喷管扩散段绝热层开裂分析及预防

Failure Analysis and Process Improvement of Thermal Barrier of Nozzle Diffuser

喷管扩散段绝热层采用碳布/钡酚醛树脂和玻璃纤维布/钡酚醛树脂复合缠绕成形,粗加工后在自然存放中多件产品分层开裂。通过宏微观观察、成分分析和热分析等手段对失效件的失效模式进行了分析,结合产品浸胶、缠绕工艺开展了模拟复现试验。结果表明:碳布界面弱粘接造成层间开裂失效,预浸布预固化工序中局部游离酚含量偏高,缠绕操作引入氧化铁,固化工序中发生络合反应引起纤维表面发蓝,致使界面粘接强度降低,在内应力和切削应力综合作用下发生开裂失效。

The thermal barrier of nozzle diffuser was produced by twining carbon cloth/barium phenolic resin and glass fiber cloth/barium phenolic resin alternatively. Many products cracked due to delaminating during the process of natural storage after machining. To find out the failure cause,macro and micro observation,chemical composition analysis and thermal analysis were carried out. And simulation experiments were performed according to the process of soaking and twining. The results show that the weak bonding of carbon cloth led to interlayer cracking. Local free phenol content was higher in the process of presoaking and presolidifying,and ferric oxide was introduced during the twinning process. As a result,the fiber surface blued due to blue complexation reaction during the solidifying process,degrading the interface bonding strength. Finally,the thermal barrier cracked under internal stress and cutting stress. In accordance with this fault,prevention measures are proposed.