In this paper a process simulation will start at the level of the thermodynamic analysis with a known temperature at the surface of the part. The whole process will be simulated by a transient thermodynamic analysis to get the temperature in the part. In this step the degree of cure is computed by implementation of user Fortran routine to apply the exothermic heat flux coming from the chemical reaction. After this, the temperature results are transferred to a transient mechanical analysis. This weak sequential coupling of the thermodynamic analysis to the mechanical was chosen because the temperature has an impact on the mechanical behaviour but the mechanical deformation has no influence on the temperature. For the mechanical part the material behaviour was idealized as linear viscoelastic depended on the degree of cure and the glass transition temperature via user subroutine. The cure shrinkage of the resin is implemented using exponential strain formulation also depended on the degree of cure. The innovation of this paper, which should be demonstrated here, is the discretization of the connection between the skin and the stringer. At the beginning of the manufacturing process there will be no connection between skin and stringer. The stringer is only pressed on the skin by the applied vacuum. There will be some deformations of the stringer from room temperature to 180 deg C. During the curing the resin will shrink and lead to some deformations. After some time the resin will change the phase from rubbery to solid and establish a solid fixed connection between stringer and skin. By cooling down from the curing temperature to room temperature additionally distortions will appear. To take all these effects into account it is not possible to model the connection between skin and stringer by applying fixed connection. A method using cohesive elements are used with anisotropic cure dependent material behaviour in order to take the effect of ridged body move before curing, cure shrinkage and cured connection into account. Normally cohesive elements are used to simulate the failure or debonding of an adhesive bond. In this case it will be used the other way around. The bending polar curves are not symmetric, the laminate is not balanced. This unsymmetrical property of the laminate will lead to a distortion of the stringer. As it can be seen the main factor for the deformation comes from the shrinkage of the resin. During the curing period the stringer is not stiff connected to the skin therefore the second modeling approach using cohesive elements will lead to more accurate results.


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    Title :

    Process simulation of a CFRP composite stiffened panel using an approach of cohesive elements


    Contributors:


    Publication date :

    2010


    Size :

    10 Seiten, 11 Bilder, 1 Tabelle, 8 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English






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