PREPARATION AND PROPERTIES OF SELF-HEALING CARBON FIBER REINFORCED - PDF document

18 TH INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS PREPARATION AND PROPERTIES OF SELF-HEALING CARBON FIBER REINFORCED EPOXY COMPOSITE Rongguo Wang 1* , Honglin Hu 1 , Wenbo Liu 2 , Chengqin Dai 3 , Xiaodong He 1 , Sai Wang 1 1 Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin, 150080,China; 2 School of Materials science and Engineering, Harbin Institute of Technology, Harbin, 150080, China; ; 3 Network and Information Center, Harbin Institute of Technology, Harbin, 150080, China *Corresponding author(wrg@hit.edu.cn) Keywords : epoxy, self-healing efficiency, tensile strength, flexural strength, composite 1 Introduction curing agent was concluded. SEM photographs of Inside cracks in structural composites is hard to be fractured surface of self-healing composite of virgin detected and repaired. Therefore, active polymeric and healed specimen are observed to provide an materials incorporating self-healing functionality intuitional judgment for the self-healing process. have attracted more and more attention because they The recovery of tensile strength carbon fiber represent a new paradigm for structural materials reinforced epoxy composite were investigated so as that require long-term durability and reliability. [1-8] to provide parameters for making self-healing Many of works have focused on binary self-healing composite products. system such as endo-dicyclopentadiene and its 2 Materials and Methods catalysts[1, 9-13], epoxy and its curing agents[5, 6, 2.1 Materials 14]. In this paper, self-healing carbon fiber reinforced epoxy composite was prepared using Epoxy resin (diglycidyl ether of bisphenol A: binary healing system consisting of epoxy- DGEBPA, E-51) used as core material and matrix of containing microcapsules and imidazoline composite was purchased from Wuxi Resin Plant, derivatives curing agent based on anionic China. Epoxy-containing microcapsules were polymerization. When crack propagates along the synthesized via situ-polymerization of urea and interface of carbon fiber and matrix in the composite, formaldehyde in an oil-in-water emulsion. 2,4- the embedded microcapsule is ruptured and the diamino-6-[2’-methyl imidazolyl-(1)’]-ethyl-triazine epoxy healing agent flows out as result of capillary (2MZ-AZINE) used as anionic hardener was action. Finally, polymerization of healing agent obtained from Shikoku Chemical Corporation, Japan. occurs to bond cracks due to the contact with Triethylenetetramine (TETA) used as curing agent embedded hardener. The imidazoline derivatives of matrix was purchased from Tianjin Yixin curing agent used in this study is latent curing agent Tenglong Chemical Plant, China. All the materials which can be well dispersed in epoxy matrix during are commercial products and were used without composite manufacturing. The microcapsules used further purification. in binary healing system are prepared by situ 2.2 Preparation of self-healing carbon fiber polymerization of urea and formaldehyde in an oil- reinforced epoxy composite in-water emulsion. The microcapsules possess rough surface morphology, less adhesion, less core The resin mixture was prepared by mixing 100 parts material permeability, appropriate diameter and core E-51 epoxide with 13 parts TETA curing agent. content, and adequate stability. In this paper, the Then, the microcapsules and 2MZ-AZINE curing protocol of interlaminar healing efficiency of agent were added to the resin mixture under composite was proposed and self-healing ultrasonic agitation . Then the mixture was degassed performance was evaluated. In our former work, it in a vacuum oven. The self-healing composite was was found that the distribution of microcapsules and fabricated by winding process on the flat plate mold. latent curing agent greatly influences the healing Solvent is not used in the work of fabricating efficiency but not the stoichiometric composition, composite. Resultant composite was degassed in a and the optimal weight ratio of microcapsules and

PREPARATION AND PROPERTIES OF SELF-HEALING CARBON FIBER REINFORCED EPOXY COMPOSITE vacuum oven for 30min. Eventually, composite was 24.40873 7.06431 3 28.9 cured for 48h at room temperature, followed by postcuring at 80 ℃ for 1h. 21.79413 10.00964 4 45.9 2.3 Characterization 20.49706 11.50804 5 56.1 Fractured surface of self-healing carbon fiber reinforced epoxy composite was observed by SEM average 31.98 (QUANTA 200 ESEM, FEI). Samples were The average self-healing efficiency in this research prepared on an aluminium slice, dried in a vacuum is 31.98% recovery of interlaminar tensile stress. oven, and sputtered a coat with gold-palladium. Table 1 shows the interlaminar tensile stress and To evaluate recovery of interlaminar properties of self-healing properties of carbon fiber reinforced composites containing microcapsules and hardener, epoxy composite. Figure 1 shows SEM photographs of Five samples were tested. In our former work, the fractured surface of self-healing composite. From Fig. 1 optimal weight ratio of microcapsules and curing (a), the rough microcapsule’s shell edge inlaid into agent 2MZ-AZINE are 15 wt% and 2 wt% for epoxy matrix can be obviously observed, which is caused resin, offering a ~83% healing efficiency.[15] The by the release of healing agent and leaving an empty healing Efficiency is defined as the ratio of tensile microcapsule’s shell. Additionally, the interface join stress, K IC , of healed and virgin materials. The between microcapsules and matrix is strong due to epoxy composite were measured according to the the mechanical engagement of microcapsule’s shell Chinese standard GB/T 1447-1983. A tester that possesses rough outside. As is shown in Fig. 1 (INSTRON 5569) was used at a crosshead speed of 2 (b), compared with virgin specimen, the fractured mm/min. Five samples (180 mm in length, 5 mm in surface of healed specimen is smooth and covered thickness and 10 mm in width) were tested for each with polymer film, which infers that self-healing case. The original specimens were tested to failure, giving the tensile stress, K 0 process is successfully achieved. IC . Load was then removed, allowing the crack faces to come back into contact and to be self-healed in an oven preset at 120 ℃ for 2h. The healed specimens were tested Microcapsule K 1 again and yielded the tensile stress, IC . Accordingly, the crack healing efficiency η can be calculated by (1) O K η = IC 1 K (1) IC 3 Results and Discussion Microcapsule’s shell Self-healing process Carbon fiber Table 1 Interlaminar tensile stress and self-healing properties of carbon fiber reinforced epoxy composite Healing Sample virgin(MPa) healed(MPa) efficiency No. (%) 24.04127 4.31812 1 18.0 23.76047 2.60031 2 11.0