Progressive Damage Analysis Of Bonded Composite Laminate Repaires

Advanced composites have been widely used in various fields due to their excellent mechanical properties and outstanding designability.It's inevitably that defects and damages appear druing the process of manufacturing and application,therefore,it is imperative to repair the structures to ensure the good use of composites.The repairmen and evaluation of composite structures is an important issue for application of composites.The progressive damage analysis(PDA)can effectively estimate the damage extension and ultimate strength,however researchers rarely applied this method to evaluate and repair composite structrues.There exist theoretical and experimental problems that need to be solved for application of PDA in repairmen and evaluation of composite structures.This work is concerned with the implementation of PDA into the repairmen and evaluation of composites structure,the main research contents include:Firstly,this paper presents some latest theories on the composites strength analysis and chooses the relatively accurate Zinoviev theory as basis of the stiffness degradation model.It should be noted that 2D Zinoviev theory does not apply to simulate 3D finite element model.On the other hand,there exist many parameters in the Zinoviev theory,which enhance the diffculties in the modeling,therefore this paper simplified and generalized Zinoviev theroy combined with improved 3D Hashin criterion,and propose a 3D stiffness degradation.Meanwhile,the proposed 3D stiffness degradation program is implemented to simulate the 3D finite element laminate model with a opening hole.This paper disscusses the matrix,fiber and delamination's failure process,and predicted the ultimate strength of composite laminates.The numerical calculation's results are in good agreement with the experimental data,and the validity of the 3D stiffness degradation program proposed in this paper is proved.Secondly,the adhesively bonding patch repair is a common composite laminates repair method,a 3D finite element model is established for the progressive damage analysis on the adhesively bonding patch repair of composite laminates.We use the Cohesive Zone Model(CZM)to simulate the mechanical behavior of adhesive,and judge the initial damage of the adhesive by stress intensity criterion.We predict the failure modes and ultimate strength of the repaired structure.The numerical calculation's result tallies well with the experimental data,it's verfied the accuracy of the model we had presented.Finally,the correlation coefficient of peel stress and shear stress is introduced to describe the stress distribution in the adhesive,in oder to judge the effects of different parameters on the repair effect,such as patch size,patch thickness and patch layer,some useful conclusions are draw out,the conclusions can provide reference for further design and analysis.