Abstract: As a new material with high performance, Carbon Fiber Reinforced Polymer (CFRP) have been widely used in aerospace, new energy vehicles and other fields because of their high specific strength, specific modulus and fatigue resistance. However, it will be affected by fatigue, creep and other factors during its service, resulting in internal damage to the structure, consequently reducing the safety and reliability of the material. Nowadays, the damage detection and evaluation of CFRP has become a research hotspot. At present, acoustic emission detection technology has been widely used in the damage detection of CFRP. With its unique ability of on-line and continuous monitoring, the damage process of materials can be monitored and evaluated in real time. However, due to the complexity of damage mechanism in CFRP, there are still some problems in the correct identification of damage acoustic emission signals. For this reason, an algorithm for identifying and classifying damage signals of CFRP based on modal separation method was proposed in this paper, which could realize the modal characterization of damage acoustic emission signals of composites. First of all, based on the modal analysis results of simulated sound sources of CFRP laminate, different ranges of digital filters were designed to realize the separation of S₀ and A₀ modes in acoustic emission signals. Then, according to the modal characteristics of the single damage type signals of fiber breakage and matrix cracking, the identification and classification algorithm of damage signals was established, and its resolution to the single damage type signals was verified. Finally, the algorithm was used to analyze the in-plane bending damage signals of laminates to verify its effectiveness in the identification of complete structural damage signals of CFRP. The results show that the resolution of this algorithm in fiber breakage and matrix cracking tests is as high as 97.3% and 92% respectively, and the damage process characterization of carbon fiber composite laminates is also realized. It is proved that it can be used to identify the damage mechanism of complete structures of CFRP.

Key words: CFRP, modal acoustic emission, damage identification, Lamb wave, mode separation