Title: Investigating how Peel Ply Affects Initial Conditions and Aging of Carbon Fiber Reinforced Polymer Chemistry

Authors: Joann L. Hilman and R. Giles Dillingham

DOI: 10.33599/nasampe/c.22.0045

Abstract: The need to avoid stress concentrations and machining damage to carbon fiber reinforced polymer (CFRP) materials favors adhesive bonding for composite structures. However, lack of complete confidence in current bonding processes frequently requires that primary structures be mechanically fastened. Eliminating adhesive bond failure requires an understanding of the bond process and surface chemistry along with methods to quantify the state of the surface prior to bonding. Adhesive bonding depends on some type of chemical bond formation at the interface which in turn depends strongly on the surface composition. This is affected by many factors including contamination, preparation process, and the length of time the surface is exposed prior to adhesive application and curing.
A common method of surface preparation for composite materials is peel ply removal. Peel ply is an outer sacrificial ply that is designed to create a pristine surface upon removal by tearing off a thin layer of resin. The newly exposed surface has high surface free energy causing liquids such as water to have low contact angles. Water contact angle measurements collected only a few hours after peel ply removal show significant changes indicating a chemical change to the CFRP surface. In this study we examine the effects of both peel ply composition and aging on the chemistry and bondability of CFRP surfaces. Both fresh and aged surfaces were investigated using water contact angle (WCA) measurements and x-ray photoelectron spectroscopy (XPS). The effect of these changes on bond strength were examined using a double cantilever beam (DCB) test. These changes highlight the chemically reactive state of a freshly prepared CFRP surfaces along with their sensitivity to exposure. This work informs the establishment of outtime protocols for adhesive bonding processes as well as selection of peel ply for surface preparation.

References: 1. Hart-Smith, L. ""Adhesive bonding of composite structures - Progress to date and some remaining challenges"" Journal of Composites Technology and Research 24 (2002): 133-151. 2. Banea, M. & da Silva, L. ""Adhesively bonded joints in composite materials: an overview"" Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 223, (2009): 1-18. 3. Hart-Smith, L. ""Adhesive Bonding of Aircraft Primary Structures"" SAE Transactions 89 (1990): 3718-3732. 4. Phariss, M., Flinn, B., Ballien, B., Grace, W., & VanVoast, P. ""Evaluation of Peel-ply Materials on Composite Bond Quality"" Proceedings of 37th International SAMPE Tech. Conf. Seattle, Washington. Oct 31- Nov 11, 2005. Society for the Advancement of Material and Process Engineering. 5. Parker, B. & Waghorne, R. ""Surface pretreatment of carbon fiber-reinforced composites for adhesive bonding"" Composites 13(1982): 280-288. 6. Packham, D. ""Surface energy, surface topography, and adhesion"" International Journal of Adhesion and Adhesives 23(2003): 437-448. 7. Kim, J., Kim, H., & Lee, D. ""Adhesion characteristics of carbon/epoxy composites treated with low- and atmospheric pressure plasmas"" Adhesion Science and Technology 17(2003): 1751–1771. 8. Kanerva, M. & Saarela, O. ""The peel ply surface treatment for adhesive bonding of composites: A review"" International Journal of Adhesion and Adhesives 43(2013): 60-69. 9. Backman, K. & DeVries, K. ""Free Radical Formation During Machining and Fracture of Polymers” Journal of Polymer Science A. 7(1969): 2125-2134. 10. Owens, D. & Wnedt, R. ""Estimation of the Surface Free Energy of Polymers"" Journal of Applied Polymer Science 13(1969): 1741-1747. 11. Extrand, C & Moon, I. ""When Sessile Drops Are No Longer Small: Transitions from Spherical to Fully Flattened"" Langmuir 26(2019): 11815-11822. 12. Strobel, M., Kirk, S., Heinzen, L., Mischke, E., Lyons, C., Endle, J., Poirier D. and Dillingham, D. ""Contact angle measurements on oxidized polymer surfaces containing water-soluble species"" Journal of Adhesion Science and Technology 29(2015): 1483-1507. 13. Colthup, N., Daly, L. and Wiberley, S. Introduction to Infrared and Raman Spectroscopy. New York: Academic Press, 1975. 14. Wagner, C., Riggs, W., Davis, L., Moulder, J. and Milenberg, G. Handbook of X-ray Photoelectron Spectroscopy Eden Prairie: Perkin-Elmer Corporation, 1979. 15. ASTM Standard D5528-1, ""Standard Test Method For Mode I Interlaminar Fracture Toughness Of Unidirectional Fiber-Reinforced Polymer Matrix Composites"" ASTM International, West Conshohocken, PA, 2013, DOI: 10.1520/D5528-13 16. Morgan, R., & Mones, E. ""The Cure Reactions, Network Structure, and Mechanical Response of Diaminodiphenyl Sulf one-Cured Tetraglycidyl 4,4’Diaminodiphenyl Methane Epoxies"" Journal of Applied Polymer Science 33(1987) 999-1020.

Conference: CAMX 2022

Publication Date: 2022/10/17

SKU: TP22-0000000045

Pages: 13

Price: $26.00