Evolution of the Mechanical Properties of Recycled Glass Fibers During Pyrolysis–Oxidation of Waste Wind Turbine Blades

ABSTRACT

Pyrolysis is a promising route for recycling decommissioned wind turbine blades, but resin‐derived residues and thermal exposure can damage recovered glass fibers. This study investigated the surface morphology, fracture characteristics, and mechanical‐property evolution of recycled glass fibers during coupled pyrolysis–oxidation treatment. Pyrolysis at 500°C effectively decomposed the epoxy matrix but generated carbonaceous deposits and surface defects, reducing the mean tensile strength from 2969.54 to 2151.52 MPa. The Weibull modulus decreased from 6.05 to 5.46, indicating a tendency toward increased strength scatter. Subsequent oxidation at 300°C–500°C resulted in non‐monotonic changes in fiber strength. Oxidation at 350°C produced the highest Weibull modulus of 9.30 and the most concentrated strength distribution, whereas oxidation at 400°C produced the highest mean tensile strength of 2724.92 MPa, corresponding to 91.7% of the original‐fiber strength. Fractographic observations revealed characteristic mirror, mist, and hackle regions and suggested that tensile failure was predominantly associated with surface flaws. In contrast, excessive oxidation caused renewed surface deterioration and reduced the mean tensile strength to 1964.92 MPa at 500°C. These results identify 350°C–400°C as the favorable oxidation window, with 350°C favoring strength consistency and 400°C maximizing the absolute strength level.