Scarf Patch Repair Techniques And Analysis For Carbon Fiber Composite Laminates

The use of laminated composite structures has been increasing in industry, specially theaeronautical industry. However, high susceptibility to low velocity impact damage, which can occurduring the life of any kind of composite structures. The scarf patch repair is one of most commonrepair techniques carried out in composite structures. Study of the repair effect has become an urgentproblem to be settled in aeronautics.This paper is developed for studying the scarf patch repair method of composites．The mainworks are as follows：(1) In order to obtain the mechanical properties of the Celion/Larc160laminates, which provideaccurate basic data for finite element simulation, a series of basic experimental tests were conductedand different lamination angle models were designed.(2) To study the behavior of open-hole16-ply [±45/0/90]2sCelion/Larc160laminates repairedby scarf patch, a finite element analysis is performed in order to calculate the stress field of therepaired laminates based on the software ANSYS. Then the stresses are coupled with failure rules，maximal shear stress criterion for the adhesive and Tsai Hill criterion for laminates to predict thecompressive strength of repaired panels. And it is found that carefully designed scarf patch repairs canrecover more than76％of the undamaged strength．(3) The theoretical prediction was good enough agreement by comparison with the experimentaldata. Moreover, some work is done about FE modeling efficiency of repaired laminates.(4) The effect of repair parameters, such as the scarf angle，thickness of the adhesive，damagedradius，etc．on the strength of repaired structures are discussed in detail．When the repaired structureswere under unidirectional loading the optimum scarf angle is about5degree, when the repairedstructures were under bidirectional loading the optimum scarf angle is about4degree. The optimumthickness of adhesive is about0.10mm~0.14mm. For different damage forms, the best repair methodswere obtained．All of the conclusions are useful to actual repair work．...