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This work investigates the effect of hybridization and stacking sequence on the ballistic impact response of S2-glass/aramid/epoxy laminates. Different laminates were manufactured by vacuum infusion, one with only aramid fabrics (12 layers, K12), two with only S2-glass fabrics (12 or 18 layers, Gl12 and Gl18) and five interply hybrids (Gl3K9, [GlK]6, K6Gl6, Gl6K6, Gl9K3). Ballistic tests were performed according to EN1522- FB3, with the .357 Magnum FMJ projectile. The ballistic curves were determined to obtain the ballistic limit velocity (VBL), and in-plane damage area and through-the-thickness damage were analyzed. For the impact at 430 m/s, all laminates were perforated, and the Gl18 exhibited greater specific absorbed energy (26.6 J.m2/kg), with lower thickness and in-plane damage than the K12 (22.6 J.m2/kg) with a similar areal density (≈0.77 g/cm2). No significant differences in ballistic limits (pairing effect) were observed for the [GlK]6, Gl6K6 and K6Gl6 hybrids, and the Gl3K9 hybrid exhibited a positive hybrid effect. The areal density of laminates has shown a great influence on the final ballistic response. The results have shown that hybridization of aramid composites with S2-glass may enhance the impact absorption capability of hard composite armors, however, the ballistic limit velocity, which is a crucial parameter to assess ballistic shield performance, reduced.

The silicon carbide (SiC)/metal composite armors with the composite cover on the front of the SiC plate were impacted by 12.7mm armor piercing incendiary (API) projectiles at velocities from 412.6m/s to 802.2m/s. The resulting projectile core and ceramic fragments were collected and then screened through a range of standard sieving screens. The mass distributions of fragments produced by projectile and ceramic impacting each other were obtained. The failure mechanism of the rigid-brittle core of 12.7mm API projectile after impacting SiC/metal composite armor was studied by examination of the failed core. The results show that the cumulative mass of core and ceramic fragments follow the Schuhmann distribution law. With the increase of impact velocity, the mass proportion of small core fragments increases, while for ceramic fragments, the mass proportion of fragments in different fractions does not change. The failure mechanism of the large equivalent diameter fragment ( >8mm) is tensile brittle fracture mainly. In contrast, the local plastic shear fracture exists on the fragments with an equivalent diameter of less than 2mm.

The capability of poly(ethylene-co-methacrylic acid) (E/MAA) to self-heal is well known, however, its mechanical properties are weak. In this study, composites with single and double layers of unidirectional (UD) carbon fibers were prepared by compression molding. Even a low mass fraction of fibers substantially improved the polymer. The flexural and tensile properties were tested at 0°, 45° and 90° fibers direction and compared to those of the matrix. The mechanical properties in the 0° direction proved superior. Flexural properties depended on the reinforcement distance from the stress neutral plane. The tensile modulus in the 0° direction was 13 times greater despite only a 2.5% mass fraction of fibers. However, both tensile modulus and strength were observed to degrade in the 90° direction. Dynamic mechanical analysis showed the dependence of both structure and properties on the thermal history of E/MAA. Tensile tests after ballistic impact showed that the modulus of the self-healed E/MAA was not affected, yet the strength, yield point, and particularly the elongation at break were reduced. A composite with higher fiber content could be prepared by mixing milled E/MAA particles in fibers prior to compression.

The anti-ballistic properties of a new advanced composite armor system have been investigated with the aim to minimize the armor system total weight per unit area. The innovative protection, made of a silicon carbide ceramic outer layer and an inner composite back-packing layer formed by ultra-high molecular weight polyethylene (UHMWPE) fibers, namely $$\hbox {Dyneema}^\circledR $$ Hard Ballistic 26, was realized and then tested performing dedicated ballistic impact tests. In order to investigate its permanent deformation, ceramic cracking, dimension of the rupture, and extension of the impact damage, nondestructive and destructive tests were conducted on the tested panels. The experimental results were used to develop and validate a transient nonlinear dynamic simulation model of the high-velocity impact of a 7.62 AP bullet on the tested armor system. After an accurate setting of the parameters involved in the description of the material constitutive models and of the involved physical phenomena, a complex numerical model was developed in the $$\hbox {ANSYS-Autodyn}^\circledR $$ environment using both mesh and meshless approaches at the same time. The comparison reveals a good agreement between experimental and computational results in terms of ballistic properties, deformations, fragmentation, and fracture of the ballistic armor system. Hence, a new numerical model for the design and the optimization of the ballistic efficiency of composite armor systems was developed and can be now used in current practice.

With the overall goal to clarify the physics of com pressible (supersonic) combustion, a 3D LES of the HyShot supersonic combustor has been performed and is reported in this paper. HyShot is an (originally) Australian p rogram to assess feasibility of supersonic combustion by means of a ballistic test flight. The HyShot combustion chamber is shaped as a box 75x9.8 mm in cross section and 300 mm long. Hydrogen is injected at 90 degrees with respect to the superson ic airstream 40 mm downstream from the combustor inlet by means of four 2 mm diameter choked orifices. Air enters the channel at a Mach number that, in the actual te st, depended on the flight trajectory; in this simulation, the trajectory poi nt is that at height = 28 km, where the Mach number was 2.79, P=82.11 kPa and T = 1229 K. A structured grid of about 14x10 6 nodes discretizes the actual combustor shape, wher e hydrogen-air combustion is treated by means of a detailed chemical kinetics model including 9 species and 37 reactions. Numerical results indicate that hydrogen penetrates in the air stream generating 3D bow shock structures upstream of the injection orifices as seen in experiments. In these regions recirculation zones u pstream and downstream of the fuel injection orifices are observed as expected; the OH predicted by LES indicates that a flame starts already in the upstream recircu lation zone. Interactions among the essentially 1D airstream entering the combustor, th e heat released and the 3D jets produce large vorticity rates and therefore enhance and accelerate turbulent mixing. Combustion is predicted very fast and efficient: on ly 0.5% of hydrogen is found unburned at the combustor exit.