## 1 Introduction  
For a long time, many parts of transportation vehicles and moving structures, such as aircraft wings and wind turbine blades, have been replaced from metal to fiber-reinforced plastics for the purpose of lightweighting for energy efficiency. Fiber-reinforced plastics have a high strength-to-weight ratio, which allows for the lightweighting of products [1, 2, 3]. However, it is challenging to manufacture all parts using fiber-reinforced plastic alone, and sometimes it is advantageous to use them together with metal to utilize metal properties such as electrical conductivity and thermal conductivity. Therefore, research on bonding dissimilar materials such as carbon-fiber-reinforced plastics (CFRPs) with steel and aluminum has gained increasing interest [3, 4]. [PERSON] et al. investigated the bond characteristics of CFRP/steel to strengthen existing steel structures [3], and [PERSON] et al. studied the delamination of CFRP/aluminum hybrid composite tube to increase impact resistance [4]. Metals that are similar materials can be bonded together through welding or soldering, but in the case of metals and polymers, this type of connection is impossible. Bonding methods of dissimilar materials are divided into mechanical joining and chemical bonding. Research on mechanical joining is roughly divided into two categories. The first category includes research on mechanical fasteners that are stable even under stress concentration at joints [5; 6]. The second category includes research on tool technology that is fast and simple, such as friction stir welding for joining thermoplastic composite materials and Al [7; 8]. Among mechanical fasteners, the typical method of mechanical joining, which has been investigated extensively, involves the use of bolts and nuts [9; 10]. Although many bolting studies have been conducted, they have been almost exclusively limited to metals [11; 12]. With the increasing use of composite materials with anisotropic properties, unlike metals, structural deformation and fracture during bonding of composite materials are being studied [13; 14]. [PERSON] investigated the joint failure based on various joint types such as skin thickness, liquid shim thickness, bolt pretension, and lateral support [15]. Considerable efforts are being made to determine a suitable bolting procedure with CFRP as the base material [16]. In particular, when an external load is applied, the joint strength changes depending on the bolting conditions and shape. Since these changes can cause a major defect in structure, further research is needed to investigate their correlation [17; 18; 19; 20]. A representative method other than bolting is the riveeting technique that is capable of automating the joining process using rivets [21]. Rivets are available in various compositions and shapes, for example, aluminum rivets, steel rivets, and structural blind rivets. A typical rivet used for riveting is a blind rivet, which achieves different joint strengths depending on the riveting conditions and shapes; therefore, further correlation studies on riveting are also needed [22]. The major disadvantage of mechanical bonding is that a hole must be created in the base material [23]. Holes are difficult to create, and even if they are created, problems such as clearance occur [24]. Clearance between the hole and fastener is unavoidable in mechanical bonding methods such as bolting and riveting in which the fastener is inserted into the hole and fastened. Currently, a method involving the use of self-piercing riveted (SPR) joints and \(Z\)-pins, in which a pin is inserted by pressing the fastener with a strong pressure on the base material, is being examined to minimize the problems caused by holes [25; 26]. However, several factors must be considered to achieve satisfactory performance. For example, CFRP contains several fiber filaments that have been reinforced [27], but the fibrous tissue using SPR cannot be cut without creating a hole in advance. Thus, the fastening segment inevitably cracks [28; 29].