## 1 Introduction  
Carbon fiber reinforced plastic (CFRP) has been widely used as an important material for industry applications due to its excellent characteristics, such as high strength to weight ratio, excellent fatigue resistance, and little corrosion [1, 2]. The application of CFRP-metal structures for industry applications is also very promising. Aluminum alloys are widely applied in the aircraft and automotive industries, which need lightweight and highly corrosion resistant parts. Due to the advantages of CFRP and aluminum alloys, joining these two materials to produce hybrid components with high functional flexibility has attracted manufacturers' interests. Both CFRP and aluminum alloys are extensively used in the aircraft and automobile industries. However, joining CFRP and aluminum alloys is still a challenging issue due to the very different chemical and physical properties between these materials. A number of joining methods have been used for joining CFRP-aluminum alloys, such as adhesive joining [3], friction stir joining [4], ultrasonic joining [5] and laser joining [6]. Adhesive joining is a conventional process for joining plastics, including CFRP to metals [7]. [PERSON] et al. investigated the surface treatment of CFRP and aluminum to improve the fracture toughness of adhesively-bonded CFRP-aluminum joints [8]. Ar\({}^{+}\) ion irradiation and plasma treatment were performed on the surface of CFRP and aluminum. Scanning electron microscopy (SEM) examination of fracture surfaces showed that the toughness increased by 72% when CFRP was treated by Ar\({}^{+}\) ion irradiation. The fracture load of ion beam-treated CFRP/untreated aluminum can reach 16 kN, and the shear strength is about 5 MPa. [PERSON] et al. applied friction stir blind riveting to join CFRP to aluminum alloy plates [4]. They found that brittle delamination of the CFRP sheet caused a 10% reduction in the maximum tensile loads of the CFRP-aluminum joints. [PERSON] et al. described joining aluminum-wrought alloy (AA 5754) to CFRP with polyamide 66 matrix [9]. Microstructure characterization showed that an intensive connection between AA 5754 and CFRP had developed, and no damage of the CFRP was observed. A tensile shear strength of about 30 MPa was determined for AA 5754/CFRP-PA 66 joints. Besides those traditional joining methods, laser joining has also attracted much interest due to its low thermal effect, noncontacting and high efficiency [10]. [PERSON] et al. investigated the laser joining process of joining polyethylene terephthalate (PET) to a titanium plate [11]. The highest failure stress of the laser joining process was about 10 MPa. [PERSON] et al. reported that with the laser-assisted laser joining of a thermosetting matrix CFRP to polycarbonate (PC), the effective strength of the joints reached 8.4 MPa, which is comparable to the results of 9 MPa obtained by the adhesive joining process [12]. [PERSON] et al. joined polyacrylonitrile-type CFRP to aluminum alloy using a continuous wave diode laser with a line-shaped beam [13]. The tensile shear load of the joints was about 3000 N, and the corresponding shear strength was less than 10 MPa. Recently, reactive multilayer films (RMFs) have attracted much attention for applications in joining processes. RMFs are especially attractive for aerospace or underwater joining and repairing [14; 15]. RMFs can provide energy as a local heat source due to the heat released by the exothermic reaction of the multilayers to form intermetallic compounds [16]. The reaction can be ignited by electrical, thermal, laser pulse, or mechanical striking. For joining purposes, the RMF was placed between two similar or dissimilar materials/components with two layers of preset or precoated solder [17]. [PERSON] et al. used freestanding Ni/Al RMF to melt AuSn solder layers and thereby joined aluminum specimens under pressure of 100 MPa [18]. The shear strength of 32 MPa indicated that AuSn solder should be fully molten for at least 0.5 ms to ensure a full wetting and establish strong joints.