Aramid has been proved to have excellent ability to protect against ballistic threats however, it has poor puncture resistance. In this research, flexible fabric materials with outstanding stab resistance were prepared with thermoset–aramid composites coated with SiC particles. The stab resistance and mechanical properties of the flexible fabric composites were evaluated. Results showed that the stab resistance of the thermoset–aramid fabrics was effectively improved by the introduction of SiC particles; however, the tear force was slightly decreased. Composites coated with 20 wt.% SiC particles exhibited the best stab resistance against knife cut. Scanning electron microscopy observation showed that the irregular SiC particles were embedded into the gaps among aramid fibers. The increased stab resistance was ascribed to the fact that the introduced SiC particles with hard and refractory nature could highly enhance the fiber-to-fiber friction and blunt the sharp metal blade by abrasion.
Stab-resistant body armor can effectively prevent sharp instruments from attacking the protected parts and reduce the threat to human bodies. Shear thickening fluid (STF) is a kind of smart material with variable viscosity and its viscosity can change significantly with external stimuli. The soft and adaptive characteristics of STF provide a new idea for improving the performance of stab-proof materials. In this work, three kinds of soft anti-stabbing materials were designed and prepared with aramid, poly–p–phenylene benzodioxazole (PBO), and carbon fiber fabrics impregnated with STF. Quasi-static puncture tests and dynamic impact tests were conducted to compare the performance of different anti-stabbing structures. The results showed that the peak piercing force of the STF-treated fabrics in the puncture testing was greatly increased than that of neat samples. Against the D2 knife, the maximum impact load of STF/PBO fiber fabric was increased from 55.8 N to 72.9 N, increasing by 30.6%. Against the D3 spike, the maximum impact load of STF/aramid fabric was increased from 128.9 N to 254.7 N, increasing by 197.6%. The mechanical properties of fibers were important factors for the resistance to knives, and the fabric structure was the key point to bear the spike. Optical photographs of fabric fractures and scanning electron microscope analysis indicated that the STF effectively limited the slip of the fiber bundle when the tool penetrated the fabric, which played a positive role in maintaining the tightness and integrity of the fabric structure.
Liquid armor prepared with shear thickening fluid (STF) and high-performance fiber fabric is a novel body protection material which possesses both anti-impact performance and improved wearing comfort. In this work, the rheological behaviors of STFs with different features and mechanical properties of STF impregnated fabrics at different temperatures were characterized. Three kinds of STFs were prepared by mixing silica particles and polyethylene glycol with different particle concentrations and/or particle-fluid interaction. Their rheological behaviors show remarkable differences in viscosity, loss modulus and storage modulus. High solid concentrations and strong particle-fluid interaction are considered to be important factors to obtain high viscosity and high modulus. The rheological properties of STFs are also very sensitive to temperature, as we have found that the viscosity and the modulus values at −40 °C are three orders of magnitude higher than those at 55 °C. However, the mechanical properties of the aramid fabrics impregnated with these STFs do not change significantly with the STF types and temperature. Yarn pull-out and dynamic impact tests results show that fabrics impregnated with STFs possess excellent energy absorption effects, but the friction resistance and energy absorption capacity of the fabrics are not positively related to the STF viscosity and modulus. Our findings will provide guidance to the design of STF composites in the field of low-speed impact.
The rheological properties of shear thickening gel(STG) and its application as protective composite were studied in the paper. Upon applying a shear stress with excitation frequency from 1 Hz to 100 Hz, the storage modulus (G’) of the STG increases from 101 Pa to 105 Pa, demonstrating an excellent shear thickening effect. The reduction of temperature increases the G’min of STG, but when the temperature reaches at 50°C, the G’ curve shows a moderate slope and a gradual transition to the constant plateau value. By introducing STG into polyurethane foam and kevlar fiber with dip and dry method, successfully fabricate a nove safeguarding polymer composite. The protective performance of composite protective materials was studied by static compression experiment and drop hammer impact experiment. The addition of STG increases the impact resistance and puncture resistance of PU and kevlar by at least two times. The materials shows excellent shear stiffening effect, creep resisting and impact resistant propertie.
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