13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Evaluation of Strength Recovery and Analysis of Damage Progression of Notched Unidirectional Carbon/Epoxy Composites Encompassing Self-Healing of Interfacial Debonding Kazuaki Sanada1,*, Yuta Mizuno1, Yasuhide Shindo2 1 Department of Mechanical Systems Engineering, Toyama Prefectural University, Toyama 939-0398, Japan 2 Department of Materials Processing, Graduate School of Engineering, Tohoku University, Sendai 980-8597, Japan * Corresponding author: sanada@pu-toyama.ac.jp Abstract This study examines the interfacial debonding behavior of self-healing fiber reinforced polymers (FRPs) and the performance of repair of interfacial debonding. Self-healing is accomplished by incorporating a microencapsulated healing agent and a catalyst within a coating layer on the surface of the fiber strand. Single edge notched tensile (SENT) specimens of unidirectional FRPs with coated fiber strands were prepared and tested. The healing efficiency was evaluated by the critical fracture loads of virgin and healed specimens. To investigate the release of the healing agent from microcapsules during interfacial debonding, an ultra-violet (UV) fluorescent dye was added to the healing agent and post-fracture specimens were examined by an optical microscope under UV light. In addition to conducting experiments, finite element analyses were performed using a three-dimensional model to predict the damage progression in SENT specimens. Keywords Interface mechanics, Composite materials, Notched tensile strength, Damage progression, Self-healing 1. Introduction Interfacial debonding can cause a reduction in strength and stiffness of fiber-reinforced polymers (FRPs) and is extremely difficult to detect and repair by conventional methods. Thus, self-healing has the potential to mitigate the interfacial debonding. Although many studies have addressed the self-healing of internal damage in FRPs, there are few reports on the self-healing of interfacial debonding. Sanada et al. [1] proposed a methodology for self-healing of interfacial debonding in unidirectional FRPs by using fiber strands coated with the self-healing polymer developed by White et al. [2] and conducted transverse tensile tests to assess the self-healing efficiency. Also, Sanada et al. [3] investigated the effect of microstructure on the efficiency of transverse tensile strength recovery of self-healing FRPs. The maximum healing efficiency achieved with these specimens was about 20% and the low healing efficiency achieved was due to complete rupture of virgin specimens. Blaiszik et al. [4] performed a microbond test using a single fiber coated with DCPD-filled microcapsules and Grubbs catalyst, and assessed the recovery of interfacial shear strength. The aim of this study is to investigate the interfacial debonding behavior of self-healing FRPs and to assess the performance of self-healing system for interfacial debonding. Tensile tests were carried out with single edge notched tensile (SENT) specimens of unidirectional FRPs containing fiber strands coated with DCPD-filled microcapsules and Grubbs catalyst, and healing efficiency was calculated using the critical fracture loads of virgin and healed specimens. Fluorescent labeling of damage in post-fracture specimens was performed to study the release of DCPD from microcapsules during interfacial debonding. Additionally, finite element analyses were employed to study the effect of specimen thickness and coating properties on the damage progression in SENT specimens.
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