植入碳纤维蜂窝夹芯结构的光纤光栅热载荷响应光谱研究

针对航天领域复合材料结构在空间服役环境的热响应监测需求，研究了一种热载荷作用下基于光纤Bragg光栅(FBG)反射光谱特征分析的碳纤维蜂窝夹芯结构监测方法。将光纤Bragg光栅传感器分别植入碳纤维蜂窝夹芯结构的不同铺层，通过监测不同热载荷下各铺层位置的光纤光栅反射光谱，得到碳纤维蜂窝夹芯结构相关铺层位置热应变特征。研究表明，碳纤维蜂窝夹芯结构不同材料铺层的热应变特征存在一定差异。植入外蒙皮表面与玻璃布之间的光纤光栅反射光谱随着温度升高，中心波长向长波方向漂移，且波形未出现明显改变。埋植于外蒙皮第二、三层碳纤维织物预浸料之间的光栅反射光谱随着温度降低逐渐出现旁瓣、多峰等啁啾效应，其主峰与右侧次峰中心波长均向短波方向逐渐漂移，主峰峰值幅度变化较小，温度灵敏度约为5.56×10-3 dBm·℃-1，而右侧次峰幅度显著增大，温度灵敏度约为40.32×10-3 dBm·℃-1；埋植于内蒙皮和蜂窝芯子之间的光栅反射光谱随着温度降低，其半波峰带宽逐渐增大，变化率约为3.19 pm·℃-1，且出现显著多峰趋势，这是由于层间热应力分布不均匀所形成。在-70~+60 ℃温度范围，各植入层热应变均随温度升高而增大，且变化趋势相接近，而在+60~+120 ℃温度范围内，各植入层热应变变化趋势呈现显著差异。这些特性能够为后继空间环境复合材料航天器结构状态在轨监测提供有益帮助。

Research on Thermal Load Response Spectrum of FBG Sensors Implanted in Carbon Fiber Honeycomb Sandwich Structure

In the aerospace field,aiming at the requirements of thermal response monitoring of composite structures in space service environment,a monitoring method for carbon fiber honeycomb sandwich structure based on fiber Bragg grating (FBG) reflection spectrum characteristics analysis under different thermal loads was studied.The fiber Bragg grating (FBG)sensors were implanted in different layers of carbon fiber honeycomb sandwich structure respectively.By monitoring the fiber Bragg grating (FBG)reflection spectrums of each layer under different thermal loads,the associated thermal strain characteristics of the honeycomb sandwich structure can be obtained.The results show that,certain differences exist in the thermal strain charac-teristics of different material layers in the carbon fiber honeycomb sandwich structure.As the temperature increases,the center wavelength of reflection spectrum of fiber Bragg grating (FBG)implanted between the outer skin surface and the glass cloth shifts to the long wave direction and the waveform of the obtained reflection spectrum changes insignificantly.As the tempera-ture decreases,the reflection spectrum of fiber Bragg grating (FBG)implanted between the second and the third layers of the carbon fabric prepreg appears chirp effects gradually,such as sidelobe,multi-peak,etc.The main-peak center wavelength and the right sub-peak center wavelength of the reflection spectrum both shift to the short wave direction gradually.The peak ampli-tude of the main-peak does not show significant change and its temperature sensitivity is about 5.56×10-3 dBm·℃-1.The peak amplitude of the right sub-peak increases significantly and its temperature sensitivity is about 40.32×10-3 dBm·℃-1. The full width at half maximum(FWHM)of reflection spectrum of fiber Bragg grating (FBG)implanted between the inner skin and the honeycomb core increases gradually at a rate of 3.19 pm·℃-1 with the temperature decreasing.The reflection spectrum appears a multi-peak trend significantly due to the uneven thermal stress distributed between the layers.The interlaminar ther-mal strain of each implanted layer increases in similar trends within the increasing temperature range of -70 ℃ to +60 ℃.But at the temperature range of +60 ℃ to +120 ℃,the changing trend of the interlaminar thermal strain between each implanted layers shows significant differences.These characteristics can provide useful help to the following on-orbit status monitoring of composite spacecraft structure in space environment.