Experimental evaluation of the degradation of bio-based composites under extreme conditions: Impact on mechanical performance and durability

This paper characterizes the impact of long-term cyclic hygrothermal aging behavior on mechanical properties of bio-based balsa core sandwich structures through experimental investigation of moisture diffusion cycles, moisture-induced swelling effects, degradation of bending strength and stiffness, as well as the damage modes initiated in skins, skin/core interfaces and the balsa core. The structural strength and stiffness were found to be retained at 90% of the initial state after two complete moisture absorption-desorption cycles, indicating that the elastic properties of the balsa core sandwich structure can be rapidly recovered within a 7-day desorption process. Moreover, it was demonstrated that damage mechanisms including balsa wood core shear cracks and glass fiber breakage in skins would propagate more easily due to the long-term hygroscopic aging. These findings are crucial for the development of bio-based plant fiber reinforced composite structures applied in offshore wind turbines and maritime industry to reduce their carbon footprint and contribute to a circular economy.