Application of residual strength models to finite element analysis in fatigue life estimation of a composite wing spar

摘要

An engineering approach is proposed to assess fatigue life of an aircraft composite wing spar. Two different strength degradation models are validated using finite element simulation. Stiffness degradation data is obtained based on unidirectional coupon test results from the literature. A code in the finite element software ANSYS is written that lowers the strength and stiffness in each cycle. Stress redistribution is found in any cycle using new stiffness data, and the model is checked for failure. In order to verify the model, bending fatigue tests are carried out on an unmanned aircraft spar sample. The more accurate model is used in fatigue life assessment of the spar under service loading that is found using M1N1TW1ST algorithm. The results indicate that the proposed approach can be used for design engineers in fatigue life assessment of composite wing structures.