Experimental Study of Lightness Factors and Loading Abilities of Sandwich Structures

Abstract

Abstract

The objects of interest are glass-fiber-reinforced-plastics (GFRP) and carbon-fiber-reinforced-plastics (CFRP) composite sandwich shells with a foam core.  Such a structure has been common since the beginning of composite applications in aircraft construction. The strength-lightness factors of typical sandwich structures are large in comparison to laminate structures without a foam core.  However, the loading abilities of laminate structures are not fully consumed in both structures.  For example, a typical GFRP sandwich shell in a glider wing spar shear-web is able to consume about 60% of loading abilities of pure GFRP laminate subjected to tension load along the warp direction.  This is caused by buckling phenomenon of the shell under shear loads. The significant influences on the buckling phenomenon have physical properties of the foam core material and the relation between elastic modules of the foam core and laminate shell.  When the same kind of foam core is applied for CFRP sandwich structures, the level of CFRP laminate loading ability to consume is worse than in GFRP sandwich structures.  This feature of sandwich structures could be improved by application of additional reinforcement inside the foam core.  Described are the successful results of experimental investigations aimed to improve loading abilities of CFRP sandwich shells without worsening the strength-lightness factors.