Fabrication and finite element modeling of ellipsoidal macro-shells

Millimeter-sized composite spherical shells have long been used in syntactic foams for deep sea buoyancy applications. Recent advances in the understanding of particle settling behavior have revealed the enhanced packing factor of non-spherical shapes, especially of ellipsoidal geometries. In order to realize the packing advantage of ellipsoidal composite shells in syntactic foams, the potential mechanical property penalty as compared with spherical shells must be understood. The current investigation used linear elastic finite element models of isostatic compression to elucidate the mechanical difference between volumetrically identical spherical and ellipsoidal macro-shells. Experimental fabrication of glass-fiber/epoxy composite ellipsoidal macro-shells was also performed in order to verify the viability of the current industrial production process for non-spherical geometries. The relevant trends of increasing predicted stresses with increased deviation from sphericity are discussed, and their implications for syntactic foam properties and applications are discussed.