No abstract

Aluminized high explosives are known to give better underwater performance. All explosive formulations for underwater targets are filled into warheads and shells by casting method. TNT, a high explosive is used as casting medium due to its lower melting point. Plastic bonded explosives are fast replacing TNT-based high explosive formulations for the reasons that they are more insensitive and low vulnerable explosives with better shelf life. Few aluminized plastic bonded explosive formulations based on RDX, aluminum, and HTPB have been processed, varying the aluminum content from 0 to 35% and evaluated underwater. The present paper discusses the experimental methodology adopted to evaluate the above formulations for their ballistic parameters, viz., peak over pressure and impulse. Explosion bulge tests have been conducted with each explosive formulation and extent of bulge in test plates is presented and compared with a standard underwater explosive, viz., HBX-3.

Vibration damping is proving important for improved vibration and noise control, dynamic stability, fatigue, and impact resistance in advanced engineering systems. In the present work, the effect of natural rubber particle inclusions on the mechanical and damping properties of epoxy-filled glass fibre composites is investigated. Test specimens are fabricated with inclusion of natural rubber particles of different sizes and tested for tensile strength, tensile modulus, flexural strength, and flexural modulus. These mechanical properties are influenced by the size of the rubber particle inclusions. Vibration tests are carried out and damping ratio is calculated. It is observed that damping ratio varies with inclusion of natural rubber particles and that 0.25 mm particle inclusions improve damping better than other selected particle sizes without greatly affecting the stiffness in the case of cantilever beams and fixed free plates.

Conventional materials are being replaced in the field of engineering by composite materials, due to their tailorable properties and high specific properties. These materials are extensively used in structural applications. Damping is one of the important properties of the materials used in structures, and needs to be enhanced in order to reduce structural vibrations. In the present work, the improvement of the material damping of glass fabric epoxy composites with particle rubber inclusions is studied. The effect of particle size on the damping and stiffness parameters at different frequencies and temperatures is studied experimentally. Considerable enhancement in damping without significant reduction in stiffness is observed at lower particle sizes. The damping property in both bending and shear modes is more with 0.254 mm rubber particle inclusions among the selected sizes. A lower reduction in stiffness is observed with the inclusion of lower particle sizes (0.254 mm and 0.09 mm) when compared with higher particle sizes. An ANN-based prediction model is developed to predict these properties for a given frequency/temperature and particle size. The predicted values are very close to the experimental values with an maximum error of 5%.

Experimental and numerical investigations on cylindrical shell panels subjected to underwater explosion loading are presented. Experiments were conducted on panels of size 0.8 × 0.6 × 0.00314 m and shell rise-to-span ratiosh/l= 0.0, 0.05, 0.1 , using a box model set-up under air backed conditions in a shock tank. Small charges of PEK I explosive were employed. The plastic deformation of the panels was measured for three loading conditions. Finite element analysis was carried out using the CSA/GENSA [DYNA3D] software to predict the plastic deformation for various loading conditions. The analysis included material and geometric non-linearities, with strain rate effects incorporated based on the Cowper-Symonds relation. The numerical results for plastic deformation are compared with those from experiments.