The deformation behaviors and mechanism of weft knitted fabric based on micro-scale virtual fiber model

As a reinforced structure in composites, knitted fabric has fully forming and large deformation behaviors that cannot be achieved by other fiber-reinforced structure due to the special loop structure formed by knitting process. Therefore, the knitted fabric and its composite are widely used in aerospace, medical and energy fields, such as satellite antenna, vascular scaffold, etc. This paper presents a novel modeling method for predicting knitted fabric deformation, that is, a virtual fiber model established at micro scale and is applied to build weft knitted model. The stress and strain distributions of repeated unit cell (RUC) and the whole fabric stretched in different directions were analyzed through finite element analysis. In addition, detailed analysis and characterization are conducted for the deformation of yarn cross section under uniaxial stretching. A 4 x 4 virtual fiber fabric model is established to verify the applicability of single loop model on the fabric scale. The mechanical properties predicted are in good agreement with the experiment, indicating the effectiveness of the virtual fiber model. Compared with traditional mesoscale models, the interaction among fibers and non-linear features of yarns under large deformation can both be well simulated by virtual fiber model, especially under large deformation.