Calculating Fatigue Life of Helicopter Composite Blades Based on the Residual Strength Theory

This paper presents a method for calculating the fatigue life of helicopter composite material blade with residual strength theory. Builded the residual strength model, analyzed the influence of loading sequence, tensile -- compressed between the conversion and failure probability, adopt corresponding treatment plan. Using the model of residual strength, selected 19 typical flight condition, using the "rain flow counting method" load matrix, finally get the helicopter load spectrum. The composite blade dangerous section are calculated (root maximum strain), combined with every moment and centrifugal force, the flight state determined blade the stress spectrum, then according to the blade model and material characteristic parameters were calculated, results show that the residual strength decreases with the increase of flight time, and the failure probability increased with the flight time increasing. By comparison, the calculation results and full size is consistent with the experimental results, which shows the calculation is reliable.