Modelling the forming mechanics of engineering fabrics using a mutually constrained pantographic beam and membrane mesh

Keywords: A. Fabrics/textiles B. Mechanical properties C. Finite element analysis (FEA) D. Mechanical testing a b s t r a c t A method of combining 1-d and 2-d structural finite elements to capture the fundamental mechanical properties of engineering fabrics subject to finite strains is introduced. A mutually constrained pantographic beam & membrane mesh is presented and simple homogenisation theory is developed to relate the macro-scale properties of the mesh to the properties of the elements within the mesh. The theory shows that each of the macro-scale properties of the mesh can be independently controlled. An investigation into the performance of the technique is conducted using tensile, cantilever bending and uniaxial bias extension shear simulations. The simulations are first used to verify the accuracy of the homogenisation theory and then used to demonstrate the ability of the modelling approach in accurately predicting the shear force, shear kinematics and out-of-plane wrinkling behaviour of engineering fabrics. The large deformation mechanics of biaxial engineering fabrics and viscous advanced composite prepregs are of considerable interest due to the importance of sheet forming processes for the manufacture of advanced composite products and structures. The success or failure in forming a given geometry and the properties of the final composite component are in large part determined by a material's large deformation mechanics and consequently, a significant amount of time and effort has been devoted to charac-terising and modelling these mechanics with the ultimate aim of predicting and optimising forming processes using virtual design technologies. Six fundamental mechanical properties dominate the deformation of engineering fabrics and advanced composites during forming: The tensile properties along the two fibre directions. The (trellis) shear resistance of the sheet. The out-of-plane flexural modulus of the sheet. The in-plane flexural modulus of the sheet. The transverse compressive modulus of the sheet. The integrity/cohesion of the sheet. These properties, together with friction, and the boundary conditions applied during the forming process, determine how an engineering fabric or advanced composite will deform and will influence the generation of unwanted defects. Consequently, an important challenge is in accurately capturing these properties using a suitable combination of constitutive models and modelling techniques to conduct efficient and robust simulations. Equally important are the methods of measuring these properties for real materials; often a time consuming task that can be shortened using multi-scale predictive modelling approaches [1,2]. Generally speaking, the more realistic the modelling approach, the more …