The tribological behaviors of epoxy composites filled with organic functionalized ZrB 2 –Al 2 O 3 were environmentally investigated and compared with those with as-received fillers under both dry and oil sliding conditions in this work. The worn surfaces and the transfer films on the counterparts were characterized by scanning electronic microscope (SEM), and the frictional temperature rising was investigated by infrared thermometer. The results demonstrated that the coefficient of friction (CoF), the wear rate, as well as the frictional temperature rise of the epoxy composites were all decreased due to the introduction of ZrB 2 –Al 2 O 3 fillers. And with the increase in filler content, similar variation tendencies of CoF and wear rate of epoxy composites were observed under the different sliding conditions. Besides, the organic functionalization of ZrB 2 –Al 2 O 3 fillers, which made the epoxy composites exhibit lower CoF and wear rate than those with as-received fillers, lowered the frictional temperature as well. In comparison, the epoxy composites filled with 5 vol% modified fillers presented better tribological properties, suggesting a stronger interfacial bonding between modified fillers and epoxy matrix. The dominant wear mechanisms of filled composites under dry and oil sliding conditions could be inferred as the combination of adhesive wear and abrasive wear and the fatigue wear, respectively, on the basis of SEM images of worn surfaces.
The effect of interfacial modification on flexural strength of epoxy composites filled with modified ZrB 2 -Al 2 O 3 composite fillers was investigated in order to explore the stress distribution of modified composites under external load. The mechanical performance of epoxy composites filled with 0 vol%, 1 vol%, 3 vol% and 5 vol% unmodified and modified ZrB 2 -Al 2 O 3 fillers was characterized by three point bending (TPB) tests. The fracture surfaces of epoxy composites were observed by scanning electronic microscope (SEM). The results showed that the epoxy composite reinforced by 1 vol% modified fillers exhibited the optimal mechanical performance. According to the Von Mises stress contours simulated by finite element models (FEM) and the SEM images, it was shown that the modified ZrB 2 -Al 2 O 3 multiphase fillers could homogenize the stress in the epoxy composites due to the transition effect resulted from the interfacial modification layers on the surfaces of multiphase fillers. It contributed to the improvement of mechanical performance of epoxy composites further.