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

Dennis Gibhardt,Bodo Fiedler,Audrius Doblies,Lars Meyer

doi:10.3390/fib7060055

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.

Highlights

IntroductionAs the application of fibre reinforced polymers (FRPs) in structures subjected to challenging environmental conditions like humidity, moistness, salinity, or changing ambient temperatures has been increasing for years, there is a special interest in research on this topic
The results show a significant decrease in fatigue life for saturated glass fibre reinforced polymer (GFRP) specimens
As the application of fibre reinforced polymers (FRPs) in structures subjected to challenging environmental conditions like humidity, moistness, salinity, or changing ambient temperatures has been increasing for years, there is a special interest in research on this topic

Summary

Introduction

As the application of fibre reinforced polymers (FRPs) in structures subjected to challenging environmental conditions like humidity, moistness, salinity, or changing ambient temperatures has been increasing for years, there is a special interest in research on this topic. In other areas, such as the offshore and marine industries or when pipelines are used, the long-term properties of the composite materials can be important when exposed to water or extreme humidity. A large number of application areas means that knowledge about different material properties is important. In this active research topic, many questions remain unanswered, a large number of studies have already been carried out. The obtained results suggest that a couple of complex mechanisms act on the three constituents of the composite, namely, the Fibers 2019, 7, 55; doi:10.3390/fib7060055 www.mdpi.com/journal/fibers

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Results

Conclusion