纤维类型和涂层对纤维增强MoSi2复合材料弯曲性能的影响

以短切碳纤维(Cf)和碳化硅纤维(SiCf)为增强相,并用化学气相渗透法对部分纤维进行炭涂层处理,采用热压法制备了4种纤维增强MoSi2基复合材料(SiCf-MoSi2、SiCf/C-MoSi2、Cf-MoSi2和Cf/C-MoSi2),研究了纤维类型及表面炭涂层对MoSi2基复合材料弯曲性能的影响.结果表明纤维的加入明显提高了MoSi2的抗弯强度,加入5%SiCf和5%Cf的复合材料的强度比纯MoSi2分别提高了9.0%和22.8%,Cf增强作用明显优于SiCf;纤维类型相同时,具有炭涂层的纤维增强效果更显著,5%Cf/C-MoSi2复合材料的强度最高,达到了364.7MPa,比纯MoSi2的强度提高了30%;扫描电镜分析表明,无炭涂层的SiCf与MoSi2基体间存在着明显的裂缝,炭涂层改变了纤维与基体的界面结合;有涂层纤维的断裂机制为首先脱粘然后拔出.

Influence of fiber type and coat on flexural strengths of short fiber reinforced MoSi2 matrix composites

Carbon fiber(C_f)/silicon carbide fiber(SiC_f),with or without carbon-coating,reinforced MoSi_2 matrix composites were fabricated by hot-pressed-sintering to examine the effects of fiber type and coating on the properties of MoSi_2 matrix composites,and to analyse the strengthening mechanism.Results are presented that the flexural strengths of fiber-reinforced composites is enhanced notably;Compared with mono-MoSi_2 base material,the flexural strengths of 5%(volume fraction)SiC_f-MoSi_2 and 5%(volume fraction)C_f-MoSi_2 composites are improved 9.0% and 22.8% respectively;the strengthening effects of C_f is better than that of SiC_f;The per-coating fiber has significant effect on the flexural strengths of composites,the flexural strength of 5%(volume fraction)C_f /C-MoSi_2 composite is the highest,reached 364.7MPa,improved 30%,compared to that of composites without fiber;There is obvious interfacial crack between SiC_f without coating and MoSi_2 matrix,and the interfacial bonding of fiber and matrix is improved by carbon-coating;the fracture mechanism of fiber with coating is de-bonding at first and then pull-out.