Effects of Hygrothermal Ageing on the Interphase, Fatigue, and Mechanical Properties of Glass Fibre Reinforced Epoxy

Abstract

Reliability and cost-effectiveness represent major challenges for the ongoing success of composites used in maritime applications. The development of large, load-bearing, and cyclically loaded structures, like rotor blades for wind or tidal energy turbines, requires consideration of environmental conditions in operation. In fact, the impact of moisture on composites cannot be neglected. As a result of difficult testing conditions, the knowledge concerning the influence of moisture on the fatigue life is limited. In this study, the impact of salt water on the fatigue behaviour of a glass fibre reinforced polymer (GFRP) has been investigated experimentally. To overcome the problem of invalid failure during fatigue testing, an improved specimen geometry has been developed. The results show a significant decrease in fatigue life for saturated GFRP specimens. In contrast, a water absorption of 50% of the maximum content showed no impact. This is especially remarkable because static material properties immediately decrease with the onset of moisture absorption. To identify the water absorption induced damage progress, light and scanning electron microscopy was used. As a result, the formation of debondings and cracks in the fibre–matrix interphase was detected in long-term conditioned specimens, although no mechanical loading was applied.

Ductility of Concrete Beams Reinforced with FRP Rebars

“…FRP is sensitive to the changes of humidity and temperature. Prolonged exposure to the outside environment can significantly reduce the durability of the element [52]. Outer elements also require anchorage, which is easier to provide for internal elements.…”

Influence of out-of-plane fiber waviness and different environmental conditionings on mechanical and morphological characteristics of fiber glass/epoxy laminates

“…It is expected that the exposure of glass fiber/epoxy resin laminates to the environmental conditioning tests (in distilled water and in saline solution) promotes the deterioration of their mechanical properties in σ max and E, since water can lead to a hydrolytic attack between their phases; thus, reducing the transfer of mechanical efforts from the matrix to the reinforcement. 31 In addition to the deleterious effect on the interface, other factors can promote a decrease in σ max and E values, such as degree of swelling of organic fibers and polymeric matrix, 32 as well as its plasticization. 33 It is also expected that specimens subjected to environmental conditioning in distilled water have lower mechanical properties at σ max and E, and greater є rup , compared to specimens exposed to saline water, since a greater mass gain in distilled water conditioning can interfere more strongly with the mechanical properties of samples.…”

Hygrothermal Damage Monitoring of Composite Adhesive Joint Using the Full Spectral Response of Fiber Bragg Grating Sensors

“…Besides swelling, the absorbed water will cause plasticization, decrease in the glass transition temperature and reduction in their mechanical strength [ 16 , 17 , 18 , 19 ]. Eventually, it will also lead to weakening of the interface and interfacial defects/cracking [ 11 , 12 , 13 , 19 , 20 , 21 , 22 ]. Elevated temperature will accelerate moisture diffusion [ 20 , 23 , 24 ] and aggravate degradation on the one hand.…”

“…Eventually, it will also lead to weakening of the interface and interfacial defects/cracking [ 11 , 12 , 13 , 19 , 20 , 21 , 22 ]. Elevated temperature will accelerate moisture diffusion [ 20 , 23 , 24 ] and aggravate degradation on the one hand. On the other hand, in thermoset adhesive with incomplete cross-linking after cure, elevated temperature may enhance post-curing which increases cross-linking and strength [ 13 , 24 , 25 , 26 ] as well as reduces volume [ 14 , 21 ].…”