The effect of inter-ply sliding was investigated for multi-ply Non-Crimp Fabric (NCF) preforms during the Double Diaphragm Forming (DDF) process. A Finite Element (FE) model was employed to investigate the influence of the ply layup sequence and the coefficient of friction between fabric-fabric and fabric-diaphragm interfaces. Simulation results indicate that in-plane fibre compression, caused by dissimilar shear deformation between adjacent plies, can lead to out-of-plane wrinkles, where the wrinkle length is a function of the relative fibre angle at the ply-ply contact interface. The most severe wrinkles occurred when the inter-ply angle was 45° for a multi-ply biaxial NCF preform with a pillar stitch at 45° to the primary yarns. A second parametric study was conducted by incrementally reducing the coefficient of friction at the ply-ply interface. Experiments confirmed that out-of-plane wrinkles are sensitive to the friction resistance between NCF plies and therefore lubricating the fibres can minimise wrinkling defects caused by dissimilar inter-ply deformation.

在双隔膜成型 (DDF) 过程中，研究了多层非卷曲织物 (NCF) 预制件的层间滑动效果。采用有限元 (FE) 模型来研究铺层顺序的影响以及织物-织物和织物-隔膜界面之间的摩擦系数。模拟结果表明，由相邻层之间不同的剪切变形引起的面内纤维压缩会导致面外皱纹，其中皱纹长度是层与层接触界面处相对纤维角度的函数。当多层双轴 NCF 预制件的层间角度为 45° 时，具有与主纱线成 45° 的柱式针迹的层间角度发生最严重的皱纹。第二个参数研究是通过逐渐降低层-层界面的摩擦系数来进行的。实验证实，面外皱纹对 NCF 层之间的摩擦阻力敏感，因此润滑纤维可以最大限度地减少由不同层间变形引起的起皱缺陷。