Energy balance modelling of high velocity impact effect on composite plate structures

Purpose: In many military applications, composite materials have been used because of their high velocity impact resistance that helps absorption and dispersion energy. It is therefore used in armour and vehicles, aircraft and spacecraft that are subjected to impact of various shapes and velocities. Design/methodology/approach: In the theoretical part, the absorption energy equation for the sample was established by constructing an energy balance equation consisting of five types of energies, it is the compressive energy in the first region (the impact region), the tensile energy in the first region, the tensile energy in the second region, the energy of the shear plugging and the friction energy. Findings: It was found in the experiments that the tensile stress value increased by increasing the volume fraction of fibres to the polyester, and the value of compressive stress decreased. Also manufactured different types of impact samples with dimensions (20*20 cm2 ) and deferent thickness. The results were an increase in the amount of energy absorbed by increasing the ratio of the fibre to the polyester. It is found that the greatest effect in the equation of energy balance is the shear plugging energy, in which the value of the energy absorbed reached 38% of the total energy. And in the second degree friction energy, in which the value of the energy absorbed reached 27% of the total energy. while the other energies are relatively small but with important values, except for the tensile energy in the second region, the Kevlar-Polyester (40-60)%, so that the increase was more than four times the previous case. Research limitations/implications: Three types of reinforcing fibres were used: Kevlar, Carbon and Glass fibres with a matrix material as polyester. Six samples are made for tensile and compression testing, Kevlar-Polyester (30-70)%, Carbon-Polyester (30-70)%, Glass-Polyester (30-70)%, Kevlar-Polyester (40-60)%, Carbon-Polyester (40-60)% and Glass-Polyester (40-60)%. Practical implications: On the experimental part, experimental work tests were carried out to determine the mechanical properties of the samples such as tensile and compression tests as well as conducting the natural frequency test conducting the impact test by bullet to identify the effects and penetration incidence and compare this with the theoretical results. Originality/value: In this research high velocity impact is used with a bullet it diameter 9 mm, mass of 8 g, and a semi-circular projectile head with a specific velocity ranging from 210-365 m/s. The effect of the impact is studied theoretically and experimentally. The elastic deformation is increased for increasing the ratio of the fiber to the polyester and the depth of penetration is decreasing. The hybrid sample is affected in absorption energy and decreasing the penetration. Finally calculated for penetration behaviour theoretically and experimentally for different composite materials and comparison for the results calculated.

Perforation Modes of Double-Layered Plates With Air Gap Struck by a Blunt Rigid Projectile

The failure modes of the perforation of double-layered or multi-layered plates may be quite different. Further experimental analyses are conducted on the perforations of single and double-layered Weldox E steel plates with air gap to discuss the different perforation modes. It indicates that, in case of higher initial striking velocity, the failure mode of the first layer plate is adiabatic shear plugging, whilst the failure mode of the second layer plate is adiabatic shear plugging or shear plugging as the striking velocity of the projectile slows down. It concludes that the final failure mode of the double-layered plates is the hybrid of shear plugging and adiabatic shear plugging.

On the Influence of Fracture Criterion on Perforation of High-Strength Steel Plates Subjected to Armour Piercing Projectile

This paper presents a numerical investigation of fracture criterion influence on perforation of high-strength 30PM steel plates subjected to 7.62x51 mm Armour Piercing (AP) projectile. An evaluation of four ductile fracture models is performed to identify the most suitable fracture criterion. Included in the paper is the Modified Johnson-Cook (MJC) constitutive model coupled separately with one of these fracture criteria: the MJC fracture model, the Cockcroft-Latham (CL), the maximum shear stress and the constant failure strain models. A 3D explicit Lagrangian algorithm that includes both elements and particles, is used in this study to automatically convert distorted elements into meshless particles during the course of the computation. Numerical simulations are examined by comparing with the experimental results. The MJC fracture model formulated in the space of the stress triaxiality and the equivalent plastic strain to fracture were found capable of predicting the realistic fracture patterns and at the same time the correct projectile residual velocities. However, this study has shown that CL one parameter fracture criterion where only one simple material test is required for calibration is found to give good results as the MJC failure criterion. The maximum shear stress fracture criterion fails to capture the shear plugging failure and material fracture properties cannot be fully characterized with the constant fracture strain

Numerical Simulations of the Perforation in Metal Plates with Different Conical-Nosed Projectiles

Numerical simulations with ABAQUS/Explicit into which Johnson-Cook constitutive relation is incorporated, are performed to study the perforation of Weldox 460E steel plates struck normally by conical-nosed projectiles with different cone angles. Different failure modes and perforation process are obtained. Numerical results are found to be in good agreement with available test data. It is revealed that with increasing cone angle, the failure modes of metal plates become to shear plugging from ductile hole enlargement, and the ballistic limits decrease with that. The conclusions are helpful for the design of protective structures.

A semianalytical and numerical study of penetration and perforation of an ogive-nose projectile into concrete targets under normal impact

In this article, a semianalytical model is proposed to predict the penetration depth of an ogive-nose projectile into a concrete target. In addition, the theory of shear plugging is used to calculate the residual velocity of the projectile following complete perforation of the target. In this analysis, which is based on the Forrestal model, conservation of energy was employed to determine the axial forces on the projectile and target during both the penetration and perforation stages and the governing equations were derived in each case. The tests were then simulated numerically with the finite element code LS-DYNA and good agreement was obtained with both experimental data and the predictions of the analytical model.