布拉格光栅监测不同厚度方向的固化残余应力

复合材料在固化过程中产生的残余应力会严重影响材料的使用和安全。首先在研究和测试了布拉格光栅温度和应力灵敏度的基础上,将3根光栅分别以平行于碳纤维的方向置入预浸料的上、中、下3个位置,以此获得复合材料不同厚度位置的残余应力变化情况。监测结果表明,上、下层光栅监测到的预浸料固化过程几乎完全一致,而在降温时下层的布拉格光栅残余应力则比上层的要大得多,中间层布拉格光栅在固化过程中测得的残余应力最小,但在降温过程中的热残余应力不易释放而导致最后的残余应力也较大。

The monitoring of cure-induced residual stress on different depth direction by fiber Bragg grating sensors

Residual stress formed in the curing process can greatly affect the application and safety of composite material.In this paper,the temperature sensitivity and stress sensitivity of fiber Bragg grating(FBG) were firstly investigated,and then three FBG sensors parallelling to carbon fiber were embedded into different depth direction of composite material in order to in-situ monitor the changes of residual stress.The results show that change trends of the upper FBG sensor almost stay the same with the lower one,while the lower FBG sensor displays much more residual stress than the upper one at cooling stage.The middle FBG sensor experiences the least residual stress at curing process,but it has the major residual stress at last because of residual thermal stress existing.