Abstract:

Objective In the general trend of the development of flexible protective equipment, people have higher and higher requirements for protective clothing, flexible puncture-proof material requiring protective materials to be able to simultaneously achieve light weight, good protective effect, and to enhance comfort. High-performance fiber materials are lightweight and textile processable. However, when multiple layers of textiles are stacked up to achieve puncture-proof performance, the final product materials show heavyweight and poor wearing comfort. While high-performance fabric composites effectively improve the puncture resistance, this study aims to improve the puncture resistance of high-performance fabric composites and to investigate the application of composites.

Method Multiphase shear thickening fluids (MSTFs) were prepared by dispersing monodisperse phase SiO₂ particles in polyethylene glycol (PEG) 200 and adding multi-walled carbon nanotubes (MWCNTs). The shear thickening solution was stored under open exposure, sealed exposure and sealed from light, and the ageing properties of the shear thickening solution were investigated based on the rheological properties. After that, the aramid fabric was impregnated with MSTFs (S), and multilayer composites with different stack structures were prepared by combining silicon carbide/polyurethane (SiC/TPU) coated aramid fabric (T) and untreated aramid fabric (N), and quasi-static stapling and dynamic knife-puncture behaviors were investigated.

Results The study investigated the effect of interfacial interaction on the puncture resistance of the composites. It was found that the critical shear rate of MSTFs with the addition of multi-walled carbon nanotubes decreased, the maximum thickening viscosity was increased, and the thickening effect was improved. In this circumstance, the rheological properties of the shear-thickened solution under open exposure storage conditions were decreased more in a short period of time and were easily affected by air humidity. Due to the better water absorption of PEG, indicating decreased number of hydrogen bonds between PEG and silica and after moisture absorption, the viscosity of the system was decreased, and the interaction force between the particles was enhanced, hence not easy to produce more particle clusters. Regression analysis was performed with storage time as the variable thickening rate as the dependent variable, and it showed that y_STF=31.695xSTF-0.278 and y_MSTFs=29.115xMSTFs-0.262, with a strong correlation between the variables. In addition, from the results of quasi-static nail testing, it was clear that the three-layer composite prepared by shear-thickening solution impregnating aramid fabric (S) + pure aramid fabric (N) + coated aramid fabric (T) laminate structure exhibited the best puncture resistance, and the SSNNTT laminate structure illustrated better puncture-proof performance than the six-layer composite with SNTSNT laminate structure. Due to the friction between long spike and MSTFs-impregnated fabrics increased, and the MSTFs composite fabric can be bonded with pure fabric to more tightly to limit the slip of pure fabric yarns and fibers, which driving more yarns to resist puncture. Therefore, when the long nails wrapped around the fabric pierced the coated fabric, it need for greater puncture force to pierce the coated fabric, the number of yarn and fiber breaks at the puncture opening increased, the anti-puncture performance is improved. while in SSNNTT laminated structure, the friction between double-layer MSTFs composite and long spike is greater, and the sandwiched pure fabric has more yarns involved in the puncture process, thus absorbing more puncture energy. According to the change curve of impact force and impact energy corresponding to the puncture process. The dynamic puncture performance of the composites is consistent with their performance in static puncture resistance behavior, with the 5S5N5T(S N T with 5layers each) structural composites providing the best knife puncture resistance. During the piercing of the tool, the impact force of the instant composite material punctured by the knife tip reaches the maximum, and the impact energy of the tool is rapidly reduced at this time. So the consumption of impact energy by puncture-resistant materials is mainly concentrated in the puncture process before the impact force reaches its maximum value, and it shows that the impact energy of multi-layer composite decreases more than that of the tool before the material is punctured, which exhibits better anti-stabbing performance. From the duration of the energy begins to drop to the minimum impact energy, the duration of the multi-layer composite is longer than that of the multi-layer pure fabric, indicating that the multi-layer composite has more resistance to impact energy. However, the pure fabric deforms more during the puncture process and can play a certain role in buffering, while the composite material is strong and can play the strength advantage of high-performance materials faster, absorbing energy faster and showing better protection performance.

Conclusion In the study, the isolation of moisture can effectively maintain the rheological properties of the shear thickening solution and the anti-stab performance of its composites, and the design of the laminated structure of different anti-stab composites can maximize the anti-stab performance of the multilayer composites due to the effect of interfacial friction. And take advantage of the performance of different materials to realize the synergy of materials to reduce the weight of composite materials to improve the anti-stabbing performance, and provide a theoretical research basis for the structural design of anti-stabbing layer materials for anti-stabbing clothing.

Key words: multiphase shear thickening fluid, ageing, laminate structure, flexible puncture-proof material, rheological property, aramid fabric