Composite pipelines: Analyzing defects and advancements in non-destructive testing techniques

In recent decades, various pipeline industries, such as oil, gas, and water, have increasingly focused on fiber-reinforced polymer (FRP) pipes. This growing interest in FRP pipes offers multiple advantages over traditional pipelines made of steel and concrete, including exceptional corrosion resistance, a favorable weight-to-strength ratio, reduced maintenance costs due to its durability, and customer-specific customization in sizes and strength. However, the intricate manufacturing processes and its specialized handling and installation requirements make it susceptible to defects. The traditional non-destructive testing (NDT) methods, primarily developed for metals, are inadequate when applied to FRP. It is mainly because fiberglass composites are inherently non-homogeneous and anisotropic in contrast to their metallic counterparts, introducing a unique set of challenges. As a result, the fields of Non-destructive Testing & Evaluation (NDT&E) and Structural Health Monitoring (SHM) for FRP piping systems are currently vibrant areas of research and development. The objectives of this paper are (i) to identify potential damage types in composite pipelines, (ii) to compile a comprehensive list of defects currently examined in the literature, and (iii) to present the latest progress in NDT&E techniques for composite pipelines, specifically addressing the operational constraints and practical challenges involved. Consequently, it is tailored specifically to address the needs and challenges of the pipeline sector. It is found that the state of NDT for composite pipelines is still nascent, with extensive research required to reach maturity. Critical areas for development include broadening inspection ranges, validating performance in real-field conditions, detecting, and characterizing natural defects, and improving imaging techniques. Moreover, there is a need to transition from reactive to proactive strategies in pipeline monitoring.