基于聚合物光纤的固体火箭发动机界面脱粘原位检监测方法研究

For the existing strain sensors' shortcomings, poor compatible with rubber-based viscoelastic material, implants can lead to stress distribution interference and disturb burning law of propellants, combining the characteristics of large yield strain and highly compatible with rubber-based viscoelastic material of polymer optical fibers, the method is proposed that polymer optical fibers are used to in-situ detect and monitor the interfacial debonding of solid rocket motor. First of all, based on fiber-coupled mode theory, the fiber grating mechanism are analyzed, polymer optical fiber grating in low-loss window are design, and the production method of polymer optical fiber grating using a femtosecond laser are explored. Combining with computer simulating and experimental testing, the relationship between grating spectrometer and strain of polymer optical fibers are analyzed. On these basis, the interfacial debonding mechanism of double isotropic viscoelastic material are deeply analyzed, the mechanical model of the crack tip of propellant/coating interface are built, and the relationship between grating spectrometer and strain of polymer optical fiber is revealed. At last, implantation method of the polymer optical fiber sensors in the interface and signal demodulating method of multi-sensor channel are mainly studied. Then a nondestructive evaluation system of interfacial bond strength of double viscoelastic material based on polymer optical fibers grating is formed. The nondestructive evaluation system will solve the bottleneck problem of in-situ detection and monitoring technology of solid rocket motor's interfacial debonding and provide a theoretical basis and method support for the health monitoring of solid rocket motor.

针对现有应变传感器基底材料与固体火箭发动机材料相容性差，植入易引起应力场分布干扰，进而扰乱推进剂燃烧规律的不足，结合聚合物光纤具有大屈服应变且与橡胶基粘弹性材料高相容性的特点，提出一种基于聚合物光纤光栅的固体火箭发动机界面脱粘原位检监测方法。首先，以光纤耦合模式理论为基础，研究光纤光栅的成栅机理，设计低损耗窗口的聚合物光纤光栅，探索基于飞秒激光器的聚合物光纤光栅制备方法。通过理论计算和数值仿真，系统分析光栅光谱随应变的变化关系；在此基础上，深入研究各向同性双粘弹性材料界面脱粘机理，建立推进剂/包覆层界面的裂纹尖端力学模型，揭示界面裂纹随材料应变的变化规律；最后，重点研究传感器在界面处的埋植方案和多传感通道的信号解调方法，形成基于聚合物光纤光栅的双粘弹性材料界面粘结强度无损评价体系，解决目前固体火箭发动机界面脱粘原位检监测技术发展的瓶颈问题，为固体火箭发动机的健康监测提供理论依据和方法支撑。

由于复合材料的工艺稳定性相对较差，使得固体火箭发动机内部异质材料的粘结面成为发动机结构中稳定性较差的部位。现有技术中的应变传感器应变范围小、安全性低、容易受外界的干扰，且与固体火箭推进剂材料相容性差、植入会影响原有结构的应力分布，难以有效实现其关键连接点的粘结失效监测。上述因素使得固体火箭推进剂关键连接点失效监测技术的发展遇到了瓶颈。本项目采用与固体火箭发动机燃烧机具有较高相容性、且具有绝对安全性的聚合物光纤制作传感器以监测其关键接触面的脱粘状况。项目执行过程中，通过理论仿真研究了粘弹性材料应变特性，为实验测试方法的制定提供了理论依据；设计出了应变能够达到60%的传感器，分辨率达到1.1%的聚合物光纤大应变传感器，并集成了相应的多通道应变监测系统。将该聚合物光纤应变传感器植入到固体火箭假药试件内部后的实验测试表明该测试系统能够在-25℃到45℃范围内满足固体推进材料的应变监测要求。另外，本项目在现有固体推进剂健康监测的研究基础上计划进一步研究固体火箭推进剂的失效机理、失效评估方案、以及分布式传感器信号解调方案，最终优化、集成一套分布式固体火箭推进剂关键连接点失效监测系统。