NCF Cross-PLY Laminates: Damage Accumulation and Degradation of Elastic Properties

Abstract

Traditionally high performance composite parts (for instance structural parts used in aerospace applications) are made by lamination of prepregs. However, multi-axial warp knitted fabric (non-crimp fabric (NCF)) proved to be a good alternative. NCF composites combine fairly good mechanical properties with low production costs, high deposition rates and unlimited shelf life. Additionally to these benefits, NCF composites have also been reported to show increasing out-of plane fracture toughness and damage tolerance [1,2]. NCF composites are manufactured from preforms with multiple layers of straight fiber bundles with different orientations stitched together by a warp knitting procedure [3] (see Figure 1a). The main difference between prepreg-tape based laminates and NCF composites is that the former has an internal structure consisting of continuous fibers that are rather homogeneously dispersed; whereas NCF composite has continuous fibers combined in fiber bundles with well defined geometry (see Figure 1b).