The properties of shear thickening fluid (STF), based on polypropylene glycol and amorphous silica, modified by the addition of multiwalled carbon nanotubes (MWCNTs), were studied. The STF’s viscosity increases abruptly during impact tests. The addition of a small amount of carbon nanotubes (CNTs) to the STF, leads to an increase of the maximal viscosity from 2128 to 12,213 Pa$$\cdot $$s. To show the differences between various compositions, the microstructures of fluids were observed by scanning electron microscopy. A pronounced influence of the CNTs on the ability of impact force absorption was noticed. The protective structure containing 55 and 0.25 vol% of fumed silica and CNTs, respectively, is able to absorb up to 74% of impact force.

Polyurethanes (PUR), which are known to exhibit energy absorption properties, have been selected for use as structural elements of the shields protecting the rescuers from the shockwaves. In order to increase the ability of these materials to absorb energy the composite structures containing polyester 3D fabrics have been prepared. Polyurethanes of various hardness (40, 85, 95 ShA) were used in the study. The impact tests were carried out with two analytical methods using Dynatup 9250HV column impact hammer and the impact energy absorption testing setup constructed with accordance to the British standard BS 7971-4:2002. The evaluated polyurethanes with different hardness exhibited similar capabilities of energy absorption (more than 82 J). Introduction of polyester 3D fabrics increased the amount of energy that could be absorbed by the examined composite structures (more than 87 J).

The subject of the paper are semi-rigid polyurethane foams. They belong to a group of energy-absorbing materials, which have been used for manufacture of structural components of protecting shields for firefighters. In order to increase the fire resistance of the foams they were modified by addition of expandable graphite and Fyrol PNX. As a result, flame retardant foams have been obtained, with reduced flammability and limited amount of smoke emission, having an ability to absorb impact energy in the amount of 12-19 %. By introducing a rubber waste during the manufacture of foam composition, the price of foams was reduced by about 25 %.

The elastomeric anti-trauma pad (EA-TP) based on shear thickening fluid (STF) has been developed. Dynamic oscillatory shear experiment was conducted at constant strain amplitude of 5%. STF composed of 25% of volume fraction of 7 nm Fumed Silica, dispersed in polypropylene glycol with molar mass 400 gmol−1 shows elastic properties in entire investigated range of the frequency. Ballistic tests of EA-TP with 7.62 mm × 39 mm PS bullets were performed according to the PN-V-87000:2011 standard. The studies revealed about 60% reduction of the average backface signature depth (BSD) for the EA-TP, when compared to the nowadays commonly used soft insert. The ATR-FTIR analysis confirmed slight impact of the elevated temperature and air (oxygen) on the chemical degradation of the EA-TP surface. The UV-VIS spectroscopy has allowed to notice colour deviation of the aged samples towards green and yellow, as well as lack of dye resistance to accelerated aging process. Thermographic analysis has shown no visible changes of the EA-TP surface and sub-surface during accelerated aging process. The aforementioned small changes on the surface of EA-TP did not affect the ballistic properties of composite armour. EA-TP insert maintains ballistic properties after accelerated aging process which was simulating the period of 6 years according to ASTM F1980 – 07:2002 standard.

The issue of energy absorption during impact is present in various aspects of life. The possibility of dissipating unwanted energy gives huge opportunities for a variety applications such as helmets, car bumpers, smart body armours and protective pads. Nevertheless, there are numerous technical problems with achieving a compromise between good energy absorption efficiency and other important properties such as flexibility, weight and thickness. The article describes a study of composite structures based on shear thickening fluids (STF) and auxetic foams. The composites are developed as a potential component of products with high energy absorbing efficiency. The study reports on the rheological behavior of STF and force absorbing properties of the manufactured composites. In the experiment, two types of STF and eleven types of auxetic foams were used. Force absorbing tests for the produced samples were performed by dropping an impactor with the energy of 5 J. It was proved that the addition of STF to the auxetic foams increases the force absorbing efficiency.

Energy absorbing efficiency of samples made of shear thickening fluids (STF) and polyester spacer fabrics (Baltex TM), closed in silicon moulds, was tested. Various STF were synthesized by using polypropylene glycol, ethylene glycol and nanosized fumed silica with different particles size. The STF was also modified by addition of low density microspheres (AkzoNobel TM). Rheological studies showed that the addition of microspheres significantly increased the shear thickening magnitude (STM) and decreased the density of the STF. The energy absorbing tests, performed by dropping an impactor with energy of 5J, allowed for identification of differences in the energy absorbing properties of the specimens.

The main research objective of this study was to investigate the effect of the impregnation of Twaron® fabric with various shear thickening fluids (STFs) on the stab resistance at quasi-static conditions—being the main parameter characterizing the future application of the impregnated textiles in the scope of the new functionality of the elaborated protection of the multi-layer system. It was found that the STF/Twaron® fabric composites required significantly higher loading than the untreated fabric to achieve spike penetration. In the composite fabric tests, the spike did not fully puncture the material.

The concept of using of shear thickening fluid (STF) in the insert of the lightweight bulletproof vest is presented in this paper. The design of the module of the armour containing STF was developed. This module is located in the special cover between layers of ballistic materials. All the mentioned elements create the flexible insert for bulletproof vest. Various variants of modules containing STF and the results of the inserts firing with the 9 mm Parabellum FMJ bullet are presented. On the basis of the ballistic tests results comparison of the behaviour of different variants of modules during the bullet impact was made, their protective capability was evaluated and the modules with the highest efficiency were selected. The designing, optimization and implementation process of a prototype of the cover for the armour modules containing STF, together with the preparation of the technology of production, were also presented.

Rheological fluids belong to the group of smart materials which can also form a component of some textile products. In this study shear thickening fluids (STF) and magnetorheological fluids (MRF) were synthesised. STF is a colloidal suspension of silica nanoparticles in an organic liquid carrier. The viscosity of STFs depends on the shear rate, which means that for a sufficiently high shear rate their properties change from the characteristic of a liquid to that typical for a solid body. This process is rapid and fully reversible. MRF is a noncolloid suspension of micrometric iron particles in a carrier liquid, usually oil. Under the action of an external magnetic field the particles form a chain-like structure and the MRFs change the viscosity, with their properties becoming characteristic of an elastic solid. In this study flexible body armours which are able to protect limbs were elaborated. Such systems can also be used for other flexible shields such as mates, blankets etc., as well as to find civilian applications, for example sport protective clothing.

It was shown that fumed silica particles (FS), dispersed in polypropylene glycol (PPG), form shear thickening fluids (STF). PPGs with different molar mass were tested. The best combination of the properties (high viscosity, obtained at high shear rate) present the fluids composed of 7 nm FS and PPG 425. The highest volume fraction of FS, which was possible to disperse in PPG 425, was 25%. This fluid exhibited the highest viscosity. The highest magnitude of shear thickening effect was obtained, however, for 17.5 vol.% of the solid phase. Dynamic oscillatory shear experiments were conducted at either a constant amplitude or frequency. The constant strain amplitude tests showed, that for the frequency sweep, the systems showed viscous properties, except that of 25 vol.% of FS in PPG 425, which exhibited elastic properties in almost entire range of the frequency investigated. For the constant strain sweep, for low strains, the elastic modulus and loss modulus were hardly dependent on the strain, but for relatively high strain, this dependency was increasing. Also the complex viscosity was also growing for high strain values.

The concept of using of magnetorheological fluid (MRF) as a part of the insert used in the lightweight, bulletproof vest is presented in this paper. For this purpose, a special design of the module of the armour containing MRF was developed. The modules with layers of ballistic materials placed in the cover, create a flexible insert for bulletproof vest. Ballistic performance of different variants of modules containing MRF was determined. On this basis, comparison of the behaviour of particular variants of modules during the projectile impact was made, their protective effectiveness was evaluated and the modules with the highest efficiency were selected. It was also presented the designing, optimization and implementation process of a prototype of the new construction of the cover for the armour modules containing MRF, together with the preparation of the technology of production.

Composite structures built of para-aramid fabric and shear thickening fluid (STF) are developed in the light of their potential application in smart body armour. The study reports on the rheological behaviour of nanosized silica suspensions. Depending on the oligomer chemical structure and molecular weight, we observe different behaviour under shear stress. The STF composed of PPG400 and containing various volume fraction of FS showed good time stability. The compositions containing 6.5 and 11.7 vol. % of silica maintain their rheological properties, although the composition with the highest concentration of solid phase lost about 20% of its maximum viscosity value after 40 days in a closed vial. The addition of colloidal shear thickening fluids to para-aramid woven fabric (Twaron (R) CT709) showed enhanced ballistic penetration resistance of the elaborated system for Parabellum 9mm bullet.

The article presents the results of preliminary work carried out for flexible body armour systems designs which contained three types of magnetorheological fluid (MRFs). The stab resistance of the multilayered material systems with magnetorheological fluids were inves tigated. Tests were carried out on a newly built rig at the Faculty of Materials Science and Engineering, Warsaw University of Technology. Three different configurations of flexible body armour were made. It was found that samples of the multilayered material system containing MRF had lower depth of deformation by about 30% than the reference samples. The combination of MRFs with para-aramid woven fabrics in several usable forms and/or sheets of ultra-high molecular weight polyethylene fibres gives possibilities for obtaining new types of multi-layered systems protecting effectively against various kind of threats.

Two types of non-Newtonian fluids, magneto rheological (MRF) and shear thickening (STF) fluids, respectively were chosen as candidates for energy dissipation study in smart body armour. A series of magneto rheological fluids was synthesized on a basis of synthetic oil and carbonyl iron. The shear modules for the MRF containing 75 wt% of carbonyl iron, obtained in a magnetic field of 230 kA/m were as follows: complex shear modulus G* - 1.2 MPa, storage modulus G-1.2 MPa and loss modulus G 0.35 MPa. The studies revealed also that the silica fumed, dispersed in polypropylene glycol or polyethylene oxide, demonstrates shear thickening properties. The best combination of the properties (high viscosity, obtained at high shear rate) represents the material composed of the silica fumed (SF) and PEO300. Change of the volume fraction of the SF and variation of the molecular weight of the oligomer enables tailoring of the STF properties. Ballistic tests revealed that the structures containing PE bags with MRF (in magnetic field) or STF can enhance the protective performance of body armours providing their flexibility.