纤维复合材料层合板内埋光纤光栅传感器的保护技术

Protection technology of optical fiber grating sensors embedded in fiber composite laminates

内埋的光纤Bragg光栅(FBG)传感器的存活率及测试精度是其在线监测纤维增强树脂基复合材料制备和服役状态的重要前提。采用[9011/011]的碳纤维预浸料铺层方式,在层合板0°和45°方向的典型位置埋入FBG温度和应变传感器,采用模压成型工艺制备复合材料层合板。在异向铺排(光纤光栅方向与碳纤维方向不同)的45°方向光纤光栅传感器内埋于碳纤维预浸料层间的过程中,对其采用4种不同的保护方式。通过对比实验结果发现:当对异向铺排的FBG传感器不采取保护措施时,在加热加压复合材料时光纤光栅容易失活;整层铺设同向预浸料以保护异向铺排的FBG传感器的方式改变了具有特定铺层参数复合材料的力学性能;采用窄长条同向预浸料上下包埋保护FBG传感器的方式增大了应变光栅测量结果的系统误差;采用窄长条同向预浸料上下包埋并在邻近铺层开凹槽的保护方式能明显提高内埋光纤光栅的存活率及测试精度。

The survival rate and testing accuracy of embedded fiber Bragg grating（FBG）sensors are the precondition to on-line monitor the manufacturing and working status of fiber reinforced resin matrix composites.The stacking sequence of carbon fiber prepregs is[9011/011].The FBG temperature and strain sensors were embedded into the typical positions of the laminates along 0°and 45°directions,and then the composite laminates were manufactured by compression molding method.Four kinds of methods were used to protect fiber grating sensors when they were embedded into the laminates in direction of 45°where the fiber grating direction is not parallel to the carbon fiber direction.By the comparison of the experimental results,it can be concluded that the embedded FBG sensors which were not parallel to the carbon fiber direction were easily inactivated in the hot compression molding process without any additional protection;the method of laying several whole layers of synclastic prepregs to protect the FBG sensors which were not parallel to the carbon fiber direction has changed the mechanical performance of composites with specific layer parameters;the measurement error of the strain sensors would be enlarged if two narrow prepreg strips on both sides of the sensors were introduced to protect the sensors;the survival rate and testing accuracy of the fiber Bragg gratings would be significantly improved through the method in which two narrow prepreg strips on both sides of the sensors and opening grooves on the neighboring layers were used to protect the sensors.