Material Modeling And Thermoforming Process Investigation Of Carbon Woven Fabric Composites

Fiber reinforced composites have been widely used in such fields asaerospace, defense and wind power industries. However, fiber reinforcedcomposites manufacturing usually has product defects such as tearing,wrinkling and debonding during thermoforming and technical defect suchas a long process cycle. The high manufacturing cost has limited theirapplication in high volume merchandises such as automotive industry. Sowith the financial support of national science fund (project item:50975236,11172171), the paper shows a systemic and in-depth study by focusing onthermoforming of carbon woven fabric composites.By tensile and picture-frame experiment, basic mechanical data ofcarbon woven fabric composites have been accumulated. Based on fiberreinforced continuum mechanics theory, an anisotropic hyperelasticconstitutive model is developed to characterize the anisotropic nonlinearmaterial behavior of woven composite fabrics under large deformationduring forming. The strain energy function for the anisotropic hyperelasticmodel is decomposed into the tensile energy from weft and warps yarnfiber stretches and shearing energy from fiber-fiber interaction betweenweft and warp yarns, respectively. The strain energy can approximativelybe equivalent to the deformation energy without considering unloading.Thus engineering application model was easily deduced. Model parameterscan be characterized just by basic mechanical experiments, which makethe proposed model convenient for industrial applications.Using FORTRAN language, based on the user-defined subroutineUANISOHYPER_INV of general purposed nonlinear finite elementanalysis software ABAQUS/Standard to code the proposed model forcarbon woven fabric composites, numerical simulations of stamping deformation with a hemisphere punch and double dome are implemented,respectively. Comparisons between these numerical results and the actualexperimental data have proved verification and efficiency of the proposedmodel.Finally, by combining carbon woven fabric with thermoplasticspolypropylene (PP) grains, a thermo-stamping process is proposed forforming parts with complex double curvatures in one step, to implementthe affordable application of fiber reinforced composites in automotiveindustry. In the proposed thermo-stamping process, a laminated carbonwoven fabrics with PP grains is heated by a heating furnace, and thentransferred rapidly to a hot stamping mould for thermo-stamping, andcooled down on-situ with pressure to form the carbon fiber reinforcedcomposite part. A simulation of this thermoforming experiment by usingthe proposed model was implementing. Comparisons between simulationresults and experimental data show that the proposed anisotropichyperelastic model can effectively characterize the anisotropic materialbehavior of woven composites under large deformation. The developmentof this anisotropic fiber reinforced anisotropic hyperelastic model iscritical to the numerical simulation and processing optimization of wovencomposites forming.