Investigate the post-impact residual strengths of multi-walled carbon nanotube shear thickening fluid reinforced fibre metal laminates

This study aims to investigate the impact damage and residual strengths of fibre metal laminates (FMLs) reinforced with modified shear thickening fluid (STF) which is formed by mixing multi-walled carbon nanotube (MWCNT) and silicon nanoparticles with polyethylene glycol. MWCNT-STF was produced and impregnated to Kevlar fabric, which was then bonded to aluminium (Al) plates to form MWCNT-STF Kevlar fibre metal laminates (CK-FMLs) with a stacking sequence of 3/2 (Al/Kevlar/Al/Kevlar/Al). Firstly, CK-FMLs were subjected to low-velocity impact with an impact energy from 1 to 9 J to mimic damage during their service life caused by dropping tools or runway debris. Secondly, compression-after-impact (CAI) and tension-after-impact (TAI) tests were carried out to investigate their corresponding residual strengths. Then, various FMLs with stacking sequences of 2/1, 3/2 and 4/3 were subjected to perforation impact to evaluate their corresponding impact resistances and failure modes. The computer tomography (CT) scanning analysis shows that the internal damage volume ratios of CK-FMLs subjected to impact energy of 1, 3 and 5 J are decreased by 2.23, 3.16 and 5.64 % in comparison to the pure Kevlar (PK) FMLs (PK-FMLs) counterparts. Furthermore, the CAI and TAI residual strengths of CK-FMLs under the various pre-impact energies are increased by 6.03–19.98 % and 7.49–32.16 %, respectively, in comparison to their PK counterparts. The investigation also shows that the peak contact force of 4/3 CK-FMLs is enhanced by 170.59 % over its 2/1 counterpart. This study provides the firsthand database for the design of this novel impact-resistant materials, which will lead to new applications in aerospace and defense industry.