A 70 MPa Type IV hydrogen composite pressure vessel (CPV) was instrumented with embedded Fiber Bragg Grating (FBG) sensors to realize in situ strain monitoring during hydraulic fatigue cycles. FBG arrays were co-wound with carbon fibers during the filament winding process, forming an integrated multi-point sensing network within the composite layers. Hydraulic fatigue tests were conducted under pressure cycling between 2 MPa and 87.5 MPa, reaching 48,000 cycles. The embedded FBG sensors were able to stably record cyclic strain evolution with peak amplitudes of approximately 6000 με in the hoop layer and 3500 με in the helical layer under hydraulic cycling. The hoop layers exhibited gradually decreasing strain amplitudes from the inner to outer regions, while the helical layer maintained stable signal performance. Analysis of fiber survival times indicated that the FBGs embedded in helical layers remained functional throughout the entire test, confirming the long-term monitoring capability under high-pressure oil environments. This study demonstrates a practical embedded-sensing approach compatible with the filament-winding process, providing experimental support for fatigue-life evaluation and in-service safety monitoring of high-pressure hydrogen storage vessels.

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This Communication reports limited engineering screening data on polymer liner candidates for flexible composite pipes used in oil and gas service. Three exposure conditions were considered: hydrothermal aging in superheated water, thermal-oxidative aging in dry air, and hydrocarbon-medium exposure. Superheated-water immersion for up to 1000 h, dry-air aging for 168 h, and 7-day hydrocarbon exposure were used to describe changes in tensile properties, Shore hardness, mass, and thickness. Complete replicate records were available only for the thermal-oxidative aging dataset; therefore, most hydrothermal and hydrocarbon-medium results are reported as descriptive summary data. In the recorded data, EPDM formulation CL-2-1 retained approximately 89% of its tensile strength after 1000 h in superheated water. Sample L showed a smaller mean tensile-strength decrease than Sample Z after 168 h at 150 °C in dry air. In the hydrocarbon-medium summary data, XL95A/05B-S1 showed lower mass increase and smaller tensile-strength and yield-stress decreases than PERT XRT70H across the tested temperature range. The Communication provides case-specific screening evidence and identifies the need for replicated testing, statistical analysis, longer aging series, and structural characterization before general material-selection or durability conclusions are made.

This study investigates damage evolution in a polymer-lined, fully wrapped Type IV composite pressure vessel containing artificial local defects under stepwise hydrostatic loading. A 70 MPa vessel was pressurized in 20 MPa increments to 160 MPa, while acoustic emission (AE) was monitored continuously. Ball-impact calibration established the relationship between input mechanical energy and AE waveform energy. Three high-frequency criteria based on waveform and band-limited energy ratios were used to identify fiber-fracture-related high-frequency signals, while ratios between adjacent background-energy characteristic points were used to identify background-energy oscillation (BEO). The calibration yielded a mechanical-to-AE energy conversion coefficient of 1.92354 × 10⁻⁶ with R² = 0.9707. No high-frequency signals or BEOs were detected during the 20–80 MPa holds. At 100 MPa, two high-frequency signals and four BEOs occurred, with a maximum adjacent-point ratio of 4.63, suggesting the coexistence of high-frequency responses consistent with fiber-dominated damage and continuous weak AE activity. At 140 MPa, three high-frequency signals indicated the re-emergence of localized high-frequency activity after stress re-equilibration. At 160 MPa, 23 high-frequency signals, a maximum C₁ of 1330.434, and six BEOs reflected pronounced damage-related AE activity in the composite overwrap. The combined approach captures staged damage evolution and supports AE-based integrity assessment of composite pressure vessels.