Evaluation of strength of resistance welding joints of thermoplastic carbon fiber reinforced composite by using carbon nanotube sheet heater

抄録

Recently, carbon fiber reinforced thermoplastics (CFRTP) have been attracting attention from the viewpoint of reducing the weight of transportation vehicles. To apply CFRTP as structural members, it is necessary to join a CFRTP member with another CFRTP member. Mechanical joining using bolts and nuts is widely used to join CFRTP members but there are problems such as increased weight, limited design freedom, and stress concentration at bolt holes. Adhesive bonding is another method, but it requires time to bond, and it is difficult to bond CFRTP with general adhesives because of the difficulty in obtaining strong chemical bond. In this study, we focus on resistance welding. Resistance welding is a joining method in which thermoplastic film s and a mesh-like resistance heating element are placed between the adherends and a voltage is applied to the resistance heating element to generate heat, resulting in melting and solidification of the films and matrix. In this study, CFRTP joints were fabricated by using a carbon nanotube sheet as a Joule heating element, and single-lap shear strengths and out-of-plane tensile strengths were evaluated. As a result, it was confirmed that the normalized shear strength averaged about 2.5 for the glass transition temperature +148°C or above, implying the shear strength was sufficient. The normalized out-of-plane tensile strengths averaged about 0.3. Since the out-of-plane tensile strength is generally a few tenths of the shear strength, the out-of-plane tensile strength seems to be reasonable.