Spatial Distribution of Flexural Performance and Analysis of Failure Mechanisms of Curved Glass Fiber‐Reinforced UV ‐ CIPP Materials

ABSTRACT Ultraviolet Cured‐In‐Place Pipe (UV‐CIPP) technology is an efficient and environmentally friendly trenchless pipeline rehabilitation method. The flexural performance of its rehabilitation materials directly affects the long‐term service reliability of the repaired pipelines. This study focuses on curved glass fiber‐reinforced UV‐CIPP liners, systematically investigating their circumferential thickness non‐uniformity and spatial distribution of circumferential and longitudinal flexural performance. The failure mechanisms were revealed using acoustic emission (AE) monitoring and microstructural characterization. The results show that due to resin flow during curing, the circumferential thickness of the UV‐CIPP liner increases from the crown (0°) to the invert (180°), while flexural strength and modulus decrease symmetrically. The longitudinal flexural performance exhibits a non‐monotonic trend of increasing first and then decreasing. AE analysis identifies three damage phases: matrix micro‐cracking (50–80 dB), fiber‐resin interface debonding (80–100 dB), and unstable fiber fracture with large energy release. Scanning electron microscopy (SEM) observations confirm that the main failure modes are fiber pull‐out, resin debonding, and interlayer delamination. This study systematically quantifies the direct influence of curvature effects on the flexural performance degradation of UV‐CIPP materials through combined experimental and theoretical analysis, establishing a theoretical foundation for optimizing UV‐CIPP curing processes and material performance.