Fatigue Life Prediction Of LRWBCA Wing Structure Composite Elements

The fatigue life evaluation of laminated composite structures is important problem in aircraft design.Research has shown numerous models and equations used for metals and composites fatigue analysis but they are usually limited to prediction of coupon tests.This scientific work aims to present a set of equations and models to develop a single fatigue life evaluation method suitable for aircraft composite structural elements analysis requiring less amount of tests and ensuring satisfactory accuracy.Based on a review of literature,models are selected and substantiated to use in the proposed method.The method includes such components as Mandell equation as Fatigue Curve Approximating Expression,Beheshti-Harris-Adam equation as Constant Life Diagram and Howe and Owen model as damage accumulation model.Validation of the technique was carried out for standard open-hole composite specimens made of AS4/3506-1 carbon/epoxy with quasi-isotropic layup.The results of fatigue tests with constant amplitude spectrums and complex quasi-random spectrums are obtained from literature.The resultant technique is used to estimate a fatigue life of the wing designed during the work based on weight and size characteristics for longrange wide-body civil aircraft(LRWBCA).The Transport Wing Standard Test(TWIST)is used as fatigue load spectrum subjected to the wing.The results showed that the obtained method is applicable for fatigue analysis of aircraft structural elements.Finally,the technique might be useful as the way for basic evaluations on first stages of aircraft design,for scaling of elements made of composite materials etc.At the same time,the technique allows some simplifications that make it necessary to provide additional research to make it applicable for accurate calculations and structure validation.