Oxidation-induced microstructural changes of a polymer-derived Nextel™ 610 ceramic composite and impact on the mechanical performance

Influence of heat treatment and fiber orientation on the damage threshold and the fracture behavior of Nextel fiber-reinforced Mullite-SiOC matrix composites analysed by acoustic emission monitoring

“…The damage threshold in the present study is related to the sudden increase of the hit rate, which is likely to be caused due to an overlay of matrix cracking and hits generated in the weak interface [16]. As aforementioned, a former study [9] proved a matrix densification and the formation of silica bridges after heat treatments. These strengthening effects are likely to be responsible for the increase of the damage threshold.…”

“…For all samples, the heat treatment was conducted according to [9]. The composites were exposed to 1000°C for 50 and 150 h, and to 1200°C for 50 h.…”

“…8 % after exposure to 1200°C for 50 h. In contrast, the N610 45 composites exhibited an increased stiffness, which was about 20 % higher compared to its as-received state. Previous studies [9,11] regarding the influence of heat treatments on the performance of SiOC containing composites, indicates that both, strength and fracture toughness are affected. The relation between fracture toughness and flexural strength is shown in Fig.…”

“…However, small residual amounts of carbon in the SiOC matrices make them susceptible to oxidation at high temperatures. As a consequence, unprotected composites suffer from a partial or complete closure of the often used fugitive interface between fiber and matrix due to the formation of silica bridges [9][10][11]. The increased interfacial adhesion decreases the fracture toughness and strength of the material [9,11].…”

“…As a consequence, unprotected composites suffer from a partial or complete closure of the often used fugitive interface between fiber and matrix due to the formation of silica bridges [9][10][11]. The increased interfacial adhesion decreases the fracture toughness and strength of the material [9,11]. It is important to improve the structural design, and calculation, of not only the toughness, strength and stiffness changes of these materials, but also the fracture behavior [12] which is likely to be affected by oxidation as well.…”