Nanoindentation test for the determination of interfacial deterioration in GFRP composites in alkaline environment

• Published in: Construction & building materials Vol. 458; p. 139722
• Main Authors: Ke, Linyuwen, Wang, Peng, Leung, Christopher K.Y.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 10.01.2025
• Subjects: Alkaline environment; Fiber-matrix interface; Glass fiber reinforced polymer (GFRP); Interfacial deterioration; Nanoindentation; Glass fiber reinforced polymer (GFRP); Interfacial deterioration; Fiber-matrix interface; Alkaline environment; Nanoindentation
• ISSN: 0950-0618
• DOI: 10.1016/j.conbuildmat.2024.139722

The mechanical properties of glass fiber reinforced polymer (GFRP) composites can be significantly affected by the fiber-matrix interface due to its large area per volume and its vital role in load transfer. The bonding at such interface, however, may be vulnerable when exposed to alkali environment mainly because of the accelerated water/ion penetration caused by the matrix hydrolyzation. In this study, a novel approach using nanoindentation is brought forward to quantitatively investigate the interfacial deterioration in alkaline environment. Cylindrical GFRP bars are fully immersed in either NaOH solutions with different pH values or distilled water (DW) under 60 °C for 360 days, followed by nanoindentation test on fibers at different distances to the edge to determine interfacial shear strength (τs) and interfacial friction (τf). Results indicate that long-term immersion in alkaline solutions can cause interfacial deterioration. Such detrimental effect of alkaline environment is more apparent (e.g., ∼ 30 % drop in τs of edge fibers with immersion in pH13 solution) than mere moist condition (e.g., ∼ 13 % drop in the counterpart immersed in DW). Results also reveal that for aged specimens, fibers with no observable interfacial damage under the microscope can also suffer from interfacial degradation, which mainly occurs at regions very close (within 1 mm) to the member surface. This study demonstrates the nanoindentation method as an applicable and sensitive approach for quantifying changes at the fiber-matrix interface. With this method, in-situ interfacial degradation of fibers inside GFRP can be determined, providing input for modeling durability performance under various environmental conditions. [Display omitted] •A novel approach with nanoindentation for interfacial degradation is elaborated.•Testing and analytical procedures are developed for interface characterization.•Interfacial deterioration in alkaline environment is quantitatively investigated.•Interfacial deterioration at intact interfaces after aging can also be captured.•Results can be further adopted in multi-scale modelling and quality control.