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In this work, the glass fiber reinforced plastic (GFRP) composite pipes used as sewerage pipes in oil and gas field environments were studied. The accelerated aging experiments were carried out under the simulated environments of three typical oil field media which including circulating air, simulated produced water and standard simulated oil. Scanning electron microscopy (SEM) was adopted to observe the microscopic morphology of the aged GFRP tubes under the three conditions. The microstructural characteristics of the aged tubes and the evolution process of internal defects were also analyzed and evaluated in combination with micro-CT technology. The attenuation pattern of the hoop tensile strength of the aged pipes was measured via the separation disk method, and the service life prediction was carried out based on the Arrhenius theory with the hoop strength as the life index. The results show that the accumulation of aging time and continuous heat input will aggravate the expansion of internal pores and cause the aggregation of small-volume defects into large-volume defects. Especially in the simulated oil environment, which has the highest sensitivity to defects. The maximum porosity reaching 1.5 % and the maximum volume of individual defects exceeding 106 μm3 after aging for 4000 h at 95 °C. The thermal aging process under the three environmental conditions had similar aging characteristics, and interfacial damage of the glass fibers was observed in all of them. The variability of hydrothermal aging is related to the hydrolytic behavior of the glass fibers, which is associated with the progressive dissolution damage of the SiO 2 network in the glass fibers, as well as the breaking of silane bonds. Thus, the hydrothermal environment had the most significant effect on the hoop tensile strength decay. Ultimately, 75 % strength retention was taken as the end-of-life indicator. The predicted service life based on the Arrhenius model for the three environments of thermo-oxygen, hydrothermal and simulated oil were 23.5, 23.1 and 28.5 years at 20 °C, and 12.2, 4.9 and 10.3 years at 40 °C, respectively. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced polymer-based composites prepared by photocuring technology offer notable advantages. However, the traditional UV curing technology faces challenges in balancing curing efficiency, penetration depth, and mechanical properties when producing high-thickness fiber-reinforced composites. This study introduced a new method for crafting thick glass fiber reinforced composites via upconversion particle-assisted near-infrared photopolymerization (UCAP). Near-infrared (NIR) radiation had superior penetration in glass fiber composites system, effectively curing of specimens exceeding 20 mm in thickness. Through micro-CT and atomic force microscopy, it was verified that UCAP specimens had fewer interfacial defects and a wider interphase, making contribution to enhanced interlaminar and interfacial shear strength. Additionally, uniform curing effectively alleviated stress concentration under external forces, resulting in a 78.5 % increase in flexural strength and a 32.1 % increase in impact toughness for UCAP specimens compared to UV-cured ones. This approach facilitated rapid outdoor curing of large-sized glass fiber composites with sustained structural stability, showcasing the potential application of UCAP in high-performance glass fiber composites rapid prototyping. • Photo curing of high-thickness glass fiber composite using high penetration NIR. • NIR cured composites exhibit enhanced interfacial performance and reduced internal defects compared to UV curing ones. • NIR cured specimens exhibit uniform stress distribution compared to UV curing specimens. • Composites cured by NIR demonstrate higher flexural strength compared to those cured using UV. [ABSTRACT FROM AUTHOR]

Aiming for obtaining flame-retardant vinyl ester resins (VER) and the composite, a kind of liquid 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO)-containing 1-vinylimidazole salt (called VIDOP) was conveniently synthesized through the neutralization of the DOPO-derived acid and 1-vinylimidazole to be applied as flame-retardant crosslinking agents of VER. Curing behaviors, flame retardancy, thermal decomposition behaviors, thermal-mechanical properties, and mechanical performance of VER materials were investigated. With 25 wt% addition of VIDOP, the modified resin (VIDOP25/VER) and their glass fiber reinforced composites (VIDOP25/VER/GF) achieved UL 94 V-0 rating with a limiting oxygen index value of 32.1% and 38.3%, respectively. Both heat release and smoke release of VIDOP25/VER and VIDOP25/VER/GF decreased compared to those of the reference sample in the cone calorimetry test. VIDOP showed flame-retardant activities in both gaseous and condensed phases for the resin, while they didn't work well in the condensed phase for the composite. VIDOP/VER presented a little lower a glass transition temperature than VER with a relatively low crosslinking density, in which 1-vinylimidazoles covalently linked with the VER chain and the DOPO-derived group attached to the resin via ionic bonds. VIDOP/VER and the composite had better mechanical properties than the unmodified sample and outperform other systems in well-balanced performance. [Display omitted] [ABSTRACT FROM AUTHOR]

We investigated the feasibility of a transversely isotropic approach to assess the strength properties during the design of a composite leaf spring. A modified Arcan test setup was developed to test the strength properties of the used non-crimp fabric based material in all orthotropic directions. Through comparisons with standardized coupon test methods for fiber-reinforced materials, a notch stress factor for tensile and shear load was derived. Our results indicate that fabric influences the material's strength, and the assumption of transverse isotropy behavior is invalid. The measured transverse tensile strength was lower by a factor of 2.2 in the out-of-plane direction than in the in-plane direction, possibly leading to a lower resistance of leaf springs against delamination. Process induced differences did not significantly affect the measured strength in the tested directions. These findings will be useful in developing leaf springs with increased fatigue resistance. [ABSTRACT FROM AUTHOR]

Polymer matrix composites have established themselves in the materials family due to their improved properties like high specific stiffness and strength, durability etc. Recycled polyethylene terephthalate (RPET) is being used as matrix material in a variety of polymer matrix composites. Composite materials based on RPET matrix, in addition to being cost effective, are also environment friendly. Use of RPET as matrix material not only reduces the consumption of virgin materials, but it also simultaneously addresses the concern regarding environmental pollution due to post consumer PET waste. This review compiles and critically analyses the efforts of various researchers regarding the influence of; different types of reinforcing materials such as synthetic and natural fibers, micro and nano fillers, blending of RPET with various virgin polymers, on the properties of composite materials based on RPET. [ABSTRACT FROM AUTHOR]

• A neural network can be trained by both experimental and theoretical data. • Experimental input data ensures better defect identification than modeling data. • Automated procedure provides characterization accuracy up to 15% by defect depth. • Experimental TSR profiles provide low scattering of characterization results. The paper describes the concept of an automated defect characterization procedure by using infrared nondestructive testing of glass fiber reinforced composite. The proposed algorithms have allowed determination of defect depth, lateral dimensions and area, as well as coordinates of defect centers. The algorithms are based on the use of the neural network trained on both experimental and theoretical temperature profiles. An acceptable for practice accuracy of defect characterization has been obtained on the experimental data (0–15% by defect depth and 26–139% by defect area). [ABSTRACT FROM AUTHOR]