## 1 Introduction
### Literature Review and Previous Work
The disadvantages of FDM printing are the need for composite materials to be in filament form to enable the extrusion process and the difficulty in dispersing the reinforcements uniformly. Furthermore, a substantial number of voids form, since the printing is performed without any pressure, and the usable materials are limited to thermoplastic polymers with suitable melt viscosities and handleability [14]. At higher temperatures than those suggested, some filaments boil the moisture inside and create air bubbles. Despite these drawbacks, FDM methods offer advantages, such as their low cost and the simplicity of their manufacturing process. Another advantage of FDM is the potential to facilitate deposition of diverse materials simultaneously. Furthermore, FDM methods can be modified to print continuous carbon-fiber-reinforced polymer composites by using continuous carbon-fiber-reinforced polymers (with either a thermoplastic or a thermoset matrix), which are significantly stronger than polymer composites reinforced with discontinuous short or long carbon fibers, such as those used in the other 3D-printing processes. Among all traditional composite-manufacturing methods, processes related to molding, injection, and extrusion are more prevalent. For manufacturing complex-shaped C-CFRP parts, the molding processes are the most suitable. The most notable traditional molding methods are out-of-autoclave vacuum-bag-only (OOA-VBO), autoclave curing, compression molding, reaction-injection molding, resin-transfer molding, elastic reservoir molding, and resin-film infusion. The mechanical properties of a molded part depend on many factors, such as the degree of cure, fiber-alignment precision, quality of the raw materials, and presence of molding defects. Quality can be improved by proper part and mold designs to prevent dry spots and void formation, although these voids cannot be prevented entirely [15]. It is paramount that the molded parts are inspected on a regular basis to prevent premature failure. In addition, all molding processes require intensive handling and preparation, along with cleaning and mold-tool storage and maintenance after long manufacturing times. While current 3D printing technologies have some processing conveniences and advantages compared to traditional composite-manufacturing methods, the majority of 3D-printing methods cannot manufacture C-CFRP parts as strong as their counterparts manufactured using traditional methods. Table 1 compares some published data [16; 17; 18] on C-CFRP parts printed by already-improved 3D-printing methods to their counterparts manufactured using either traditional composite-manufacturing methods (such as the autoclave method and the OOA-VBO method) or typical FDM 3D printing. In terms of interlaminar shear strength (ILSS), the typical 3D-printing method significantly underperformed compared to the traditional composite-manufacturing methods. There is a need for a new AM technique that incorporates the conveniences and advantages of current 3D-printing methods and the strength and performance of composite parts manufactured by traditional methods. Table 2 also indicates that even with improved 3D-printing methods, the ILSS of 3D-printed CFRP parts is still either less than or, at best, equal to the ILSS of CFRPs produced by traditional composite-manufacturing methods. Traditional manufacturing methods usually involve ideal processing parameters, such as the use of high compression pressure to press the prepreg laminas together, and the use of high levels of vacuum to remove gas and volatiles, which can form voids. Furthermore, traditional methods usually employ slow and uniform temperature-control cycles during the resin-curing process, substantially reducing the process-induced residual stress on the CFRP parts [19]. As shown in Table 2, the MCFA-AM method produced C-CFRP parts with ILSS values very close to those of their counterparts produced by the OOA-VBO process.