Force attenuation performance in sandwich structures with STF and M-STF encapsulation

In this study, we investigate the role of adding shear thickening fluids (STFs) and multi-functional shear thickening fluids (M-STFs) to the core of a sandwich-structured composite made of aluminum facesheets and XPS foam cores with different geometries on force attenuation performance. Six different core designs were machined, and all designs had the same space for adding STFs and M-STFs. STF with 40 wt% SiO₂ in PEG 400 was selected and fabricated. M-STFs were made by adding multi-walled carbon nanotubes (MWCNTs) up to 1.5 wt%. The effects of MWCNTs on the rheological and electrical properties of the STF were investigated. The force attenuation tests were performed with an impact drop tower test system at three different heights with 5, 10, and 15 J energy levels. According to the results, V6_STF (with 16 holes with a diameter of 6 mm) and H6_STF (with 16 rectangular cubic column with cross-sections of 6 × 6 mm) designed sandwich structures showed better performance in terms of force attenuation compared with the other samples. Next, these two sandwich structures were filled again with M-STF (0.5 wt% MWCNT), and the force attenuation performance of the structures showed an improvement further, and the H6_STF_CNT sample improved by 24.8% compared to the clean sandwich structure sample. These results demonstrate the potential of STFs and M-STFs in strengthening the force attenuation performance of sandwich structures with XPS foam cores, mainly when used with appropriate core geometry.