先进复合材料高效加工表面质量稳定性

Stability of surface quality in high efficient performance for advanced composites

针对陶瓷基复合材料的难加工问题,开展长度300和500 mm连续表面磨削加工试验,分析典型损伤特征,利用3D表面粗糙度参数S_(a)、S_(z)、S_(sk)、S_(ku)、S_(dr)和S_(bi)综合评价加工表面形貌,系统研究不同加工长度连续表面的质量稳定性。结果表明:磨削加工后的有效长度超过70%,但是会随机出现剥落损伤和过切损伤;剥落损伤源自涂层-复合材料界面的低结合强度,过切损伤源自理想加工表面与纤维编织层间的微小偏角误差;剥落损伤和过切损伤会造成陶瓷基复合材料层孔隙裸露,破坏表面完整性,影响表面气密性,但未观察到加工导致的孔隙缺陷扩展现象;去除上述损伤位置,加工表面光滑平坦,呈现镜面状态,能够提供更好的承载能力和更低的流体阻滞;300和500 mm加工长度的表面质量稳定性差异不显著,但刀具磨损差异导致500 mm加工长度的表面粗糙度S_(a)和S_(z)高于300 mm加工长度。

This paper is aimed at addressing the difficulty in machining ceramic matrix composites(CMCs).The study is performed by conducting a continuous surface grinding tests on different lengths by 300 mm and 500 mm to analyze the typical damage characteristics;comprehensively evaluating the machined surface morphology by using 3D surface roughness parameters:S_a,S_z,S_(sk),S_(ku),S_(dr),and S_(bi);and systematicly studying the quality stability of the continuous surfaces with different machined lengths.The results show that the effective length after grinding exceeds 70%,yet peeling and overcut damages occur randomly.Peeling damage is due to the low bond strength at the coating-composite interface,while overcut damage is caused by minor angular errors between the ideal machined surface and the fiber braid layers.Both peeling and overcut damages can lead to the exposure of porosity in the CMC layers,the damage to surface integrity and the effect on surface gas tightness;however,there′s no pore defect expansion due to machining.Excluding the aforementioned damaged areas,the machined surface is smooth and flat,presenting a mirror-like state that can offer better load-bearing capacity and lower fluid obstruction.There is no significant difference in surface quality stability between 300 and 500 mm machining lengths,but the surface roughness values S_(a) and S_(z) of the machining length by 500 mm due to the different tool wear are higher than that of machining length of 300 mm.