A numerical study on the low-velocity impact behavior of the Twaron(R) fabric subjected to oblique impact

In this study, a finite element low-velocity impact model of Twaron(R) plain-woven fabric was created and analyzed using the commercial code ANSYS(R)-AUTODYN, and then was validated by drop-weight impact experiments. As a bullet or a fragment can strike a protective system from any angle in space, it is necessary to investigate fragment impact behavior response to impact threats from all angles of space. Therefore, in-plane obliquity theta, and spatial obliquity phi, were employed in this study and 17 different simulation test impact scenarios with different impact obliquity values were carried out using a standard hemispherical-head impactor. Results showed that the energy absorption of Twaron(R) fabric decreases with increasing theta, whereas under the same theta, the energy absorption increases with increasing phi. This study also evaluated and compared the low-velocity impact performance of Twaron(R) fabric as a function of impactor shape, such as hemispherical, flat, and ogival heads, with different theta. The results showed that under the same density, volume, and diameter conditions and at the normal impact scenario of a flat-head impactor, the fracture mechanism of the yarn is the same with all impact scenarios for a hemispherical-head impactor; the contacted yarns of the fabric fractured almost simultaneously. For the other oblique impact scenarios of the flat-head impactor, as well as impact scenarios of the ogival-head impactor, the yarns of the fabric fractured intermittently. Additionally, for the impact scenario with the ogival-head impactor, the effect of impact obliquity on energy absorption of the fabric was completely opposite to that of the hemispherical-head impact scenario. This is because in the hemispherical-head impact scenario, the fabric yarn tends to be damaged by tension, whereas in the ogival-head impact scenario, the fabric tends to be damaged by out-of-plane shear. These findings provide important guidance for the engineering of soft body armor and composite materials.