The presentation focuses on materials test engineering for circular economy, considering circularity strategies for material life cycles. It addresses complex characteristics such as anisotropy and material degradation. Innovative in-situ testing strategies, including quasi in-situ and real in-situ approaches, are explored for fatigue loading. The study involves all-cellulose and (hybrid-) composites, aiming to optimize frequency and load for breaking stress. Overall, it sheds light on sustainable material characterization methods.