# Extracted PDF Summary

Source: `projects/finished-projects/main.pdf`

Title: Mitigating Out-of-Plane Fiber Waviness in AFP Laminates with Tow-Gaps via Selective Placement of Thermoplastic Veils

Authors: Ahmadreza Ravangard, Kuthan Celebi, Sergii G. Kravchenko, Oleksandr G. Kravchenko

Published: Fibers 2025, 13, 145. Published 24 October 2025.

DOI: https://doi.org/10.3390/fib13110145

Keywords: automated fiber placement; fiber tow-gaps; out-of-plane fiber waviness; resin-rich regions; thermoplastic veils

## Main Extracted Information

- The paper studies automated fiber placement tow-gap defects, especially resin-rich regions and out-of-plane fiber waviness.
- The proposed mitigation method is selective placement of high-melting-temperature polyetherimide (PEI) thermoplastic veils into tow-gap regions.
- The veils act as a morphology-conditioning scaffold: they reduce ply sinking, smooth surface waviness, and reinforce resin-rich regions with an interpenetrated veil/epoxy network.
- Reported morphology improvements include peak-to-valley height variation dropping from about 0.47 mm to 0.23 mm, and resin-rich pockets shrinking from about 250-400 um to below 50 um.
- In x-direction loading, veil samples showed near recovery of tensile strength and stiffness compared with gap-only samples: strength increased from about 1300 MPa to about 1476 MPa, and stiffness increased from about 81 GPa to about 100 GPa.
- In y-direction loading, veils changed damage propagation but did not replace the missing load-bearing 90-degree fibers, so strength remained below pristine laminates.
- DIC and progressive failure analysis support the conclusion that geometry and load-path control, rather than direct fiber replacement, drive the strength recovery.
- The authors note limitations: manual layup with roller compaction does not capture all AFP deposition effects, and the numerical model used idealized gap geometries.

## Extracted Outputs

- Combined text: `text/main.txt`
- Per-page text: `text/page-001.txt` through `text/page-023.txt`
- Combined Markdown with page renders and image references: `main_extracted.md`
- Rendered full pages: `pages/page-001.png` through `pages/page-023.png`
- Embedded images: `images/`
- Machine-readable manifest: `manifest.json`
- Image manifest CSV: `images_manifest.csv`