Effects of Porosity on CFRP Repair Performance with Aerospace Applications

Abstract

On-site repairs of carbon fiber reinforced polymer composites, wet layup repairs with heat blanket method play a critical and practical role for the composite defects that occur in production and assembly. The porosity level should be controlled for the repair parts with heat blanket method since the pressure value, which enables ply consolidation, reduce the risk of delamination in the composite layers, is less or zero with the wet layup repaired parts with heat blanket compared to repair parts with autoclave pressure. In this experimental study, an investigation was conducted regarding the tensile strength change of prepreg structures using wet lay-up repair techniques with heat blanket based on the porosity, with a specific focus on stepped-repaired carbon fiber reinforced polymer laminates. This work aims to understand the strength and the associated failure mechanisms of on-site repaired woven carbon fiber reinforced polymer laminates through experiments. The Automatic Ultrasonic Pulse Echo Inspection Method was utilized to see whether porosity level of each repaired samples is within allowable design limits for this purpose. Prepreg structure's repairs using wet lay-up produced according to standardized aerospace procedures were tested under uniaxial tension per ASTM 3039D. The relationship between attenuation difference (ΔdB) and tensile fracture values has been explored, with a focus on investigating the associated failure mechanisms. Initially, a 60% strength recovery was observed for repairs with an 8-decibel difference. However, as the decibel difference increased, the strength recovery gradually decreased, ultimately reaching 45.2%.

Keywords

• CFRP composite repair
• Curing methods
• FEA
• Porosity effects
• Structural health monitoring
• Tensile strength

References

1. Adeodu, A. (2015). Effect of Microwave Curing on the Tensile Property of Particulate Reinforced Polymer Matrix Composites. Advances in Materials, 4(3), 67.
2. Ahn, S.-H., & Springer, G. S. (1998). Repair of Composite Laminates-II: Models. Journal of Composite Materials, 32(11), 1076–1114.
3. Ahn, S.-H., & Springer, G. S. (2000). Repair of Composite Laminates (Issue December).
4. ASTM. (n.d.). D3039/D3039M Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials. Retrieved July 27, 2023, from https://www.astm.org/d3039_d3039m-00.html
5. Budhe, S., Banea, M. D., & de Barros, S. (2018). Bonded repair of composite structures in aerospace application: a review on environmental issues. Applied Adhesion Science, 6(1), 3.
6. Chen, J., Wang, H., Salemi, M., & Balaguru, P. N. (2021). Finite element analysis of composite repair for damaged steel pipeline. Coatings, 11(3).
7. Choupani, N., & Torun, A. R. (2022). Fracture characterization of bonded composites: A comparative study. Engineering Solid Mechanics, 10(1), 109–116.
8. Da Silva, G. R., Simamoto, P. C., Da Mota, A. S., & Soares, C. J. (2007). Mechanical properties of light-curing composites polymerized with different laboratory photo-curing units. Dental Materials Journal, 26(2), 217– 223.

9. Das, D., Pradhan, S. K., Nayak, R. K., Nanda, B. K., & Routara, B. C. (2020). Influence of curing time on properties of CFRP composites: A case study. Materials Today: Proceedings, 26, 344–349.
10. George, J. M., Kimiaei, M., Elchalakani, M., & Fawzia, S. (2021). Experimental and numerical investigation of underwater composite repair with fibre reinforced polymers in corroded tubular offshore structural members under concentric and eccentric axial loads. Engineering Structures, 227, 111402.
11. HEATCON. (2023). Composite Systems.
12. Henkel. (2023). LOCTITE® EA 9396 AERO. https://www.henkeladhesives.com/vn/en/product/industrial- adhesives/loctite_ea_9396_aero0.html
13. Hexcel. (2023). Composite Materials and Structures. https://www.hexcel.com/
14. Karaarslan, E. S., Bulbul, M., Ertas, E., Cebe, M. A., & Usumez, A. (2013). Assessment of changes in color and color parameters of light-cured composite resin after alternative polymerization methods. European Journal of Dentistry, 7(1), 110–116.
15. Kubit, A., Trzepieciński, T., Krasowski, B., Slota, J., & Spišák, E. (2020). Strength Analysis of a Rib-Stiffened GLARE- Based Thin-Walled Structure. Materials, 13(13), 2929.
16. Li, S., Sun, T., Liu, C., Yang, W., & Tang, Q. (2018). A study of laser surface treatment in bonded repair of composite aircraft structures. Royal Society Open Science, 5(3), 171272.
17. Mehar, A., Ahmed, G. M. S., Kumar, G. P., Rahman, M. A., & Qayum, M. A. (2015). Experimental Investigation and FE Analysis of CFRP Composites. Materials Today: Proceedings, 2(4–5), 2831–2839.
18. Pumchusak, J., Thajina, N., Keawsujai, W., & Chaiwan, P. (2021). Effect of Organo-Modified Montmorillonite Nanoclay on Mechanical, Thermo-Mechanical, and Thermal Properties of Carbon Fiber-Reinforced Phenolic Composites. Polymers, 13(5), 754.
19. Rabe, D., Böhnke, P. R. C., Kruppke, I., Häntzsche, E., & Cherif, C. (2021). Novel Repair Procedure for CFRP Components Instead of EOL. Materials, 14(11), 2711.
20. Sánchez-Romate, X. F., García, C., Rams, J., Sánchez, M., & Ureña, A. (2021). Structural health monitoring of a CFRP structural bonded repair by using a carbon nanotube modified adhesive film. Composite Structures, 270, 114091.
21. Solvay. (2023). FM 300. https://www.solvay.com/en/ product/fm-300
22. Sonat, E. (2021). Mechanical Properties of Repaired Carbon Fiber Reinforced Polymer Composites. Middle East Technical University.
23. Sonat, E., Bakır, M., & Özerinç, S. (2023). Failure behavior of on-site repaired CFRP laminates. Composite Structures, 311(June 2022).
24. Sonat, E., & Özerinç, S. (2021). Failure behavior of scarf-bonded woven fabric CFRP laminates. Composite Structures, 258(September 2020), 113205.
25. Tomblin, J., Seneviratne, W., Escobar, P., & Yoon-Khian, Y. (2002). Shear stress-strain data for structural adhesives. US Department of Transportation Federal Aviation Administration Office of Aviation Research, Washington, DC, Rapport technique DOT/FAA/AR-02/97.