Experimental Research Of Detecting Debonding In FRP Reinforced Structure By Using Sound-fiber Optical Interference

With the FRP has a wide range application in the structural reinforcement,the brittle failure of the structure due to the debonding in the interface of the FRPreinforced structures attracts people’s attention. We must find a convenient, fastand effective method to test the debonding with no damage, so that we can repairthe peeling early, it is important for structural reinforcement.In this paper, we propose to test the vibration of the FRP’s surface based onthe sound-optical interferometer and nondestructive testing method. We candetermine if there is a damage or not, and we can get the relationship between theamplitude of vibration and the frequency of the sound, and we can also get therelationship between the amplitude and the location of the excitation by usingthis method. The principle of this method is that we apply sound excitation to astationary point of the FRP’s surface or point by point, then we detect thevibration of the FRP’s surface by the optical fiber attached to the FRP plate. Theamplitude will be a sudden change in the edge of the peeling, and we can find thespecific location and size of the peeling from location of mutation.The main object of this paper is to prove the viability of this method usedfor detecting the interfacial debonding of the FRP reinforced structure throughexperiments, In the experiments, we apply the sound excitation on three differentlocation according to the optic fiber, the location of the sound is stationary, it issame to the location of optic fiber, and the distance between excitation and opticfiber is constant. Then we can get the relationship between the amplitude ofvibration and the frequency of the sound, and we can also get the relationshipbetween the amplitude and the location of the excitation. Moreover, we analyzethe effect of testability of the debonding of the FRP reinforced structure withchanging the frequency of the excitation, size of the debonding, and the shape ofthe debonding. At last, we identify if there has a debonding by using BP neu ralnetwork.Trough the results of experimental research for FRP reinforced concretebeams and slabs, the peeling damage of the FRP reinforced structures has acertain testability by the sound-optical interferometer method. For the FRP reinforced concrete slab and beam, we can detect the specific location and thesize of y debonding with different injury diameter. To find the location and thesize of the peeling, we find that the effect of detecting the location and size of thedebonding when we use the excitation with resonant frequency is better thanwhen we use the excitation with non-resonant frequency. And we can use the BPneural network to identify if there has a debonding by training the experimentaldata, which verified the feasibility of this method, the rate of the identificationreaches93%.