## 1 Introduction  
Dry fabrics based on high strength fibres such as Kevlar and Dyneema are conventionally used for soft body armour due to their high energy absorption capacity against ballistic impact [1]. These materials present a very low bending stiffness due to the lack of resin, resulting in lightweight flexible textiles for personal protection [2]. Their membrane response results in a large amount of energy absorption due to in-plane deformation [3]. They can be divided into woven and nonwoven fabrics depending on the disposition of the fibres in the fabric. Needle-punched nonwoven fabrics present a lower stiffness and strength (as well as processing cost) than their woven counterparts, but possess a higher deformability and excellent ballistic performance against small calibres and shrapnel [4]. It is possible to find in the literature multiple applications for protective barriers based on nonwovenfabrics for soft body armour and the transport industry [5; 6; 7; 8; 9; 10]; nevertheless, the biggest improvement in ballistic performance is obtained when nonwoven fabrics are combined with traditional barriers based on dry woven fabrics, as cushion layers, or metal plates with a negligible increment of the total areal weight of the target [4; 11; 12; 13]. It is possible to find detailed studies focused on the quasi-static response [14; 15] and the ballistic performance of the material [16; 17; 18; 19]; nevertheless, there is still a lack of knowledge regarding the effect of high strain rates in its mechanical properties. For instance, a detailed dynamic characterisation is required to understand the differences in the wave propagation (scattering and dissipation) between a continuous medium and the actual network structure [20]. Moreover, further research is needed to determine the dynamic mechanical properties and developed sound, physically-based strain rate dependent constitutive models with superior predictive capability than the current phenomenological approaches that tuned the stiffness and strength of the fabric to fit the ballistic limit of the layer [21]. The dynamic characterisation of structural materials is usually accomplished with a Split-Hopkinson Bar (SHB) device, that procures the stress-strain constitutive relationships for high strain rates [22]; however, measuring the dynamic tensile response of nonwoven fabrics is a challenging task that presents considerable technical difficulties. For instance: (i) the mechanical characterisation of low impedance fabrics results in a low response in the transmission bar, difficult to register by conventional strain gauges; (ii) their inherent low wave speed makes the transit time much longer than in metallic materials and an equilibrated stress state may not be reached during dynamic deformation [23; 24]. The validity and the accuracy of the experimental data thus need to be examined in detail; (iii) the nonwoven fabrics present high ductility and strain to failure, hence, the time duration of the pulse needs to be long enough to ensure large deformations are applied; (iv) the minimum representative sample size to characterise the fibre network is given by the fibre length of several millimeters, which is orders of magnitude higher than the size of constituents of conventional composite materials, in the order of micrometres [25]. This fact makes necessary the use of large gauge lengths that contain at least one Representative Volume Element (RVE) to reproduce the characteristic mechanical response of the fabric [14; 26]. As a result, the maximum strains and strain rates reachable during the SHB experiment become lower. The transit time also increases, hindering the possibility to attain the force equilibrium state in the bars [27]. To overcome these issues, several solutions have been reported in the literature, mostly applied to the dynamic characterisation of engineering foams and tissues.