The effects of compaction and interleaving on through-thickness electrical resistance and in-plane mechanical properties for CFRP laminates

The electrical conductivity of carbon fibre reinforced polymer (CFRP) laminates has previously been shown to be significantly improved by using different electrically functionalized interleaves - Functional Interleave Technology (FIT), particularly in through-thickness direction. Here, the mechanism of FIT is explored via the influence of compaction and interleaving of nickel plated polyester non-woven veils (NPVs) on through-thickness electrical conductivity and in-plane mechanical properties for the CFRP laminates are investigated. The through-thickness electrical property is found to be dominated by the electrically conductive network elements (carbon fibres) and components (carbon fibre layers and NPV layers), which, in turn, is strongly affected by compaction. By using the highly conductive NPVs, the through-thickness resistivity for cured FIT laminates was consistently lowered from 9.3 Ω⋅m to 0.48 Ω m and 1.54 Ω⋅m to 0.016 Ω m for 56% and 64% carbon fibre volume fraction laminates, respectively. The conductive mechanism of FIT specimens follows the series-resistor model, providing the potential to predict the through-thickness electrical conductivity (TTEC) value by interleaving the desired number of NPV layers. Investigation of in-plane mechanical properties indicates the flexural properties and interlaminar shear strength (ILSS) are less affected by compaction. Meanwhile, a 20% reduction of ILSS for FIT laminates is detected because of the lower intra-ply shear resistance of NPV layers.