## 1 Introduction
### Literature Review and Previous Work  
Additive manufacturing, also called 3D printing, rapid prototyping, or solid-freeform, known as a \"process of joining materials to make objects from the three-dimensional model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies,\" was first described in 1986, by [PERSON] [10]. Over the past 20 years, AM-printed parts have been applied in automotive cooling systems, various consumer commodities, architectural designs, and engine components in airplanes, to name a few. Several novel AM methods have also been developed during this time. However, the AM of polymer composites has lately drawn significant attention from researchers in academia, as well as industry, for its potential to create lightweight and high-strength structures paired with low production-line costs and greater production flexibility and agility. The AM of fiber-reinforced polymer composites has been found to effectively enhance the mechanical properties of printed parts compared to unreinforced polymer parts [6]. In addition, long fiber (10-25 mm) reinforcement offers improved strength and stiffness compared to unreinforced and short fiber (0.2-0.4 mm) reinforced composites [11]. Despite the increased strength possessed by CFRP composites, common problems prevailing in 3D-printed polymer composites are voids, the lack of proper adhesion between the matrix and the fiber, interlayer gaps or air traps, low fiber-volume fractions, etc. [12]. Continuous carbon-fiber-reinforced polymer (C-CFRP) composites were recently introduced into 3D printing due their significantly better tensile strength compared with 3D-printed CFRP parts, consisting of either long or short fibers; however, the lack of appropriate consolidation techniques makes current 3D-printed C-CFRP parts substantially weaker than C-CFRP parts manufactured using traditional methods [13]. The main challenges in the field of the AM of polymer \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt}} \hline \hline AM & Additive manufacturing \\ \hline C-CFRP & Continuous carbon-fiber-reinforced polymer \\ \hline CFRP & Carbon-fiber-reinforced polymer \\ \hline CFRTCs & Continuous fiber-reinforced thermoplastic composites \\ \hline CNF & Carbon nanofiber \\ \hline COV & Coefficient of variance \\ \hline DM & Distribution medium \\ \hline FDM & Fused deposition modeling \\ \hline FVF & Fiber volume fraction \\ \hline HSM & High shear mixing \\ \hline ILSS & Interlaminar shear strength \\ \hline LOM & Laminated object manufacturing \\ \hline MCA-AM & Magnetic compaction force-assisted additive manufacturing \\ \hline OOA-VBO & Out-of-autoclave vacuum-bag-only molding process \\ \hline RFA & Radial flow alignment \\ \hline RTM & Resin-transfer molding \\ \hline SBS & Short-beam shear test \\ \hline SLS & Selective laser sintering 3D-printing process \\ \hline TTP-WOC-AM & Tension-tape-placement-without-compaction additive manufacturing \\ \hline ZT-CFRP & Z-Threaded carbon-fiber-reinforced polymer \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Technical Acronyms. composites are the lack of comprehensive 3D-printing technologies, suitable advanced polymer materials, and compatible nanomaterial technologies that meet or exceed the performance and fabrication requirements of traditional CFRP-manufacturing standards. A few AM methods are used to print polymer composites. These include fused deposition modeling (FDM), selective laser sintering (SLS), stereolithography (SL), laminated object manufacturing (LOM), and extrusion (modified FDM). In FDM, filaments (which can be pure polymers or polymer composites containing reinforcing fibers/particles) melt into a semi-liquid state and are extruded through a nozzle layer by layer onto a built platform (i.e., a 3D-printer bed, pre-heated to a temperature that allows the filament to adhere properly). The layers are then fused together and eventually solidified into finished parts.