Abstract
This work focuses on the combination of two complementary non-destructive techniques to analyse the final deformation and internal damage induced in aramid composite plates subjected to ballistic impact. The first analysis device, a 3D scanner, allows digitalising the surface of the tested specimen. Comparing with the initial geometry, the permanent residual deformation (PBFD) can be obtained according to the impact characteristics. This is a significant parameter in armours and shielding design. The second inspection technique is based on computed tomography (CT). It allows analysing the internal state of the impacted sample, being able to detect possible delamination and fibre failure through the specimen thickness. The proposed methodology has been validated with two projectile geometries at different impact velocities, being the reaction force history on the specimen determined with piezoelectric sensors. Different loading states and induced damages were observed according to the projectile type and impact velocity. In order to validate the use of the 3D scanner, a correlation between impact velocity and damage induced in terms of permanent back face deformation has been realised for both projectiles studied. In addition, a comparison of the results obtained through this measurement method and those obtained in similar works, has been performed in the same range of impact energy. The results showed that CT is needed to analyse the internal damage of the aramid sample; however, this is a highly expensive and time-consuming method. The use of 3D scanner and piezoelectric sensors is perfectly complementary with CT and could be relevant to develop numerical models or design armours.
Highlights
The current combat helmets are made of polymeric material reinforced with high ballistic resistance fibres, as aramid and high molecular density polyethene fibres
Five non-perforation tests in the range of impact velocity 90 m/s < V < 174 m/s have been carried out for both projectiles in order to observe the influence of the nose type shape on induced damage out for both projectiles in order to observe the influence of the nose type shape on induced damage on plates
The particular use of computed tomography (CT)-scanning for internal plate inspection contrast with other techniques usually carried out, as cross-section cutting, a destructive technique that induces with other techniques usually carried out, as cross-section cutting, a destructive technique that additional damage, or non-destructive ultrasonic inspection, not easy to use due to the high signal induces additional damage, or non-destructive ultrasonic inspection, not easy to use due to the high attenuation in aramid panels in comparison with other materials, as CFRPs or GFRPs
Summary
The current combat helmets are made of polymeric material reinforced with high ballistic resistance fibres, as aramid and high molecular density polyethene fibres. The main feature of the helmet is to minimise the brain injury that may affect the wearer due to blast or ballistic impact. Concerning the ballistic threats classification, combat helmets could be divided into perforating and non-perforating threats. Perforating threats are presented in war scenarios such as metalcore ammunition and long-range bullets [1]. These projectiles require tough materials to stop and break the bullet, as in the case of ceramic in bulletproof vests [2,3]. Non-perforating projectiles are generally made of lead core
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