Structural Integrity Health Monitoring of Solid Rocket Motor Based on High Performance Ultrashort Femtosecond Grating Arrays

Composite shell damage, interface debonding, and propellant creep are the main culprits affecting the structural integrity of solid rocket motors (SRMs). There is an urgent need for real-time online monitoring of health status. Therefore, for the first time, we have designed new type of oxide-doped fiber and fabricated an ultrashort femtosecond grating array using femtosecond laser direct writing technology. Combined with multitube packaging technology, contact measurement inside the SRM has been achieved. The strain characteristics of the SRM during storage were analyzed, and the multilayer strain transfer model were constructed. An ultrashort femtosecond grating arrays with high contrast is inscribed on an oxide-doped fiber. The grating array is effectively coated. The sensor can measure temperature up to $1100~^{\circ }$ C and strain up to 14 $000~\mu \varepsilon $ . The problem of fiber sensor integration and extraction in the SRM is solved, and the survival rate reaches 95%. The strain of the actual SRM in separate processes was mastered. Combined with nondestructive testing technology, the accuracy of the sensor array for SRM damage monitoring can reach 100%. It provides key technical support for the structural integrity state monitoring of SRM.