| Carbon fiber composites have excellent properties of high strength and light weight.They are widely used in aerospace,automobile,construction and other fields.With the increasing use of carbon fiber composites,especially for some large structures,defects and damage are easy to occur in the process of production and use.The remarkable advantages of bonding repair to reduce the connection quality and avoid stress concentration have been highly valued.Therefore,many researchers have done a lot of research on bonding repair.In this paper,the original shape of the material is restored by bonding repair.While ensuring the bending strength of the specimen after bonding repair,the influence of bonding repair on the bending deflection of the specimen is studied,and compared with the intact specimen to verify the reliability of bonding repair.The main research elements of this paper are as follows:（1）The specimen is made of unidirectional carbon fiber prepreg by[0/90]4Sorthogonal ply.Two kinds of lap joints,stepped and inclined,and four lap lengths（20mm,30 mm,40 mm and 50 mm）were set up in the experiment.The three-point bending experiment is carried out on the bonded specimen,and the bending process is photographed and collected by digital image correlation technology（DIC）,the maximum bending strength and bending deflection of the specimen are obtained,and the strain nephogram and failure morphology of the specimen are analyzed.The experimental results show that under the same lap length,the maximum failure load and bending strength of stepped lap specimens are lower than those of inclined lap specimens;The bending deflection of the specimen is related to the strength and lap length.The longer the lap length,the higher the bending strength,and the smaller the bending deflection of the specimen.（2）Three different types of adhesives（ductile adhesive Araldite 2015,flexible adhesive DP125 and rigid adhesive DP270）were used to bond the inclined lap joint,and the effect of adhesive types on the bending properties of the repaired specimens was studied.Four lapping slopes（1:10,1:15,1:20 and 1:25 respectively）are selected for inclined joints,and orthogonal tests are formed with three types of adhesives.The experimental results show that the strength of the specimens bonded with ductile adhesive is the largest when the lap inclination is the same,and the specimens bonded with rigid adhesive are rigid and abrupt;The bending deflection of the specimens bonded with the three adhesives gradually decreases with the decrease of the lap angle.The bending deflection of the specimens bonded with the flexible adhesive is the most obvious,and the bending deflection of the ductile adhesive and the rigid adhesive is small.（3）Four ply angles were set in the experiment,namely[0]8S,[0/90]4S,[0/45/90/-45]2S and[±45]4S.Four lap slopes（1:10,1:15,1:20 and 1:25）were used to study the effects of lap slope and ply angle on the bending properties of bonded specimens.The experimental results show that the bending strength of the pure 0°ply specimen is high as a whole,but the repair efficiency is low.It can meet the bending strength requirements only when the lap slope is 1:25.The bending strength of the[±45]4S ply specimen is low as a whole,but the repair efficiency is high.It can meet the bending strength requirements when the lap slope is 1:15;The bending deflection trend of pure0°ply specimen is relatively gentle,and the bending deflection of[±45]4S ply specimen is the largest. |
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