Composite Plate Configurations Research Articles

Behaviour of explosively welded impedance-graded multi-metal composite plates under near-field blast loads

This paper presents a comprehensive analysis of the blast response of functionally graded composite metallic plates, fabricated using explosive welding. Explosive welding is a solid-state welding technique, which has previously shown capabilities in bonding metals that have different chemical and mechanical properties. Impedance, which is the product of volumetric mass density and wave propagation velocity for a given material, was chosen as the function when designing the graded composite plates. The performance of two composite plate configurations, namely, Steel-Titanium-Aluminium and Steel-Brass-Aluminium were compared with a monolithic steel configuration of equal overall plate dimensions. The plates were subjected to highly intensive blast loads produced by detonation of the 250 g cylindrical Composition-B charges at standoff distances between 20–65 mm and spherical 1 kg Nitromethane charges at standoff distances of 200 mm and 250 mm. Detailed numerical models of near-field loading of the monolithic and composite plates were developed using the non-linear finite element analysis software LS-DYNA and validated using the experimental deformation measurements. Experimental evaluation of the impedance-graded explosively- welded composite plates has been carried out for the first time and herein lies the novelty of the work presented in the paper. It was observed that the impedance graded composite plates, which were lighter in density than the monolithic plates, resisted the highly intensive blast loads through their enhanced ductility.

Analytical and numerical investigation of polyurea layered aluminium plates subjected to high velocity projectile impact

This paper discusses on the penetration of high velocity projectiles through aluminium–polyurea composite layered plate systems. An analytical model has been proposed to predict the residual velocity of aluminium–polyurea composite plates, and validated with both experimental and numerical investigations. Full metal jacket (FMJ) projectiles (5.56mm×45mm), corresponding to NATO standard SS109, were fired at the aluminium–polyurea composite layered plate systems from a distance of 10.0m at a fixed velocity of 945m/s. Four different composite plate configurations were used with thicknesses varying from 16 to 34mm. Each configuration consisted of six specimens. Residual velocities for each individual test were recorded. Numerical simulations of the penetration process have been performed using advanced finite element code LS-DYNA®. The well-established Johnson–Cook and Mooney–Rivlin material models were used to represent the stress–strain behaviour of aluminium and polyurea in the numerical analysis. The analytical and numerical models provided good approximations for the residual velocities measured during the experimental tests. Polyurea layers contributed positively towards the reduction of residual velocity of the projectile in composite plate systems. In addition, ballistic limit curves for different composite systems have been established based on the validated models. As the results showed that polyurea contributes positively towards the reduction of residual velocity of projectiles, the findings of this study can be effectively used for the similar applications in future armour industry.

A new lock-free, material finite element for flexure of moderately thick rectangular composite plates

Details of development of a new lock-free, rectangular, material finite element are presented in this paper. The element is named material finite element by the authors as its shape functions, derived from moment-shear equilibrium equations, involve material properties and plate thickness besides the usual element coordinates. Based on the first-order theory of Mindlin, the element with 5 degrees of freedom (dof) at each of the four nodes and the 3×3 Gaussian integration scheme is found to perform consistently well for any plate configuration irrespective of its side to thickness ratio. The usual numerical manipulations of selective integration for analysis of thin plates are not necessary if these elements are employed. Numerical results presented, for various composite plate configurations considered, are found to be in good agreement with those available in the literature, confirming the performance of the element.

Finite element analysis of the non-linear vibrations of moderately thick unsymmetrically laminated composite plates

The influence of finite amplitudes on the free flexural vibration response of moderately thick laminated plates is investigated. For this purpose, a simple higher order theory involving only four unknowns and satisfying the stress free conditions at the top and bottom surface of the composite plate is proposed. The proposed theory eliminates the use of shear correction factors which are otherwise required in Mindlin’s plate theory. A rectangular four-node[formula]continuous finite element is developed based on this theory. The non-linear finite element equations are reduced to two non-linear ordinary differential equations governing the response of positive and negative deflection cycles. Direct numerical integration method is then employed to obtain the periods or non-linear frequencies. The finite element developed and the direct numerical integration method employed are validated for the case of isotropic rectangular plates. It is found that unsymmetrically laminated rectangular plates with hinged-hinged edge conditions oscillate with different amplitudes in the positive and negative deflection cycles. Furthermore, such plates would oscillate with a frequency less than the fundamental frequency for finite small amplitudes of oscillation. It is shown that this behaviour is strongly influenced by the boundary conditions. Results are presented for many configurations of composite plates.