A Model For Failure Prediction Of A Composite-Metal-Weld Joint

The joints of combining composite laminates and metals are widely used in aerospace structures. Conventional means of joining are available: mechanical joining and adhesive bonding. A new kind of connection called composite-metal-weld joint is researched in this paper. And the main contents of this paper are summarized as below:1.A macro-micro model for the prediction of the strength and failure modes of comeld joints subjected to static tensile loading was developed due to the periodical characteristic of protrusions. And the method was proved to be available.2.The definition of representative volume element(RVE) was introduced. A suitable RVE was selected according to the distribution of protrusions. The unit cell model of a protrusion layer was established and a unified periodical boundary condition was applied to the model. The average stiffness of the protrusion layer was obtained by FEM.3.The strength and failure modes of the unit cell were analyzed based on the cumulative damage theory. In this paper the failure criterion used for composite was 3D Hashin criterion and the stiffness degradation model was established by user defined material USDFLD. The metal uses Von·Mises yield criterion and shear-damage failure model. The failure of interface between metal and composites was ignored because the failure of composites was the primary failure mode of comeld joints other than failure of interface and the property of interface was difficult to determine due to the complex winding state of fiber around the protrusions.4.Equivalent material parameters of the protrusion layer were then applied in the whole models to obtain the tensile strength and failure modes of the joints. The results show that the strength and failure modes of the comeld joints are affected by the density and height of protrusions, lap size of the joints and so on. The comeld joints could have higher strength by adjusting parameters.5.The macro-micro method was applied to protrusion-bolt mixed joints to predict the failure modes and load capability of mixed joints.