Mechanical behavior of hybrid composite phenolic foam

Hybrid composite phenolic foams are reinforced with chopped glass and aramid fibers in varied proportions. The mechanical properties are measured and compared with those of foams reinforced with only aramid and glass fibers. The compression and shear properties of the hybrid reinforced foams are also compared with those of commercial polyurethane foams. The reinforced hybrid phenolic foams exhibit greater resistance to cracking and are significantly stiffer and stronger than foams with only glass and Nomex (R) fibers. In general, the mechanical properties of reinforced hybrid phenolic foams are comparable to that of commercial polyurethane foam of equivalent density. The experimentally observed compressive properties (compression modulus) of reinforced phenolic foam with different fiber loading have been compared with existing theories of reinforcement. Composite models such as parallel, series, Halpin-Tsai, and the Hirsch model have been evaluated to fit the experimental data. The findings presented here, coupled with earlier results, demonstrate the potential use of hybrid composite foams as a low-cost engineering material that is tough, strong, and fire retardant.