Title: Effect of Sizing on the Interfacial and Mechanical Properties of Carbon Fiber (CF) Reinforced Polyamide (PA6,6) Composites

Authors: Muhammad Iqbal, Brandon Gregoire, Nagesh Potluri, and Steve Bassetti

DOI: 10.33599/nasampe/c.19.0710

Abstract: The interfacial characteristics of the fiber-matrix interface significantly influence the interfacial and mechanical properties of fiber-reinforced polymer composites.

The interfacial properties of the fiber-resin interface can be altered physically or chemically by fiber surface treatment and sizing chemistries. These techniques may help increase the surface area and/or increase the surface functional groups on fibers, thus providing a pathway to chemical bonding between the fibers and the matrix resin. Sizing may further enhance interfacial adhesion by the formation of fiber-matrix interphase in composites. The choice of sizing is considerably dependent upon the polymer resin matrix to ensure the inter-diffusion of sizing interphase with the resin during processing. Similarly, the thickness and content of sizing on fibers also influence the mechanical and interfacial properties of the resulting composite.

Presented here are the effects of fiber surface-treatment and sizing on the interfacial and mechanical properties of carbon fiber/Nylon (PA6,6) composites. After sizing commercial grade unsized carbon fibers (CF) with nylon compatible and incompatible sizing, an investigation of the influence of sizing architecture, thickness, and content on CF in the resulting composites commenced. Extraction and thermogravimetric analysis (TGA) determined the % loading of the sizing onto the carbon fibers. Sized carbon fibers were chopped and compounded with neat PA6,6 resin to prepare injection molded test bars for the investigation of tensile and flexural properties. Interfacial shear strength (IFSS) of the CF/PA6,6 composites was determined using the single-fiber pull-out method. Composite failure modes, established by utilizing SEM fractography, compared results to carbon fibers sized with an incompatible sizing for PA6,6 resin as well as unsized CF as a control.

The results indicate that the choice of proper sizing significantly enhances the interfacial and mechanical properties of the CF/PA6,6 composite samples.

References: [1] S.-S. Yao, F.-L. Jin, K. Y. Rhee, D. Hui, and S.-J. Park, “Recent advances in carbon-fiber-reinforced thermoplastic composites: A review,” Compos. Part B Eng., vol. 142, pp. 241–250, Jun. 2018. [2] D. Mathijsen, “The black magic of carbon fiber reinforced thermoplastics,” Reinf. Plast., vol. 59, no. 4, pp. 185–189, Jul. 2015. [3] N. G. Karsli, C. Ozkan, A. Aytac, and V. Deniz, “Effects of sizing materials on the properties of carbon fiber-reinforced polyamide 6,6 composites,” Polym. Compos., vol. 34, no. 10, pp. 1583–1590, Oct. 2013. [4] S. J. Park, “Surface treatment and sizing of carbon fibers,” in Springer Series in Materials Science, vol. 210, 2018, pp. 105–137. [5] N. Raphael et al., “Surface modification and grafting of carbon fibers: A route to better interface,” Prog. Cryst. Growth Charact. Mater., vol. 64, no. 3, pp. 75–101, Sep. 2018. [6] Q. Wu, M. Li, Y. Gu, S. Wang, L. Yao, and Z. Zhang, “Effect of sizing on interfacial adhesion of commercial high strength carbon fiber-reinforced resin composites,” Polym. Compos., vol. 37, no. 1, pp. 254–261, Jan. 2016. [7] P. S. Naik, S. A. Orangalu, and N. V. Londhe, “Effect of fiber weight fraction on mechanical properties of carbon-carbon composites,” Polym. Compos., vol. 33, no. 8, pp. 1329–1334, Aug. 2012. [8] D. Zhao, H. Hamada, and Y. Yang, “Influence of polyurethane dispersion as surface treatment on mechanical, thermal and dynamic mechanical properties of laminated woven carbon-fiber-reinforced polyamide 6 composites,” Compos. Part B Eng., vol. 160, pp. 535–545, Mar. 2019. [9] N. Dilsiz and J. . Wightman, “Effect of acid–base properties of unsized and sized carbon fibers on fiber/epoxy matrix adhesion,” Colloids Surfaces A Physicochem. Eng. Asp., vol. 164, no. 2–3, pp. 325–336, May 2000. [10] R. L. Zhang, Y. D. Huang, N. Li, L. Liu, and D. Su, “Effect of the concentration of the sizing agent on the carbon fibers surface and interface properties of its composites,” J. Appl. Polym. Sci., vol. 125, no. 1, pp. 425–432, Jul. 2012. [11] X. Yuan, B. Zhu, X. Cai, S. Zhao, K. Qiao, and M. Zhang, “Effects of particle size and distribution of the sizing agent on carbon fiber/epoxy composites interfacial adhesion,” Polym. Compos., vol. 39, no. S4, pp. E2036–E2045, Dec. 2018. [12] F. Liu, Z. Shi, and Y. Dong, “Improved wettability and interfacial adhesion in carbon fibre/epoxy composites via an aqueous epoxy sizing agent,” Compos. Part A Appl. Sci. Manuf., vol. 112, pp. 337–345, Sep. 2018. [13] S. F. Zhandarov, E. Mäder, and O. R. Yurkevich, “Indirect estimation of fiber/polymer bond strength and interfacial friction from maximum load values recorded in the microbond and pull-out tests. Part I: local bond strength,” J. Adhes. Sci. Technol., vol. 16, no. 9, pp. 1171–1200, Jan. 2002. [14] S. Zhandarov and E. Mäder, “An alternative method of determining the local interfacial shear strength from force–displacement curves in the pull-out and microbond tests,” Int. J. Adhes. Adhes., vol. 55, pp. 37–42, 2014. [15] S. Zhandarov and E. Mäder, “Determining the interfacial toughness from force–displacement curves in the pull-out and microbond tests using the alternative method,” Int. J. Adhes. Adhes., vol. 65, pp. 11–18, 2016. [16] S. Zhandarov, E. Mäder, C. Scheffler, G. Kalinka, C. Poitzsch, and S. Fliescher, Investigation of interfacial strength parameters in polymer matrix composites: Compatibility and reproducibility, vol. 1. 2018. [17] S. Zhandarov and E. Mäder, “Characterization of fiber/matrix interface strength: applicability of different tests, approaches and parameters,” Compos. Sci. Technol., vol. 65, no. 1, pp. 149–160, 2005. [18] Z. Wang, X. Huang, G. Xian, and H. Li, “Effects of surface treatment of carbon fiber: Tensile property, surface characteristics, and bonding to epoxy,” Polym. Compos., vol. 37, no. 10, pp. 2921–2932, Oct. 2016. [19] J. W. Hutchinson and H. M. Jensen, “Models of fiber debonding and pullout in brittle composites with friction,” Mech. Mater., vol. 9, no. 2, pp. 139–163, Sep. 1990. [20] E. Mäder et al., “Coating of Carbon Nanotube Fibers: Variation of Tensile Properties, Failure Behavior, and Adhesion Strength ,” Frontiers in Materials , vol. 2. p. 53, 2015. [21] S. Zhandarov, E. Mäder, C. Scheffler, G. Kalinka, C. Poitzsch, and S. Fliescher, “Investigation of interfacial strength parameters in polymer matrix composites: Compatibility and reproducibility,” Adv. Ind. Eng. Polym. Res., vol. 1, no. 1, pp. 82–92, Oct. 2018.

Conference: CAMX 2019

Publication Date: 2019/09/23

SKU: TP19-0710

Pages: 14

Price: $28.00