Figure 1c–f)
Summary
Non-crimp fabrics (NCFs) are widely used as textile reinforcement for composite materials.NCFs are built up by layers of fiber bundles that are stitched together by warp-knitting loops in different directions through thickness. Non-crimp fabrics (NCFs) are widely used as textile reinforcement for composite materials. Since NCFs show better axial mechanical properties and have much higher production efficiency than other crimped textile reinforcements, NCFs are especially applied in liquid composite molding (LCM) processes as reinforcements for large and thick composite parts. LCM is a widely used technique for the manufacturing of composite parts with large sizes, complex shapes, short cycle time and low cost. It includes subclasses like resin transfer molding (RTM) and vacuum-assisted RTM (VARTM). LCM techniques have in common that a stack of fabric layers is placed into a mold and a liquid resin is subsequently driven through the textile reinforcement
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