Mode conversion behavior of guided wave in glass fiber reinforced polymer with fatigue damage accumulation

This paper presents a study on the mode conversion effect of guided wave in glass fiber reinforced polymer (GFRP) with fatigue damage accumulation. By using a laser ultrasonic system, a series of time-space diagrams of guided wave has been obtained, which shows the failure process of the specimen under tension-tension fatigue loading. An interesting phenomenon that the mode conversion effect becomes increasing more pronounced with the micro-damage accumulation can be observed in the experiment and further quantitatively evaluated by defining an index MMR (Mode-to-Mode Ratio). An investigation of the relationship between mode conversion effect and matrix crack density is then carried out by means of the finite element method. Influences of various factors such as the density and the randomness of the simulative matrix crack distribution are discussed. Results show that the matrix crack density makes a major contribution to the mode conversion effect in despite of the limited influence caused by the random distributions of the matrix cracks, which offers great potential for composite fatigue evaluation by using the mode conversion effect.