Hybrid Composite Phenolic foams were reinforced with glass and aramid fibers in different proportions. Compression and shear properties of the hybrid phenolic foam were tested and the data was compared to properties of unreinforced phenolic foams and commercial polyurethane (PU) foams. The hybrid foams exhibited greater stiffness and cracking resistance as compared to unreinforced foams. Also the hybrid foams exhibited higher strength and modulus as compared to foams reinforced with only glass and flame resistant meta-aramid fibers (Dupont Nomex). Overall, the mechanical performance of hybrid composite phenolic foam was comparable to commercial PU foams of equivalent density. The experimentally observed mechanical properties (compression) of hybrid foams with different fiber loadings have been compared with existing theories of reinforcement. Composite models such as Halpin Tsai and Hirsch model have been evaluated to fit the experimental data. The results obtained here, coupled with earlier works demonstrate the potential of hybrid composite phenolic foam as a strong, low cost and fire retardant material for sandwich panels.
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