Improving mechanical properties and ballistic limit of polyurethane foam cores in sandwich panels through multi-walled carbon nanotube reinforcement

This study investigates the effects of incorporating Multi-Walled Carbon Nanotubes (MWCNTs) into Polyurethane Foam (PUF) on the mechanical properties and impact performance of Aluminium and PUF sandwich panels. PUF samples with varying MWCNT weight fractions (0.1 wt.%, 0.2 wt.%, and 0.3 wt.%) were prepared and tested through compression, three-point bend, and impact testing. The addition of MWCNTs significantly improved the yield stress and compressive modulus of the PU foam core, with increases of up to 32.4% and 31.7%, respectively, for the highest MWCNT concentration. Three-point bend tests showed enhanced failure loads and core shear strength, with the highest load increase observed in the panels with 0.3 wt.% MWCNTs. Low velocity impact tests revealed no substantial improvement in the impact resistance with the addition of MWCNTs, as the aluminium face sheets primarily absorbed the impact energy. However, high velocity impact tests demonstrated improved energy absorption and reduced residual velocities for panels with MWCNTs, with a maximum ballistic limit velocity increase of 21.5% for the 0.3 wt.% MWCNT panels. CT scan analysis indicated that while the fundamental failure mechanisms remained consistent, the addition of MWCNTs improved the energy dissipation capabilities of the foam core. This study concludes that addition of MWCNTs in PUF may enhance the mechanical and ballistic performance of PU foam cores in sandwich panels, making them more effective in energy absorption without altering the core failure modes significantly.