Fatigue performance evaluation of bistable composites at different combinations of loading and environmental conditions

Abstract

Bistable composite laminates have large-scale applications in morphing and energy-harvesting structures, but their fatigue performance remains largely unexplored. This study investigates the stiffness and damage progression and evaluates bistable performance to develop protocols for long-term applications. We analyze the effects of displacement-controlled fully reversible high cycle fatigue-loading on stiffness, damage, curvature, and snap-through load in the out-of-plane loading direction at eight different combinations of parameters with frequency from 1 to 10 Hz, two boundary conditions, and temperature from 22°C to 150°C up to 3 to 10 million cycles. Stiffness and damage evolution analysis demonstrate the first two stages in out-of-plane fatigue loading. The study proposes a damage definition in terms of load adapting with two fatigue damage models: (1) Shiri Model and (2) Wu Model, while both models exhibit reasonable accuracy in predicting damage for the first two stages despite deviating at the final cycle due to assuming this cycle as the final failure cycle. Of the two models, the Shiri model provided a smaller range of model parameter values, 0.22 and 0.43, for parameters p and q, respectively, which reflects adjustability to different test conditions by maintaining a moderate range. Specimens encountered no final failure by fiber breakage and did not lose bistability for any combination. Curvature and snap-through load measurements have not substantially changed due to fatigue loading. These findings confirm application protocols with a broad range of parameters for which the laminates can operate without significant fatigue damage and maintain their bistable performance for an infinite lifetime.

A review on reprogrammable bistable structures

“…The stiffness and damage progression of a bistable composite laminate was investigated and bistable performance was evaluated to develop protocols for long-term applications. Furthermore, the effects of reversible high cycle fatigue-loading on stiffness, damage, curvature, and snap-through load in the out-of-plane loading direction were analyzed [77]. Additionally, the foldingunfolding cyclic behavior of a bistable composite tape-spring was examined, revealing that the folding peak stress decreases with the folding cycles [78].…”

“…However, the effects of material properties such as elastoplasticity, viscoelasticity and creep on the properties of reprogrammable bistable structures remain unclear, requiring further study. Exploring new materials or treatments that can enhance the durability of reprogrammable bistable structures may reduce fatigue problems caused by continuous drive and regulation [77]. Materials with inherent flexibility, self-healing properties, or enhanced wear resistance could offer solutions to these issues [173].…”