The study focuses on testing a simplified way of estimating the resultant force due to ballistic impacts resulting in a full fragmentation of the impactor with no penetration of the target. The method is intended to be useful for the parsimonious structural assessment of military aircrafts with integrated ballistic protection systems by means of large scale explicit finite element simulations. The research investigates the effectiveness of the method in allowing the prediction of the fields of plastic deformation collected by hard steel plates impacted by a wide range of semi-jacketed, monolithic, and full metal jacket .308 Winchester rifle bullets. The outcomes show the effectiveness of the method being strictly related to the full compliance of the considered cases with the bullet-splash hypotheses. The study therefore suggests the application of the load history approach only after careful experimental investigations on the specific impactor–target interactions.

Auxetic materials have recently attracted interest in the field of crashworthiness thanks to their peculiar negative Poisson ratio, leading to densification under compression and potentially being the basis of superior behavior upon impact with respect to conventional cellular cores or standard solutions. However, the empirical demonstration of the applicability of auxeticity under impact is limited for most known geometries. As such, the present work strives to advance the investigation of the impact behavior of auxetic meta-materials: first by selecting and testing representative specimens, then by proceeding with an experimental and numerical study of repeated impact behavior and penetration resistance, and finally by proposing a new design of a metallic auxetic absorber optimized for additive manufacturing and targeted at high-performance crash applications.

The present work aimed to develop a semi-empirical criterion able to describe impact events on GFRP and CFRP (glass and carbon fiber reinforced polymers) composite thin laminates: these events are able to generate large damages involving multiple mechanisms such as matrix cracking, fiber failure and, above all, delamination. Main purpose of this research was to obtain an accurate numerical description of the impact region in terms of damage extension and depth without the modelization of the adhesive layers. Starting from an experimental campaign of drop-weight impact tests on representative specimens and the implementation of related numerical Ansys LS-DYNA models exploiting equivalent shell approach, a damage criterion was developed and calibrated and a numerical tool was written and implemented within the LsPrePost, evaluating its reliability by means of correlation with the drop tests.