UV/thermal dual-cured MWCNTs composites for pipeline rehabilitation: Mechanical properties and damage analysis

Abstract

Deformation and damage in underground pipelines remain challenging to monitor over the long term due to sensor degradation caused by corrosive substances present in the pipelines. This study investigates the potential of incorporating multi-walled carbon nanotubes (MWCNTs) into ultraviolet-cured-in-place pipe (UV-CIPP) material, a widely adopted trenchless repair technique, to enhance performance and enable deformation monitoring. A UV/thermal dual-curing strategy is introduced to mitigate the significant reduction in light transmittance caused by the inclusion of MWCNTs in the composite material. The addition of MWCNTs led to a 94.86 % reduction in light transmittance through glass fibers. However, this issue was effectively resolved through the incorporation of thermal curing, allowing for the production of ultra-high-strength composites using only three layers of fibers within a short curing time. Under optimal conditions (0.2 wt% MWCNTs with the impregnation layer on top), the flexural strength and modulus reached 442.75 MPa and 15.58 GPa, respectively, marking improvements of 14.01 % and 45.2 % over the base material. Additionally, the hardness on the composite's backside increased by 10.95 % compared to the front, indicating enhanced reinforcement. The tensile strength of braided glass fibers improved by 42.31 % and 197.54 % with the addition of 0.2 wt% and 1.0 wt% MWCNTs, respectively. Failure modes varied based on the location of the sensing layer, but all specimens eventually failed due to resin cracking, delamination of the MWCNTs-impregnated layer, and fiber fractures. The UV/thermal dual-cured composite material developed for pipeline rehabilitation in this study exhibits ultra-high strength and shows significant potential for multifunctional sensing applications.