Lubricant delivery and transfer-film formation govern friction and wear in enclosed sliding contacts, yet these buried interfacial processes are difficult to monitor. Oil-loaded microcapsules can supply lubricants to self-lubricating fabric composite liners, but their release behavior is usually optically silent. Here, we report an optically self-reporting microcapsule strategy for AF/PTFE fabric composites, in which dodecyl-chain-modified carbon quantum dots (CQDs-C₁₂) were dispersed in PAO4 and encapsulated in SiO₂ microcapsules as fluorescent lubricant reservoirs. During ball-on-disk sliding, local contact stresses triggered the release of CQDs-C₁₂/PAO4 into the wear track. The normalized integrated fluorescence area provided a semi-quantitative optical indication of the cumulative release and accumulation of the fluorescent lubricant phase. The optimized CD–MCs /Fabric achieved a friction coefficient of 0.085 and a wear volume of 1.03 × 10^-10 m³, which were 61.7% and 44.5% lower than those of Pure Fabric, respectively. SEM/EDS, Raman, XPS and cross-sectional FIB-TEM analyses confirmed the formation of a continuous multi-component tribofilm on the steel counterpart, which reduced direct fabric/steel contact and interfacial shear. This work couples optical release reporting with tribofilm-mediated lubrication, providing a route toward observable self-lubricating fabric composites for enclosed sliding contacts. 

In recent years, Fiber-Reinforced Polymer (FRP) composites have seen a significant increase in their application scope due to their exceptional mechanical properties and remarkable weight advantages. However, due to their intricate damage modes, it is crucial to employ advanced damage characterization methods to mitigate potential catastrophic consequences. Currently, a wide range of Non-Destructive Testing and Evaluation (NDT&E) techniques have been extensively employed in the damage detection of FRP composite. These techniques have undergone continuous development and enhancement, enabling reliable structural examination, particularly in the aerospace industry. This article will initially provide a comprehensive overview of the latest advancements in non-destructive testing techniques within the FRP composite material damage diagnosis, providing intensive analysis and evaluation of ten NDT technologies, namely acoustic emission test, ultrasonic test, Infrared thermography test, shearography test, digital image correlation test, eddy current test, terahertz imaging test, microwave test, electrical tomography imaging test and X-ray test, assessing the advantages and limitations of each technique. Subsequently, based on specific criteria, these non-destructive testing techniques will be assessed. However, as single non-destructive testing techniques struggle to achieve unified functions such as defect identification, localization, classification, and evaluation, a combination of non-destructive testing is proposed as a solution to achieve enhanced outcomes in practical engineering applications.