11 - Ballistic response of needlepunched nonwovens

Abstract

Needlepunched nonwoven fabrics manufactured with high strength fibres present lower stiffness and strength than their woven counterparts, but possess much higher deformability and energy absorption capacity, leading to an excellent ballistic performance against small calibres. Although their potential advantages, very little is known about their deformation and fracture micromechanisms at the microscopic level and how they contribute to macroscopic mechanical properties such as ballistic limit. This lack of knowledge hinders the optimisation of their mechanical performance and also limits their implementation in structural applications. This chapter aims to review the response of needlepunched nonwovens subjected to ballistic impact. The experimental dynamic characterisation is conducted through a combination of split-Hopkinson bar and impact tests. These procure the wave propagation phenomenon, the dominant deformation micromechanisms at high-strain rates, and the residual velocity curves, including the ballistic limit. In addition, a finite element digital twin is implemented in the software Abaqus/Explicit to explore the influence of the microstructure in the ballistic performance of the material. The numerical model is validated against the previous experimental results and it is employed to analyse the potential of the material to improve the performance of targets such as dry woven fabrics and metal sheets. The addition of the nonwoven layer increases substantially the specific energy absorption capacity of the system, with a negligible increment of the total areal weight of the target.