Efthimios Giannaros, Athanasios Kotzakolios, Stavros Tsantzalis, George Sotiriadis, Vassilis Kostopoulos

CHALLENGE - The para-aramid fabric materials are widely-known for their application in blast and ballistic protection systems, such as body armor, combat helmet, vehicle armor and security aircraft systems, to resist high-velocity penetration. This research aims for the effective design of textile systems which should be capable of absorbing the maximum possible energy against ballistic impact. The continuing effort to reduce the cost of experimental campaigns have motivated the researchers to further elaboration using computational-based engineering analyses. 

SOLUTION - Three calibration steps for material characterization and one verification step of numerical model were required. In the first step, an optimization algorithm using the modeFRONTIER was designed to determine the best combination of model's parameters in order to fit the experimental tensile load-strain curve with the corresponding numerical curve. The above approach emerged from the fact that the use of typical yarn properties did not provide reasonable results during the initial effort to predict the amount of absorbed energy without the calibration of the material model. The second step was similar to the first one but the fitting of experimental and numerical fabric deformation values was the target. Whereas the third step addressed the yarn failure stress calibration taking into account the experimental pre-impact and after impact velocity of the projectile. In the final step, a comparison procedure between experimental and numerical residual velocity of the projectile was used as a verification criterion of numerical code and material model. This methodology was individually applied for each of the used fabric materials. 










BENEFITS - Results show that yarn-strain energy is the main energy carrying mechanism, the kinetic energy represents an additional significant mechanism whereas the frictional energy ranged from 2% to 8.2% of overall transferred energy. Also, the plain weave fabric with areal density 400 gr/m2 presents the higher absorbed energy for 75 m/sec impact loading in relation to other fabric configurations, whereas the 260 gr/m2 tri-axial braided fabric is the second in ranking.