REDUCING OUT-OF-PLANE FIBER WAVINESS IN AFP LAMINATE WITH TOW GAPS BY SELECTIVE PLACEMENT OF THERMOPLASTIC VEILS

Fiber tow gaps and overlaps formed during the Automated Fiber Placement (AFP) process pose a major concern by introducing non-uniform composite morphology, often evidenced by resin rich regions and fiber waviness. These defects arise when deposited fibers sink into gap regions during consolidation, and their location and shape are determined during the path planning stage. From a design and structural reliability standpoint, the localized out-of-plane waviness and resin pockets can lead to premature failure. This study explores how high melting temperature thermoplastic veils, specifically Polyetherimide (PEI), can be integrated into fiber tow gaps to prevent ply sinking and mitigate fiber waviness on both the interior and exterior surfaces of the composite. Additionally, PEI veils reinforce resin rich regions by creating an interpenetrated network of high fracture toughness material within the brittle epoxy matrix. Tensile tests on cross-ply laminates with staggered gaps reveal that incorporating PEI veils alters the failure mode. The potential for selective placement of these thermoplastic veils in AFP manufacturing offers a promising route to address fiber tow gaps and enhance overall composite performance.