Effect of rubber encapsulation on the comparative mechanical behaviour of ceramic honeycomb and foam

Cordierite-mullite honeycombs with square cells were prepared by an extrusion technique. Mechanical behaviour of the honeycomb was compared with that of commercial ceramic foam with and without rubber encapsulation. While impact testing, honeycombs as well as foam had shown low energy absorption, which was increased substantially upon rubber encapsulation in both cases. It has been found that the honeycomb absorbs significant amounts of energy under compression when loaded in the direction parallel to channel walls in comparison with when it is loaded in the perpendicular direction. Upon rubber encapsulation, honeycomb had shown substantial decrease in the absorbed energy parallel to channels, whereas, there was modest increase in the perpendicular direction. However, in both the orientations the critical stress was decreased upon rubber encapsulation. The foam on other hand absorbed significantly lower energy under compression in comparison with that of the bare honeycombs. Interestingly, upon rubber encapsulation, the foam had shown increased amounts of energy absorption as well as enhancement in the critical stress, contrary to the behaviour observed in the case of honeycombs. Failure mechanisms for the different types of configurations with and without rubber encapsulation are proposed in this paper. (C) 2002 Elsevier Science B.V. All rights reserved.