Characterization of Integrated Functionally Gradient Syntactic Foams

Light weight high strength composites can be obtained by reinforcing resin with fillers such as hollow or solid particles and fibers. Composites were fabricated using microballoons (hollow particles) called syntactic foams. These foams can be used in various low density applications such as buoyancy aid materials for deep sea exploration and aerospace vehicles. These foams are usually utilized as light weight core materials for sandwich structures. The present study explores the procedure to fabricate functionally gradient syntactic foams (FGSFs) and further analyze their mechanical properties. The FGSFs produced are gradient structures consisting of four layers with four different types of microballoons, namely, S22, S32, S38, and K46, each having different wall thickness. The volume fraction of all microballoons is maintained constant at 60% to maintain light weight structures. Several FGSF specimens having similar density are fabricated with different layer arrangements. The different layers are integrated before major solidification takes place. Quasistatic compression testing is then performed on the cured FGSF samples using MTS-810 servohydraulic machine. Compressive strength and energy absorption values for each arrangement are compared. The stress plateau in integrated FGSF composites extends from 10% to 60% strain compared with plain syntactic foams. The integrated FGSF shows increment in yield strength and energy absorption compared with adhesively bonded FGSF. It is found that the compressive strength and energy absorption of integrated FGSF composites can be varied based on arrangement of the layers.