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Abstract
The impact resistance and mechanical behaviour of composite panels utilised in personal armour systems are investigated in this work. The panels considered in the present study are composed of various combinations of resin impregnated rigid layers and unimpregnated dry woven fabric flexible plies assembled in different ways. The multi-layered composite panels are subjected to the impact by a hemispherical-nose projectile and have been either clamped along their edges or rested on an elasto-plastic foundation.
A numerical simulation model has been developed using non-linear finite element code LS-DYNA to predict the impact resistance of different types of composite panels subjected to low, medium and high velocity projectile impact. Shell elements have been used to model both dry fabric plies and resin impregnated composite layers. The projectile and the elasto-plastic foundation have been modelled using 3D solid elements. The failure of the composite panels has been simulated using LS-DYNA explicit dynamics algorithm including Chang-Chang progressive damage model and Matzenmiller, Lubliner and Taylor (MLT) model for composites. The automatic surface to surface contact algorithm which allows for the sliding and separation of the dry fabric plies has been employed to model interaction between the dry layers and contact conditions between the impregnated and dry plies.
Low velocity impact testing has been conducted using a drop tower impact testing rig for various levels of energy. A compressed air gas gun is used to perform medium velocity tests for impact velocities up to 190 m/s. Woven glass fabric reinforced composite panels have been subjected to the low velocity impact and ballistic fabric (Spectra) reinforced composite panels have been tested under medium velocity impact loading.
The results obtained from the numerical analysis have been validated by comparing them with the experimental data. High velocity impact simulations are performed for the hybrid flexible/rigid ply systems reinforced with ballistic fabric (Spectra) subjected to impact by deformable projectile.
It has been shown that the panels made of the resin impregnated rigid plies have demonstrated the lowest value of projectile penetration velocity. It was also found that the combination of dry fabric layers with impregnated rigid plies improved the value of this parameter by 43-48%, 28-40% and 16-33% for panels composed of 12, 24 and 36 layers, respectively. The highest velocity for complete penetration has been observed for the panels composed of dry fabric only. The amount of energy absorbed by the target panel is found to be increased with an increase in the number of dry plies embedded in the panel. The results obtained in this study can be used in practical design of lightweight flexible hybrid composite panels for armour applications.