Abstract
Carbon fiber reinforced polymer (CFRP) laminated structures are extensively utilized in critical fields such as transportation, aviation, and aerospace, owing to their superior mechanical properties. However, in practical service, these structures are susceptible to internal defects induced by environmental factors, such as matrix cracking and interlayer delamination, which significantly degrade their mechanical performance. Consequently, the effective detection of structural damage in composite materials has become a pressing issue that demands immediate attention. This study investigates cantilever bending experiments performed on CFRP laminates with pre-embedded damage, aiming to accurately identify localized structural damage. An fsFBG sensor, composed of six serially connected gratings, was mounted along the centerline of the CFRP laminate surface to capture strain response data from multiple measurement points. Through systematic analysis and comparison of the collected strain data, this research explores the influence of diverse damage locations and types within CFRP laminated specimens on surface strain patterns and confirms the linear strain response characteristics of the fsFBG sensor. The results indicate that both matrix cracking and interlayer delamination damage cause a significant increase in strain near the fixed end of the cantilever beam. Specifically, matrix cracking within the 0° layer and delamination between the [0/45] layers exhibit the most pronounced effects on the strain response. Further curve fitting of strain data for different damage types shows that positive and negative coefficients can effectively distinguish the specific characteristics of interlayer delamination and matrix crack damage. This finding provides a theoretical basis for reverse identification of damage locations. Moreover, the study demonstrates the effectiveness of fsFBG sensors in detecting the location and type of internal damage within CFRP laminates, offering novel references for structural health monitoring and damage assessment in relevant fields.

Key words: Carbon matrix cracks; Interlayer delamination; Damage detection; fsFBG sensor; Cantilever bending experiment