Aramid fibre has become a critical material for individual soft body armour due to its lightweight nature and exceptional impact resistance. To investigate its energy absorption mechanism, quasi-static and dynamic tensile experiments were conducted on Kevlar^® 29 plain-woven fabric using a universal material testing machine and a Split Hopkinson Tensile Bar (SHTB) apparatus. Tensile mechanical responses were obtained under various strain rates. Fracture morphology was characterised using scanning electron microscopy (SEM) and ultra-depth three-dimensional microscopy, followed by an analysis of microstructural damage patterns. Considering the strain rate effect, a viscoelastic constitutive model was developed. The results indicate that the tensile mechanical properties of Kevlar^® 29 plain-woven fabric are strain-rate dependent. Tensile strength, elastic modulus, and toughness increase with strain rate, whereas fracture strain decreases. Under quasi-static loading, the fracture surface exhibits plastic flow, with slight axial splitting and tapered fibre ends, indicating ductile failure. In contrast, dynamic loading leads to pronounced axial splitting with reduced split depth, simultaneous rupture of fibre skin and core layers, and fibrillation phenomena, suggesting brittle fracture characteristics. The modified three-element viscoelastic constitutive model effectively captures the strain-rate effect and accurately describes the tensile behaviour of the plain-woven fabric across different strain rates. These findings provide valuable data support for research on ballistic mechanisms and the performance optimisation of protective materials.

In this study, we examined the aerodynamic loading on a small caliber rifle (spin stabilized) projectile moving in a muzzle flow field using an element method to analyze the loading and the effect of the angle of attack (for small angles from 0 to 3 deg) on the different components. The temporal pressure distribution on the projectile, which forms the basis of the element method, was computed using a computational fluid dynamics (CFD) analysis combined with a classical interior ballistics model. Then, a high-speed optical experiment was conducted to verify the results of the CFD method and ensure the accuracy of the calculations. The results were as follows: (a) similar to a large caliber projectile, the total axial force, which consisted primarily of the axial forces on the base and boattail, was found to have an inverse exponential relationship with time; (b) the overall lift was a combination of the lift of the base, boattail, cylinder, and nose; and (c) the interaction between the pitch moment of the base and that of the boattail was found to be the primary contributing factor to the total pitch moment. Based on these results, we recommend that the characteristics of the base and boattail be considered when specifying the geometric configuration of a projectile.

The dynamic vibration absorber (DVA) has a broad application background in slender structure vibration reduction, such as in machine gun systems, micro actuators, and so on. Rapid modeling and simulation of the DVA-beam system are of great importance for dynamic performance, evaluation, and finally, the structural design. The primary motivation for this paper is to present a reliable and convenient technique for the modeling and computation of the DVA-beam system. A novel DVA-beam element, which consists of a beam segment and a DVA, is presented. In this element, the DVA position can be arbitrarily allocated, whether on the beam node or within the beam domain. In this way, the beam can be modeled with a few elements to save on computing costs and maintain ideal modeling accuracy. An element deactivating method, which endows the DVA-beam element with the ability to simulate a bare beam and a DVA-beam structure simultaneously, is proposed. Some numerical examples were carried out to validate the reliability of the DVA-beam element in addressing different kinds of boundary conditions by comparing the beam tip responses with those simulated by ADAMS software, and good agreements were observed. Finally, two DVA optimization examples were conducted to investigate the effectiveness and applicability of the DVA-beam element in engineering optimization. The performance was impressive.