4. Conclusion
The toughening effect of the short carbon fibers in the
ZrB2–ZrSi2 ceramic composites was investigated. The short carbon
fiber-reinforced ZrB2–ZrSi2 ceramic composites were fabricated via
hot pressing, where the ZrB2–ZrSi2 ceramics without carbon fibers
were used as the reference. The mechanical properties were evaluated
by means of flexural test and SENB test, respectively. The
microstructure was characterized by SEM equipped with EDS.
The following conclusion can be drawn from the current work:
(1) Microstructure analysis revealed that the short carbon fibers
are effectively incorporated in the ZrB2–ZrSi2 matrix. The
relative density of the short carbon fiber-reinforced
ZrB2–ZrSi2 ceramic matrix composites is about 97.92%.
(2) The flexural strength of short carbon fiber-reinforced
ZrB2–ZrSi2 composites is 437 MPa; the fracture toughness
and the work of fracture are 6.89 MPa m1/2 and 259 J/m2,
respectively, which increased significantly in comparing
with the composites without fibers.
(3) Microstructure analysis revealed that the improved fracture
toughness could be attributed to the fiber bridging, the
fiber–matrix interface debonding and the fiber pullout,
which consumed more fracture energy during the fracture
process.
(4) The introduction of carbon fibers can not only improve the
fracture properties of ZrB2–ZrSi2 based ceramic composites,
but also optimize the composition of matrix.