Co-authors​ :

 Seirann MURATA , Takeshi EGUCHI , Kazuaki NISHIYABU (JAPAN) 

The demand for CFRP materials in large structures is rapidly increasing due to its light weight, high strength, and high corrosion resistance. CFRP includes CFRTS (carbon fiber reinforced thermosetting plastic) and CFRTP (carbon fiber reinforced thermosetting plastic), and various joining methods have been developed. For joining CFRTS, chemical bonding by adhesion is suitable, and for joining CFRTP, fusion bonding method, in which thermoplastic resin is melted by some kind of heating and solidified by cooling, is suitable. However, fusion bonding is difficult to disassemble and is vulnerable to fatigue and impact loading, resulting in low joint strength reliability. On the other hand, mechanical fastening using bolts and rivets is easy to disassemble and highly durable, resulting in high joint strength reliability. However, damage due to stress concentration in the drilled hole, increased weight due to the fastening member, and corrosion due to the use of dissimilar intermate rials are problems. Therefore, multi-joining using fusion bonding and mechanical fastening is useful, and riveting methods have been developed to reduce weight and improve corrosion resistance, such as riveting CFRTP round rods by heating them with electric current or by heating them with near-infrared heaters. The riveting method using electric current has the advantage that there is no gap between the rivet shank and the drilled part, but excessive heating may cause voids to form in the CFRTP round rods [1]. The near-infrared heater fastening method has the advantage of being non-contact, compact, and lightweight, making it easy to adopt for use in robots, but it is not suitable for fastening large-diameter round rods because it heats the CFRTP round rods from the surface and does not heat the inside sufficiently [2][3]. The authors also developed a CFRTP round rods head thermoforming method using a ring-type heater. This heating method is useful because the heating is concentrated, and the melting point is reached only at the necessary points for head thermoforming [4].
In this study, CF/PEEK round rods with different fiber orientations were prepared by twisting CF/PEEK prepreg tapes using a laboratory-scale thermal pultrusion machine as shown in Fig.1. Also, a new type of rivet fastening apparatus were developed originally using two compact servo-press units at upper and lower sides and CF/PEEK round rod was moved to a head thermoformed die after heating in the die installed a ring-type cartridge heater as shown in Fig.2. This apparatus is characterized using upper and lower servo-press, which allow simultaneous upper and lower rivet heads thermoforming and individual control and monitoring of the thermoforming load. CF/PEEK fastening behavior and the effect of fiber orientation were investigated by load-displacement curves and single lap shear test of CF/PEEK laminates fasten by CF/PEEK rivet.