Enhancing specific strength and stiffness of phenolic microsphere syntactic foams through carbon fiber reinforcement

Composite syntactic foams with different densities were fabricated with hollow phenolic microspheres, a phenolic resin binder, and a small addition of chopped carbon fibers. Compressive, shear, and tensile properties were studied for the syntactic foams with and without carbon fibers. Two fiber layer orientations, either parallel (P‐type) or perpendicular (N‐type) to the loading direction, were considered in the mechanical testing. For N‐type foams, mechanical properties were weakly dependent on foam density. For P‐type foams, the mechanical properties of the foams were strongly dependent on the strength of the supporting matrix. The specific strength and specific stiffness of the P‐type foams were significantly enhanced compared with the neat foams. These findings indicate that fiber reinforcement is an effective way to enhance the mechanical performance of syntactic foams, and the enhanced performance should lead to applications as a foam core material for sandwich structures. POLYM. COMPOS., 2010.