The influence of in-plane fiber waviness defects on the compressive properties of quasi-isotropic (QI) carbon polyether-ether-ketone (C/PEEK) composites was investigated experimentally. Specimens with localized waviness were manufactured using a stamp forming process resulting into laminates featuring multiple wavy plies, i.e. from one to three wavy 0° plies in a 24-ply QI composite and a range of maximum waviness angle between 23° to 60°. No significant influence of the waviness was found on the global laminate stiffness. Compression tests coupled with high-speed camera monitoring were performed to study the failure process. It was confirmed that the waviness defects act as a trigger for the initiation of damage, predominantly by the kinking mechanism, resulting into an early failure and significantly lower ultimate strength than the baseline when loading in 0° direction. Furthermore, it was found that all specimens with waviness and with the same layup have a similar strength, indicating that the maximum waviness angle within the range studied in this work did not significantly influence the ultimate compressive strength. However, the presence of waviness in multiple plies clearly affected the strength. It was found that the ultimate compressive strength decreased proportionally to the percentage of plies oriented in the loading direction that is wavy.
- Mechanical testing
- Thermoplastic composites