The Evaluation of the Actual Fracture Energy of the Carbon Fiber Reinforced Silicon Nitride Composite by the Kr-BET Adsorption Technique

Abstract

The fracture surface area of the chevron-notched carbon fiber reinforced silicon nitride composite was measured by the Kr-BET adsorption technique. The energy-absorbing mechanism of the composite was discussed on the basis of the actual fracture energy. The average actual fracture energy of the composite is nearly the same as the fracture energies of polycrystalline ceramics. This fact suggests that the large energy-absorbing capacity of the composite depends on how the fracture surface area can increase. Furthermore, application of the loading/unloading technique reveals that the actual fracture energy of the composite increases to a maximum at an initial stage of the failure, and then decreases to a constant value at a final stage. This indicates that the energy-absorbing mechanism changes from the formation of the fracture surface to the pullout of fibers.