Characterizing and modeling pending properties of multiaxial warp knitted fabrics

The bending behavior of multiaxial warp knitted (MWK) fabrics is quite different from that of plain weaves and other apparel materials. According to the bending hysteresis curves obtained from KES-FB-2 (Kawabata's evaluation system), MWK fabric bending involves not only the spreading of filaments in inserting yarns, but also the buckling of inserting yarns, which accounts for the more remarkable irregularity and nonsymmetry of MWK fabric bending hysteresis curves compared with those of plain weaves. Furthermore, the inserting yarns not completely parallel to the applied bending moment direction will undergo both bending and torsional deformation during a bending cycle. Experimental observation and theoretical study has shown that the bending paths of those nonorthogonally bent yam systems follow different cylindrical helices. In this paper, a predictive bending model proves to be applicable in assessing the bending behavior of MWK fabrics in different bending directions, and the bending rigidity corresponding to an arbitrary curvature can be calculated with this model as well. Frictional restraint within fabrics is also discussed.