A novel joining method by using carbon nanotube-based thermoplastic film for injection over-molding process

• Published in: Journal of reinforced plastics and composites 2019-07, Vol.38 (13), p.616-627
• Main Authors: Matsumoto, Koki, Ishikawa, Takeshi, Tanaka, Tatsuya
• Format: Article
• Language: English
• ISSN: 0731-6844; 1530-7964
• DOI: 10.1177/0731684419838070

Hybrid thermoplastic composites are getting attention in light weight applications. The manufacturing process of hybrid composites is that discontinuous fiber-reinforced thermoplastics are injected onto the textile-reinforced thermoplastics through injection over-molding. The key topic of this process is to achieve a reliable interfacial bonding strength, which has a strong dependence on the molding conditions. As a novel approach, we adopted a carbon nanotube-based thermoplastic film to make nanoscale interconnections between different layers by inserting films between the layers. In this work, the following influences were investigated with respect to the interlaminar shear strength by short beam shear test: the (i) existence, (ii) dispersion state, (iii) concentration of carbon nanotubes, and (iv) injection over-molding conditions. Furthermore, the delaminated surface after short beam shear test was assessed via SEM observation. Consequently, polypropylene-injected hybrid composite with 1 wt% carbon nanotubes exhibited a 52% increase in interlaminar shear strength compared with the specimen without carbon nanotubes. Additionally, the combination of short carbon fibers, which were filled in injected polypropylene, and carbon nanotubes drastically enhanced the interlaminar shear strength. The optimization of carbon nanotube dispersion and molding condition provides strong improvement of interlaminar shear strength. However, excessive addition of carbon nanotube deteriorates the interlaminar shear strength.