Multi-property mechanical degradation mechanisms and reliability assessment of CF/EP composite for hydrogen storage tank winding layers after fire exposure

This study investigated the residual mechanical properties and degradation mechanisms of carbon fiber/epoxy (CF/EP) composites in the winding layer of hydrogen storage tanks (HSTs) after fire exposure. With increasing heat flux (30, 50, 100 kW/m 2 ), tensile strength decreased by 47.6 %–54.7 %, flexural strength decreased by 58.7 %–96.5 %, and shear strength decreased by 88.9 %–98.1 %. Strain evolution was captured using digital image correlation (DIC), revealing a shift in mechanical failure mode from brittle to ductile after thermal damage. Correspondingly, at 100 kW/m 2 , the tensile modulus decreased by 29.6 % and the flexural modulus decreased by 84.8 %. The results of Weibull statistical analysis showed that shear strength exhibited the most severe and concentrated degradation, reducing to 5 % of its original value, followed by flexural (14 %) and tensile strength (46 %). This work provided critical experimental data and reliability insights for improving safety standards and post-fire evaluation protocols of HSTs. • After 300 s fire exposure, tensile strength drops by a maximum of 54.7 %. • Flexural and shear strengths are more sensitive to thermal damage than tensile. • Failure mode changed from brittle to plastic before and after flame exposure. • Weibull shows a 63.2 % failure risk at bearing 46 % of the initial tensile strength.