Determination of changes in the mechanical properties of polymer composites with the addition of agglomerates of WC nanopowder

Recently, there has been a growing interest in the development of new composite materials with improved characteristics. The article presents the results of tests of composite specimens based on aramid fabrics modified with WC nanopowder agglomerates obtained from carbide manufacturing waste. The following mechanical characteristics were investigated: transverse bending resistance, fracture resistance and energy absorption during contact with a physical body at high speed. According to the results, the transverse bending resistance increased by 35% at a WC concentration of 5%. When 3% WC powder was added to the matrix composition, the total crack length after impact was almost halved. The largest increase in energy absorption of the samples was about 30% at 1% additive concentration. The significant increase in the investigated parameters can be explained by the complex morphology of the embedded particles. In further investigations it is planned to study in detail the mechanism of distribution of nanodispersed WC powder additive in the volume of the modified material.

Impact Response of Aramid Fabric-Reinforced Polybenzoxazine/Urethane Composites Containing Multiwalled Carbon Nanotubes Used as Support Panel in Hard Armor

The aim of this research project is to analyze support panels that are based on aramid fabrics which are reinforced with polybenzoxazine/urethane (poly(BA-a/PU)) composites and contain multiwalled carbon nanotubes (MWCNTs). Through the measurement of mechanical properties and a series of ballistic-impact tests that used 7.62 × 51 mm2 projectiles (National Institute of Justice (NIJ), level III), the incorporated MWCNTs were found to enhance the energy-absorption (EAbs) property of the composites, improve ballistic performance, and reduce damage. The perforation process and the ballistic limit (V50) of the composite were also studied via numerical simulation, and the calculated damage patterns were correlated with the experimental results. The result indicated hard armor based on polybenzoxazine nanocomposites could completely protect the perforation of a 7.62 × 51 mm2 projectile at impact velocity range of 847 ± 9.1 m/s. The results revealed the potential for using the poly(BA-a/PU) nanocomposites as energy-absorption panels for hard armor.

Anti-Ballistic Properties of Aramid Fabrics and Composites: A Review

In studies of ballistic impact, the materials used in body armor must have high hardness, light weight, fatigue resistance, corrosion resistance, and other high performance characteristics. Aramid fibers are widely used in anti-ballistic materials. To facilitate the further development of aramid materials, this study reviews aramid research in recent years and analyzes the main factors affecting, and new methods for optimizing, anti-ballistic performance, with the emphasis on bulletproof fabrics. This review provides suggestions for future research and use of aramid materials for anti-ballistic performance.

Influence of incident energy on the properties of arc rated para-aramid fabric

To study the protection mechanism of para-aramid fabrics under an electric arc, the structural composition, surface morphology, and thermal properties of an untreated para-aramid fabric and that treated with different incident energy arcs were compared. The intensity of the N-H peak of the para-aramid cellulose amide decreased with increasing exposed arc energy. Moreover, intensities of the C=O peak of the amide bond type I carbonyl and the C-H deformation vibration absorption peak originating from the benzene ring gradually weakened. In contrast, the carbon content of the fabric increased. In the arc deflagration process, the fiber broke and then carbonized and embrittled. With an arc energy of 30.9 cal/cm2, the carbonization degree of the front surface of the fabric increased and was highest at the float line. The initial combustion temperature remained unchanged, and the mass residual quantity gradually increased with increasing arc energy exposed to the fabric. The above results suggest that para-aramid fabric can protect the end user in an arc by carbonization, offering effective assistance in the research and development of personal protective equipment for arc flashes.

Theoretical prediction and experimental characterization of radiative properties and thermal conductivities of fibrous aramid fabrics

Nonwoven aramid fabric is widely used as thermal barrier of fireproofing clothing due to its inherent flame retardancy and light weight. In fire or high temperature scenario, radiative heat transfer becomes the predominant heat transfer mode inside firefighters’ clothing. In this work, Fourier transform infrared spectroscopy (FTIR) was adopted to measure the spectral transmittance and spectral extinction coefficients of four aramid fabrics with different porosity in infrared wavelength range between 2.5 and 25 μm. It was found that the radiative properties of fibrous aramid fabric are strongly dependent on its bulk density or porosity. The spectral extinction coefficient decreases with increasing porosity or decreasing bulk density. The infrared optical properties combined with infrared imaging measurements demonstrate that aramid fabric may be used as infrared semi-transparent textile. A predicted model, combined the effects of conduction-radiation heat transfer, has been developed to calculate the effective thermal conductivity of aramid fiber materials. The model implemented the Rosseland diffusion approximation to evaluate radiative thermal conductivity, and the Parallel-Series structural model to evaluate tortuosity-weighted phonic thermal conductivity. The predicted results were also compared with experimental data obtained from TPS method. This work provides useful information for future studies of heat transfer mathematical modeling of firefighters’ clothing.