Impact Damage Behavior and Non-Destructive Inspection Methods of Thin Hybrid Carbon-Flax Laminates

This work investigates the use of flax fibers in aerospace applications, focusing on the properties of impact energy absorption and non-destructive testing (NDT) methods in terms of greener aerospace and good energy absorption properties. The specimens investigated were double layered woven fabrics made of carbon (C) and flax (F). The materials were carbon, plain weave, 200 g/m^2 and flax, twill weave, 100 g/m^2, 150 g/m^2 and 200 g/m^2. Laminates were fabricated with a vacuum infusion technique using an epoxy bio resins glue (Super Sap), which is 19% bio-based. The quality of the fiber-matrix bonding within the different laminates was analyzed with the imaging technique computer tomography. The analysis of impact damage was performed on energy dissipation, optical appearance, depth and size. In order to identify the damaged area within the material and find out about the applicability, the NDT methods "Ultrasonic Echo Analysis" and "Vibration-Induced Thermographic Inspection" were attempted. The results showed that of the three flax weaves, the 150 g/m^2 flax weave performed the best mechanically in hybrid and pure laminates. Furthermore, the stacking sequence of the hybrid laminates showed an effect on the damage behavior, as [C/F] laminates showed small damage up to 1.5 J, while [F/C] specimens were damaged completely. The Ultrasonic Echo Analysis was applied to pure flax and hybrid specimens, with acceptable interpretability. Vibration-induced thermography was barely interpretable, but showed better results when filming the carbon side of the hybrid specimens.     «

This work investigates the use of flax fibers in aerospace applications, focusing on the properties of impact energy absorption and non-destructive testing (NDT) methods in terms of greener aerospace and good energy absorption properties. The specimens investigated were double layered woven fabrics made of carbon (C) and flax (F). The materials were carbon, plain weave, 200 g/m^2 and flax, twill weave, 100 g/m^2, 150 g/m^2 and 200 g/m^2. Laminates were fabricated with a vacuum infusion technique...     »