Impact Response Of Honeycomb Sandwich Structures

Abstract

newline ABSTRACT newlineDesign and development of lightweight structures has drawn major attention of the newlineresearchers and engineers from last few decades due to its low material cost and newlinehigher stiffness to weight ratio. In this perspective various structures such as newlinehoneycomb, foam structures, multi cell tubular structure, frusta have been developed newlineand their energy absorption characteristics were explored against static, fatigue and newlineimpact loading either through experimentation or numerical analysis. newlineIn this context sandwich structures has widely used in automobile, newlinelocomotives, naval and aerospace industries due to its superior energy absorption newlinecharacteristics. In the present study experiments and finite element simulations have newlinebeen carried out for studying the response of hemispherical, cylindrical and flat newlinesandwich structure with metallic honeycomb as core material. The perforation newlinephenomenon, failure mechanism, transverse deformation, residual velocities, ballistic newlinelimit and energy dissipation in different deformation modes of the sandwich structures newlinewere studied against conical, ogive and hemispherical nosed projectile impact. For newlineface sheet in the sandwich structure aluminum alloy 1100-H12 was used whereas newlinealuminum alloy Al - 3003 H18 was considered for hexagonal honeycomb core newlinematerial. For hemispherical sandwich, two hemispherical face sheet of thickness 1 newlinemm, radius 100 mm and 80 mm for outer and inner shells respectively was used. For newlinecylindrical sandwich, cylindrical face sheet thickness 1 mm, length 200 mm and outer newlineshell radius 100 mm and inner shell radius 80 mm was used. For flat sandwich newlinestructure circular flat face sheet of thickness 1 mm and effective span radius 100 mm newlinewas used. Honeycomb core of cell wall thickness 0.05 mm, cell size 3.2 mm and core newlineheight 20 mm was used for all three sandwich structure. Conical, ogive and newlinehemispherical projectiles of diameter 19 mm, length 50.8 mm and mass 52.5 gram newlinewere hit on the centre of the sandwich structures. newlineA pneumatic gun was employed to launch the projectiles over the targets in newlinethe sub-ordinance velocity range. The impact and residual velocity of the projectiles newlinewas measured with the help of an Infrared sensor. The projectile was fabricated of newlineEN24 steel and hardened before use in the experiments. For numerical simulations, newline3D finite element model was developed in commercially used Abaqus/Explicit solver. newlineJohnson cook simplified material with a fracture model was used for face sheets for newlineiii newlinehemispherical, cylindrical and flat sandwich structure, whereas ductile damage newlinematerial model was used for honeycomb core and adhesive. The kinematic contact newlinealgorithm with, the surface to surface contact define between the shell structure and newlinethe projectile, and sandwich subparts and projectile. Tied contact was used to model newlinedebonding between the face sheet and the core. The explicit solution scheme of the newlinefinite element code was employed to simulate the perforation phenomenon. newlineFor sandwich structure, conical and ogive nose shape projectile was found to be newlinean efficient penetrator and required less energy for perforation, whereas hemispherical newlinenosed projectile required higher energy for perforation. In case of conical and ogive newlinenosed projectile, both face sheets were failed in ductile tearing with petals formation newlinewith core in buckling and crushing. For hemispherical nosed projectile sandwich face newlinesheets were failed in ductile shearing with plug formation and the core in normal newlinecrushing. Also, the face sheet thickness played an important role in energy absorption newlineand ballistic limit. From energy absorption point of view, the rear face sheet newlinecontributed the highest energy absorption followed by the front face sheet and core