Modifications of Fiber Surface and Resin Matrix on Enhancing Interfacial Strength of UV ‐ CIPP Materials

Ultraviolet‐cured‐in‐place‐pipe (UV‐CIPP) technology is widely used for trenchless rehabilitation of urban pipelines. However, the multilayered liner structure is prone to debonding and delamination due to weak interfacial bonding between fibers and the resin matrix. To address this issue, microdroplet pull‐out tests were conducted on glass fiber/UV‐curable resin systems to investigate the effects of fiber surface silanization and resin matrix filler modification on interfacial properties. The surface morphology, roughness, and chemical composition of glass fibers were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and x‐ray photoelectron spectroscopy (XPS). Three‐point bending tests were performed on laminated specimens to validate the translation of microscale interfacial improvements to macroscopic bending performance. The preferred curing parameters were determined as 150 s and 60 mW/cm 2 . For the three strategies, interfacial shear strength (IFSS) exhibited a non‐monotonic trend with increasing modification extent. KH560 treatment for 9 h yielded a maximum IFSS of 20.63 ± 1.63 MPa among the silane‐modified groups, accompanied by an increase in surface roughness Ra from 0.273 to 0.396 nm, as revealed by AFM, and successful silane grafting, as confirmed by XPS. For resin matrix modification, the preferred MgO content was 3.5 wt%, achieving an IFSS of 20.80 ± 1.88 MPa, while the preferred nano‐SiO 2 content was 3 wt%, achieving an IFSS of 22.70 ± 1.39 MPa. The bending tests confirmed that enhanced interfacial bonding translated into improved flexural performance, with the ranking of reinforcing effectiveness consistent with the microscale results.