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Abstract
Acrylate functionalities were grafted at the surface of carbon fibers in order to improve the adhesion strength with an acrylate matrix cured by electron beam. An isocyanate bearing aliphatic urethane acrylate was used as a coupling agent. As revealed by X-ray photoelectron spectroscopy, the isocyanate groups reacted with carboxylic acids and hydroxyl groups located at the surface of the fiber, leading to a covalent bonding of the acrylate groups. The adhesion strength was measured by a micromechanical test derived from the pull-out test. A significant improvement of the interfacial shear strength was obtained (+91%) with an electron beam curing. For comparison, an isothermal cure by UV was also investigated and led to the same level of adhesion strength. The improvement was also proved by an increase in the 90° flexural strength of unidirectional composites (+38%). Grafting functionalities that were compatible with the radical mechanism of the polymerization of the matrix appeared to be a promising strategy for the improvement of the mechanical properties of carbon fiber–acrylate composites cured by electron beam.
Acknowledgements
ANRT (Association Nationale de la Recherche et de la Technologie) is gratefully acknowledged for the PhD grants assigned to F. Vautard. Ciba® is sincerely thanked for supplying the photoinitiator used in this study. Bayer MaterialScience LLC is sincerely thanked for the providing of the UA VP LS Roskydal 2337. X. Dupont and M. Frayssines from EADS are also acknowledged for conducting the electron beam curing UNIPOLIS facility. P. Ponsaud is also acknowledged for his contribution to this study, especially for the mechanical data obtained with unidirectional composites presented in this study.