Effect of thermal aging on the microscale mechanical response behavior of glass fiber/epoxy composites.

This work aims to evaluate the effect of thermal aging on the microscale mechanical properties of glass fiber-reinforced plastics (GFRP) composites in three typical media environments of oil and gas fields. These include circulating air, simulated produced water, and simulated oil. A nanoindentation technique was employed to partition the indentation locations in the microstructure of the GFRP composites in order to assess the decay of the elastic modulus of the fiber and polymer matrix phases, the bond strength of the matrix, and the changes in viscoelastic behavior. The deterioration in the mechanical properties of GFRP materials following exposure to the aging process is investigated in conjunction with the Barcol hardness test, with observations and verification conducted via SEM. The test results demonstrate that the modulus increases from 2.73 Gpa in the pure resin region to 15.88 Gpa in the restrained region. This is attributed to the restraining and reinforcing effects of the fibers in the unaged samples. Additionally, it was determined that the GFRP material exhibited had the highest sensitivity to the hydrothermal environment, with notable effects on the outer resin and fiber/resin interfaces. This resulted in a 55% reduction in interfacial strength. The next most significant factor was the sensitivity to the thermal-oxygen environment, which resulted in a more pronounced reduction in fiber strength, amounting to a 18.3% decline. The oil-heat environment did not exert a notable influence on the overall performance of the GFRP material. Nevertheless, the hydrothermal and oleothermal environments result in the plasticization by degradation of the polymer network, which alters the damage mechanism of the surface resin and transforms brittle damage into plastic deformation. [ABSTRACT FROM AUTHOR]