FBG Sensing-based Plane Strain Monitoring Analysis Of Airship Envelope

Stratospheric airship is one of the aerostat which can stay in thestratosphere by its buoyancy and maneuver of its own power. It can beused for high-resolution earth observation, and also can be used as acommunications relay platform. Therefore, it has important commercialand military value.When an airship works in the stratospheric, its envelope is vulnerableto be damaged due to some external factors such as great temperaturedifference between day and night, cosmic radiation, etc. The strain ofairship envelop can reflect the health of the it. It is, therefore, of greatvalue to monitor the envelop strain of airship.The research in this paper includes three parts. Firstly, the equation ofairship envelop Von Mises stress distribution is established. FEM (finiteelement method) and experimental method are carried out to verify thevalidity of the equation. Then, theoretical analysis of FBG-based planestrain monitoring of aerostat envelope structures is presented. A theoreticalmodel is setup by using two perpendicular fibers in the monitoring. Ananalytical formula that evaluate the relationship between the strainmeasured by FBG sensors and the real one in aerostat envelop isestablished. Meanwhile, a new FBG sensor that can measure the planestrain is designed. Finally, the real strain of aerostat envelop is affected bytwo unknown parameters, axial transfer rate KLand the radial transfer rateKR. An equation is derived to calculate the axial transfer rate KL. Then, theFEM is carried out to explore KR.The research results show that Von Mises stress can describe thestress of airship envelop. And use dual FBG sensors to monitor the airship envelop strain can eliminate the transverse effect, and achieve the accuratemeasurement of plane strain. When the length of sensor is30mm, thewidth of adhesive layer is2mm, the thickness of adhesive layer is0.02mm,the thickness of substrate layer is0.02mm, the modulus of substrate layeris300MPa, the value of axial strain transfer rate KLis close to1, and radialstrain transfer rate KRis also affected by many factors, and the value of KRremains at around0.03.This paper can provide a theoretical reference for FBG-based planemonitoring applications.