Influence Of Joint Mode On Tension Failure Behavior Of CFRP Laminate Joints

Composite joints are frequent and critical parts in composite structures such asaircraft structures. Therefore the design and analyze are very important. In addition,as the weight and cost of composite joints has become a large portion of aircraftmanufacturing and joint parts are easily broken, the design and analyze have caughtmuch more attention. Composite joints have special failure mode, which is differentwith metal in damage propagation characteristics and fracture properties. Thisproblem of composites joints makes the design process more difficult, so it isnecessary to analyze the failure problem, reduce the influence of unfavorable factorsand improve the efficiency and reliability of connection.In this paper, the finite element model of CFRP composite laminate wasestablished by ABAQUS. Three kinds of samples including mechanical joint,adhesive joint and mixed joint were simulated by the method of locally failuredetermination. The load-displacement curve of the connection fittings were got, theload bearing and destruction during the tensile test were predicted. At last, the axialtensile test of three kinds of connection fittings has been compared with the result ofthe finite element modeling.The research shows that: the load and displacement of the three kinds of jointspecimens show a linear relationship under tensile load; the failure load ofmechanical joint test piece can reach about200kN; adhesive failure test load issmaller relative to mechanical joint, which is about130kN; the failure load of mixedjoint test piece is about180kN. Under tensile loading, strain of the two lateral rowsof mechanical joint can reach the maximum, which is-8000με; maximum strain ofadhesive joint appears in the vicinity of adhesive end, which is5000με; theoutermost nail of the mixed joint area bear more load. The main failure mode ofmechanical joint and mixed joint are nail hole compression and tensile, occurred inthe outermost row of nail near bonding; The failure mode of adhesive test is theinterlaminar shear failure. Experimental load displacement curves is similar to thesimulation results, and the loading condition is close to the results of finite elementanalysis, which shows that, the finite element model can simulate the test morerealistic.