Structural performance and knockdown of AFP laminates with tow-drop gaps: PEI gap filling as a mitigation strategy
A Practical Study
R.R.K. Bahadoer (TU Delft - Aerospace Engineering)
D.M.J. Peeters – Mentor (TU Delft - Aerospace Engineering)
J.J.E. Teuwen – Mentor (TU Delft - Aerospace Engineering)
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Abstract
Automated Fiber Placement (AFP) enables the efficient manufacture of high-performance composite structures but inevitably introduces tow-drop gaps that create resin-rich regions, fibre waviness, and local strain concentrations, resulting in structural knockdown. This research investigates the feasibility of mitigating these effects by co-curing PEI into tow-drop gaps of 8552/AS4 carbon/epoxy laminates using two concepts: a continuous PEI film and discrete PEI inserts. An experimental approach comprising microstructural characterization, tensile testing, and Digital Image Correlation (DIC) was employed to evaluate manufacturing compatibility and mechanical performance. DIC analysis showed that PEI modified the local strain distribution and reduced principal strain localization, with the insert configuration exhibiting the most consistent behavior. The results demonstrate that PEI gap filling is a feasible local strain-management strategy rather than a complete solution for AFP tow-drop defects.