| Textile processes determine fabric geometry. Textile geometry determines mechanical properties. Thus, two models are developed: one is improved digital element model, which is to predict fiber level micro-geometry based upon processing mechanics, the other is fiber-matrix element model, which is to predict mechanical properties and fiber tension based upon the micro-geometry.; In improved digital element model, a fiber is modeled as a digital chain, and a yarn is an assembly of fibers within the yarn. When the distance of two digital chains is smaller than the diameter of the chain, the contact element is inserted. Then the procedure similar to FEM is conducted to simulate the textile process mechanics. Two improvements are made in this model. One is the yarn discretization, which both yarn cross-section shape and yarn path can be represented by fibers. The other is contact force modification, which allows coarse mesh of digital element, so saves a lot of computation time. It is found that 19-fiber yarn model is sufficient to represent yarn geometry and predict the mechanical properties precisely and in the simulation the initial yarn cross-section shape has little effect on the final micro-geometry.; To speed the geometry simulation process, a new static force relaxation approach is developed. It is to determine the fabric geometry based upon the initial fabric topology and the tension applied to digital chains.; Fiber-matrix element model is developed based upon the micro-geometry. In this model, fibers, which assumed as a one-dimensional entity without thickness, are embedded inside the matrix. The same displacement and shape function are applied to both fibers and matrix as iso-parametric element. Because of the compatibility of the iso-parametric element, the continuity of the fiber segment between elements will be strictly maintained. By using this model, the stiffness of composite can be calculated; fiber tension and failure can be simulated.; Four types of textile composite numerical simulation are presented. The simulated results agree well with the experimental results. Therefore, with these newly developed two approaches, one can observe the yarn path and yarn cross-section, and predict the properties of the textile composite and fiber failure processing. |
