The Influence of Through-the-Thickness Binder Yarn Count on Fibre Volume Fraction, Crimp and Damage Tolerance within 3D Woven Carbon Fibre Composites

This paper presents a study into the influence of the Through-The-Thickness (T-T-T) binder yarn count on the fibre volume fraction (V _f ), crimp and damage tolerance within 3D woven carbon fibre composites. Three fabrics were woven with varying binder yarn counts; the first had 1x12k binders, the second had 2x6k binders (two individual 6k tows laid on top of one another into the structure to form one tow) and the third had 1x6k binder tows. Dry fabric compress tests conducted on the three 3D woven fabrics showed that a power law can be successful utilised to predict V _f and identify the required pressure to achieve a specific V _f . All three fabrics achieved V _f ‘s in the range of 45–47% however the 2x6k binder fabric had higher %CV's compared to the other fabrics. The degree of crimp within the three 3D woven fabrics was shown to be highest within the 1x12k binder fabric followed by the 1x6k binder fabric with the 2x6k binder fabric having the lowest percentage crimp. Compression after Impact (CAI) tests were conducted and showed that impact depth was significantly influenced by impact location on the T-T-T binders with impact depth differences up to 97% observed. It was shown that impact location and depth played no major role in the CAI strength of the composite. CAI strength was observed to be highest within the 2x6 k binder composite followed by the 1x6k binder composite with the 1x12k composite having the lowest CAI values.