Preforming characteristics and defect mitigation strategies for multi-layered biaxial pillar-stitched non-crimp fabric

Here, both the single layer and multi-layered NCF hemisphere preforming are systematically conducted by ex-periments to explore the preforming characteristics. Subsequently, the strategies including the weight increase of blank holder and geometrical optimization of fabric are applied to investigate the defect mitigation. As a reference, the macro and meso wrinkles are identified to be related to positive and negative shear deformation in the single layer fabric preforming. In the multi-layered fabric preforming, the defects are more serious in ply configuration [0 degrees /90 degrees, +/- 45 degrees] than that in ply configuration [0 degrees /90 degrees ]2. Furthermore, the macro wrinkle is easier to induce the defect in the adjacent layer than the meso wrinkle. In addition, the strategy of weight increase of blank holder is effective to mitigate the macro and meso wrinkles by varying the shear deformation. Most importantly, the geometrical optimization of fabric can control the fabric tension in different layers and different hemisphere regions, and then effectively mitigate the defects induced by the interlayer interaction and shear deformation in the multi-layered fabric preforming.