Murat Aydin

Aramid fabrics impregnated with shear thickening fluids (STFs) have significant potential for enhancing flexible ballistic protection systems. This study experimentally and statistically investigated the effects of carrier fluid, SiO ₂ particle size, and STF concentration on the ballistic performance of STF‐impregnated aramid fabrics. Eight STF formulations were prepared using polyethylene glycol (PEG 400) and dipropylene glycol (DPG) as carrier fluids, SiO ₂ particle sizes of 15–35 nm and 300 nm, and STF concentrations of 55% and 65%. Ballistic tests were conducted using a single‐stage gas gun, and the energy absorption results were evaluated using a 2 ³ full factorial experimental design and analysis of variance (ANOVA). All STF‐impregnated samples exhibited higher energy absorption than neat aramid fabric. The highest energy absorption, 257.16 J, was achieved by STF 1B/Aramid containing PEG 400, 15–35 nm SiO ₂ , and 65% STF. ANOVA revealed that particle size had the greatest contribution to energy absorption (35.74%), followed by STF concentration (21.38%) and carrier fluid (17.19%). The carrier fluid–particle size interaction was also statistically significant ( p < 0.05). Overall, smaller SiO ₂ particles (15–35 nm) provided superior ballistic energy absorption compared with 300 nm particles.

In this study, self-piercing riveting (SPR) connection, which is one of the joining techniques of aluminum alloys, is investigated. SPR is a cold mechanical joining process used to join two or more sheets of material by pushing the rivet that pierces the upper sheet under the guidance of a suitable mold and then locking it to the lower sheet. The SPR process was carried out with the split Hopkinson pressure par test system. The bar inside the cylinder, accelerated by pressure, performs the riveting process by hitting the surface of the mold developed for SPR. In this study, different numbers of slots were opened on the rivet tail, and the process was carried out using SPRs at different deformation rates. A powerful tomography scanner device designed for 3D metrology was used to visualise the SPR joining mechanisms without cutting. Tensile-shear tests were applied to the samples made with rivets with different numbers of slots and different pressures, and cross-tension tests were also applied to the samples prepared with rivets with different numbers of slots. The opened slots caused a decrease in the maximum strength of the samples. It was understood that the appropriate riveting pressure could change the connection strength by approximately 50%. In general, the force values decreased as the number of slots increased.

This study presents STF/Fabric composite configurations by impregnating single‐phase shear thickening fluids (S‐STF) and multi‐phase shear thickening fluids (M‐STF) into aramid fabrics. S‐STFs were first prepared at different concentrations by weight (25%, 40%, 55%, and 65%). In addition, M‐STFs were produced by adding silicon carbide (SiC) additive to S‐STFs. As a result of the impregnation of the produced STFs on Aramid fabrics, 30‐layer composite samples were prepared. To determine the ballistic performance of the produced samples, tests were carried out with a single‐stage gas gun system. The shots were performed at an average velocity of 670 m/s. Ballistic tests show that STF‐impregnated fabric samples have better ballistic performance compared to fabric without STF. The STF65/Aramid sample is notable for a 238% increase in energy absorption. In addition, the STF40SiC10/Aramid composite sample produced with M‐STF was found to absorb 18.7% more energy compared to the STF40/Aramid sample. It has been confirmed that keeping the weight ratio of the additive at an optimum level will contribute to ballistic performance. These results contributed to determining the optimum concentration amount for STF/Aramid composites at high speed.Highlights: S‐STF and SiC additive M‐STFs were produced. STFs were impregnated into 30‐layer Aramid fabrics. Ballistics tests were performed on S‐STF/Aramid and M‐STF/Aramid composite samples with a single‐stage gas gun system. The effects of S‐STF and M‐STF on ballistic performance were investigated. The addition of STF enhanced ballistic performance by increasing energy absorption.