ANALYSIS AND MODELING OF PLAIN KNITTED FABRIC REINFORCED COMPOSITES

This paper presents the analysis and modeling of elastic properties of plain knitted fabric reinforced composites. Knitted fabric is formed by interlocking of looped yarns. Knitted fabric composite is heterogen eous with impregnated curved yarns and resin rich regions. Firstly, th e three-dimensional orientation of yarns was expressed in terms of kno wn parameters of the knitted fabric; these parameters are course densi ty, wale density and impregnated yarn diameter. An analytical model na med ''cross-over model'' has been proposed. This model considers the c rossing over of yarns of adjacent loops at the interlocking region. Th e average effective elastic properties of each curved yarn were determ ined using the stress-strain relations for a lamina of arbitrary orien tation. Using classical lamination theory, the effective elastic prope rites of the yarns in the cross-over model were determined. Finally th e elastic properties of the composite were determined by combining the effective elastic properties of the curved yarns and the resin rich r egions. It has been shown that the cross-over model provides a rough e stimate of the elastic modulus of the knitted fabric composite (volume fraction of fibers, V-f = 9.5 %) by comparing theoretical predictions with the experimental results. However, it is to be noted that at hig her V-f the geometry of knit loop would be distorted thus the model ac curacy would be affected.