Fatigue Characterization of Additively Manufactured Continuous Fiber Composites Using Traditional and Non-traditional Experimental Techniques

In light of the rapid advancements in large-scale continuous fiber-reinforced polymer (FRP) composites processed via additive manufacturing (AM) for high-performance structural applications, there is a need to assess the fatigue performance of these structures. AM is being rapidly adopted due to reduced costs and time of material processing with applications spanning aeronautics, space exploration, energy (wind turbine blades, tidal wave energy converters, and composite overwrapped pressure vessels for hydrogen storage), marine, automotive, nuclear, and consumer goods. Unlike metals, fatigue in composites is multi-modal and multiscale due to inherent material heterogeneity, anisotropy, and hierarchy. Additionally, the environment, process-induced defects, and in-service damage can drastically influence composite fatigue life. In this book chapter, a review of the state of the art in the fatigue characterization of AM-FRP composites has been presented with particular emphasis on the effect of process defects and composite microstructure/morphology on fatigue damage incipience and progression. Traditional stress-life approaches have been contrasted with non-traditional techniques such as infrared thermography, conductivity drop, and other rapid and reliable fatigue assessment techniques. Some guidelines will be presented for material design and testing to reduce the qualification and certification times for emerging AM-FRP composites.