Compaction, nesting and image based permeability analysis of multi-layer dry preforms by computed tomography (CT)

Textile preforms have a multi-scale hierarchy of fibres, tows and plies; geometry at each scale influences the manufacturing processes, the permeability of the textile to resin as well as the mechanical properties of the finished laminate. High-fidelity structural models for textile composites require accurate non-idealised tow geometry as well as changes to this geometry during processing. This paper presents a CT-based experimental technique for capturing the realistic meso-scale geometry of individual tows in a 2D fabric layer and the nesting or ply shifting between fabric layers in a multi-layer stack during a simulated consolidation process. An in-situ compression loading mechanism has been implemented in order to capture multi-layer preform geometry. Inter-tow and inter-ply void geometry has been captured in 3D due to high x-ray contrast between the fibres and the air. The degree of ply nesting and the connectivity between adjacent voids have been assessed at each stage of the compaction process. An image-based flow analysis has been performed on the extracted 3D realistic void geometry and the effect of layer nesting on resin flow has been evaluated. Image-based prediction of permeability values have been in good agreement with experimental values found in the literature when normalised as a function of fibre volume fractions.

Automated summary

This paper presents a CT-based experimental technique for capturing the realistic meso-scale geometry of individual tows in textile composites and assessing the effect of ply nesting on resin flow. The image-based prediction of permeability values has shown good agreement with experimental values found in the literature when normalized as a function of fiber volume fractions.