In this study, a set of analytical methods was proposed to evaluate the reliability of composite wind turbine blades after material aging, and to improve the blade structure strength to enhance its reliability. Because, the material aging will occur when the blade is affected by the external environment for a long time, consequently, time is an extremely important factor in reliability. Therefore, it is necessary to simulate the effect of environment on materials by aging experiments, so as to obtain the relationship between time, material strength and material constant.
The reliability evaluation method used in this study is the direct integration method, which can quickly evaluate the reliability of blades degraded by materials. Because the reliability of the unmodified blade impossible be more than 98% after 20 years, it is necessary to improve the blade and then evaluate the reliability. The weight of the improved blade increased by only 8.57%, but the wind speed of buckling could be delayed by 32.47%, and the reliability could be more than 99% after 20 years, so the improved method meets the demand.