The Parametric Research For Adhesively Bonding Patch Repaired Composite Structure Based On Fatigue Progressive Damage Theory

The carbon fiber composite is widely used in the aviation and aerospace industries because of its excellent mechanical properties.In view of this situation that the composite laminates will inevitably lead to some minor damage,the technology of the adhesively bonded repairs has important engineering significance.Because the aircraft structure is not only subjected to the static load,but affected by complex fatigue load under the working condition,the study of the residual strength of the adhesively bonded repairs in composites under fatigue load is of great practical significance.In this paper,we study the method and technique to predict the residual strength of the adhesively bonded repairs in composites under fatigue load.First of all,the APDL language is used to construct the model of carbon fiber composite,and the fatigue progressive damage analysis of the adhesively bonded repairs in composites is established in the paper.Based on the three-dimensional Hashin fatigue failure criterion,considering seven basic failure modes,which include fatigue matrix cracking,fatigue matrix compression,fatigue matrix-fiber shearing,fatigue delamination,fatigue fiber breakage and fatigue fiber compression.The material degradation model that proposed by Shokrieh is used to simulate progressive fatigue damage in composites.And a sudden drop criterion is used for the degradation of the material performance in fatigue failure unit.Secondly,the paper implements a three-dimensional failure model of the adhesive layer based on continuous dielectric damage mechanics.This damage determination model of the adhesive layer is used to simulate the failure of adhesive layer.And the reliability of the failure model of the adhesive layer is verified by comparison with the experimental data.Finally,the fatigue damage model of the adhesively bonded repairs in composites is established based on the theory of fatigue cumulative damage.The fatigue damage and residual strength of the adhesively bonded repairs in composites with different patch radius are analyzed.At the same time,the influence of patch shape,patch thickness and adhesive layer thickness on the fatigue damage and fatigue residual strength of the adhesively bonded repairs in composites is researched.The fatigue test is carried out to verify the accuracy of the theoretical simulation.The best parameters of the patch and the adhesive layer under the fatigue load are determined by the simulation and experiment.